whatcanGOwrong

go/pkg/mod/golang.org/x/mod@v0.14.0/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

go/pkg/mod/golang.org/x/mod@v0.14.0/PATENTS

@@ -0,0 +1,22 @@
+Additional IP Rights Grant (Patents)
+
+"This implementation" means the copyrightable works distributed by
+Google as part of the Go project.
+
+Google hereby grants to You a perpetual, worldwide, non-exclusive,
+no-charge, royalty-free, irrevocable (except as stated in this section)
+patent license to make, have made, use, offer to sell, sell, import,
+transfer and otherwise run, modify and propagate the contents of this
+implementation of Go, where such license applies only to those patent
+claims, both currently owned or controlled by Google and acquired in
+the future, licensable by Google that are necessarily infringed by this
+implementation of Go.  This grant does not include claims that would be
+infringed only as a consequence of further modification of this
+implementation.  If you or your agent or exclusive licensee institute or
+order or agree to the institution of patent litigation against any
+entity (including a cross-claim or counterclaim in a lawsuit) alleging
+that this implementation of Go or any code incorporated within this
+implementation of Go constitutes direct or contributory patent
+infringement, or inducement of patent infringement, then any patent
+rights granted to you under this License for this implementation of Go
+shall terminate as of the date such litigation is filed.

go/pkg/mod/golang.org/x/mod@v0.14.0/README.md

@@ -0,0 +1,17 @@
+# mod
+
+[![PkgGoDev](https://pkg.go.dev/badge/golang.org/x/mod)](https://pkg.go.dev/golang.org/x/mod)
+
+This repository holds packages for writing tools
+that work directly with Go module mechanics.
+That is, it is for direct manipulation of Go modules themselves.
+
+It is NOT about supporting general development tools that
+need to do things like load packages in module mode.
+That use case, where modules are incidental rather than the focus,
+should remain in [x/tools](https://pkg.go.dev/golang/org/x/tools),
+specifically [x/tools/go/packages](https://pkg.go.dev/golang.org/x/tools/go/packages).
+
+The specific case of loading packages should still be done by
+invoking the go command, which remains the single point of
+truth for package loading algorithms.

go/pkg/mod/golang.org/x/mod@v0.14.0/codereview.cfg

@@ -0,0 +1 @@
+issuerepo: golang/go

go/pkg/mod/golang.org/x/mod@v0.14.0/go.mod

@@ -0,0 +1,5 @@
+module golang.org/x/mod
+
+go 1.18
+
+require golang.org/x/tools v0.13.0 // tagx:ignore

go/pkg/mod/golang.org/x/mod@v0.14.0/go.sum

@@ -0,0 +1,2 @@
+golang.org/x/tools v0.13.0 h1:Iey4qkscZuv0VvIt8E0neZjtPVQFSc870HQ448QgEmQ=
+golang.org/x/tools v0.13.0/go.mod h1:HvlwmtVNQAhOuCjW7xxvovg8wbNq7LwfXh/k7wXUl58=

go/pkg/mod/golang.org/x/mod@v0.14.0/gosumcheck/main.go

@@ -0,0 +1,211 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Gosumcheck checks a go.sum file against a go.sum database server.
+//
+// Usage:
+//
+//	gosumcheck [-h H] [-k key] [-u url] [-v] go.sum
+//
+// The -h flag changes the tile height (default 8).
+//
+// The -k flag changes the go.sum database server key.
+//
+// The -u flag overrides the URL of the server (usually set from the key name).
+//
+// The -v flag enables verbose output.
+// In particular, it causes gosumcheck to report
+// the URL and elapsed time for each server request.
+//
+// WARNING! WARNING! WARNING!
+//
+// Gosumcheck is meant as a proof of concept demo and should not be
+// used in production scripts or continuous integration testing.
+// It does not cache any downloaded information from run to run,
+// making it expensive and also keeping it from detecting server
+// misbehavior or successful HTTPS man-in-the-middle timeline forks.
+//
+// To discourage misuse in automated settings, gosumcheck does not
+// set any exit status to report whether any problems were found.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/mod/sumdb"
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: gosumcheck [-h H] [-k key] [-u url] [-v] go.sum...\n")
+	os.Exit(2)
+}
+
+var (
+	height = flag.Int("h", 8, "tile height")
+	vkey   = flag.String("k", "sum.golang.org+033de0ae+Ac4zctda0e5eza+HJyk9SxEdh+s3Ux18htTTAD8OuAn8", "key")
+	url    = flag.String("u", "", "url to server (overriding name)")
+	vflag  = flag.Bool("v", false, "enable verbose output")
+)
+
+func main() {
+	log.SetPrefix("notecheck: ")
+	log.SetFlags(0)
+
+	flag.Usage = usage
+	flag.Parse()
+	if flag.NArg() < 1 {
+		usage()
+	}
+
+	client := sumdb.NewClient(new(clientOps))
+
+	// Look in environment explicitly, so that if 'go env' is old and
+	// doesn't know about GONOSUMDB, we at least get anything
+	// set in the environment.
+	env := os.Getenv("GONOSUMDB")
+	if env == "" {
+		out, err := exec.Command("go", "env", "GONOSUMDB").CombinedOutput()
+		if err != nil {
+			log.Fatalf("go env GONOSUMDB: %v\n%s", err, out)
+		}
+		env = strings.TrimSpace(string(out))
+	}
+	client.SetGONOSUMDB(env)
+
+	for _, arg := range flag.Args() {
+		data, err := os.ReadFile(arg)
+		if err != nil {
+			log.Fatal(err)
+		}
+		checkGoSum(client, arg, data)
+	}
+}
+
+func checkGoSum(client *sumdb.Client, name string, data []byte) {
+	lines := strings.Split(string(data), "\n")
+	if lines[len(lines)-1] != "" {
+		log.Printf("error: final line missing newline")
+		return
+	}
+	lines = lines[:len(lines)-1]
+
+	errs := make([]string, len(lines))
+	var wg sync.WaitGroup
+	for i, line := range lines {
+		wg.Add(1)
+		go func(i int, line string) {
+			defer wg.Done()
+			f := strings.Fields(line)
+			if len(f) != 3 {
+				errs[i] = "invalid number of fields"
+				return
+			}
+
+			dbLines, err := client.Lookup(f[0], f[1])
+			if err != nil {
+				if err == sumdb.ErrGONOSUMDB {
+					errs[i] = fmt.Sprintf("%s@%s: %v", f[0], f[1], err)
+				} else {
+					// Otherwise Lookup properly adds the prefix itself.
+					errs[i] = err.Error()
+				}
+				return
+			}
+			hashAlgPrefix := f[0] + " " + f[1] + " " + f[2][:strings.Index(f[2], ":")+1]
+			for _, dbLine := range dbLines {
+				if dbLine == line {
+					return
+				}
+				if strings.HasPrefix(dbLine, hashAlgPrefix) {
+					errs[i] = fmt.Sprintf("%s@%s hash mismatch: have %s, want %s", f[0], f[1], line, dbLine)
+					return
+				}
+			}
+			errs[i] = fmt.Sprintf("%s@%s hash algorithm mismatch: have %s, want one of:\n\t%s", f[0], f[1], line, strings.Join(dbLines, "\n\t"))
+		}(i, line)
+	}
+	wg.Wait()
+
+	for i, err := range errs {
+		if err != "" {
+			fmt.Printf("%s:%d: %s\n", name, i+1, err)
+		}
+	}
+}
+
+type clientOps struct{}
+
+func (*clientOps) ReadConfig(file string) ([]byte, error) {
+	if file == "key" {
+		return []byte(*vkey), nil
+	}
+	if strings.HasSuffix(file, "/latest") {
+		// Looking for cached latest tree head.
+		// Empty result means empty tree.
+		return []byte{}, nil
+	}
+	return nil, fmt.Errorf("unknown config %s", file)
+}
+
+func (*clientOps) WriteConfig(file string, old, new []byte) error {
+	// Ignore writes.
+	return nil
+}
+
+func (*clientOps) ReadCache(file string) ([]byte, error) {
+	return nil, fmt.Errorf("no cache")
+}
+
+func (*clientOps) WriteCache(file string, data []byte) {
+	// Ignore writes.
+}
+
+func (*clientOps) Log(msg string) {
+	log.Print(msg)
+}
+
+func (*clientOps) SecurityError(msg string) {
+	log.Fatal(msg)
+}
+
+func init() {
+	http.DefaultClient.Timeout = 1 * time.Minute
+}
+
+func (*clientOps) ReadRemote(path string) ([]byte, error) {
+	name := *vkey
+	if i := strings.Index(name, "+"); i >= 0 {
+		name = name[:i]
+	}
+	start := time.Now()
+	target := "https://" + name + path
+	if *url != "" {
+		target = *url + path
+	}
+	resp, err := http.Get(target)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("GET %v: %v", target, resp.Status)
+	}
+	data, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return nil, err
+	}
+	if *vflag {
+		fmt.Fprintf(os.Stderr, "%.3fs %s\n", time.Since(start).Seconds(), target)
+	}
+	return data, nil
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/gosumcheck/test.bash

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+set -e
+go build -o gosumcheck.exe
+export GONOSUMDB=*/text # rsc.io/text but not golang.org/x/text
+./gosumcheck.exe "$@" -v test.sum
+rm -f ./gosumcheck.exe
+echo PASS

go/pkg/mod/golang.org/x/mod@v0.14.0/gosumcheck/test.sum

@@ -0,0 +1,6 @@
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:qgOY6WgZOaTkIIMiVjBQcw93ERBE4m30iBm00nkL0i8=
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/text v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

go/pkg/mod/golang.org/x/mod@v0.14.0/internal/lazyregexp/lazyre.go

@@ -0,0 +1,78 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package lazyregexp is a thin wrapper over regexp, allowing the use of global
+// regexp variables without forcing them to be compiled at init.
+package lazyregexp
+
+import (
+	"os"
+	"regexp"
+	"strings"
+	"sync"
+)
+
+// Regexp is a wrapper around [regexp.Regexp], where the underlying regexp will be
+// compiled the first time it is needed.
+type Regexp struct {
+	str  string
+	once sync.Once
+	rx   *regexp.Regexp
+}
+
+func (r *Regexp) re() *regexp.Regexp {
+	r.once.Do(r.build)
+	return r.rx
+}
+
+func (r *Regexp) build() {
+	r.rx = regexp.MustCompile(r.str)
+	r.str = ""
+}
+
+func (r *Regexp) FindSubmatch(s []byte) [][]byte {
+	return r.re().FindSubmatch(s)
+}
+
+func (r *Regexp) FindStringSubmatch(s string) []string {
+	return r.re().FindStringSubmatch(s)
+}
+
+func (r *Regexp) FindStringSubmatchIndex(s string) []int {
+	return r.re().FindStringSubmatchIndex(s)
+}
+
+func (r *Regexp) ReplaceAllString(src, repl string) string {
+	return r.re().ReplaceAllString(src, repl)
+}
+
+func (r *Regexp) FindString(s string) string {
+	return r.re().FindString(s)
+}
+
+func (r *Regexp) FindAllString(s string, n int) []string {
+	return r.re().FindAllString(s, n)
+}
+
+func (r *Regexp) MatchString(s string) bool {
+	return r.re().MatchString(s)
+}
+
+func (r *Regexp) SubexpNames() []string {
+	return r.re().SubexpNames()
+}
+
+var inTest = len(os.Args) > 0 && strings.HasSuffix(strings.TrimSuffix(os.Args[0], ".exe"), ".test")
+
+// New creates a new lazy regexp, delaying the compiling work until it is first
+// needed. If the code is being run as part of tests, the regexp compiling will
+// happen immediately.
+func New(str string) *Regexp {
+	lr := &Regexp{str: str}
+	if inTest {
+		// In tests, always compile the regexps early.
+		lr.re()
+	}
+	return lr
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/print.go

@@ -0,0 +1,184 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Module file printer.
+
+package modfile
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+)
+
+// Format returns a go.mod file as a byte slice, formatted in standard style.
+func Format(f *FileSyntax) []byte {
+	pr := &printer{}
+	pr.file(f)
+
+	// remove trailing blank lines
+	b := pr.Bytes()
+	for len(b) > 0 && b[len(b)-1] == '\n' && (len(b) == 1 || b[len(b)-2] == '\n') {
+		b = b[:len(b)-1]
+	}
+	return b
+}
+
+// A printer collects the state during printing of a file or expression.
+type printer struct {
+	bytes.Buffer           // output buffer
+	comment      []Comment // pending end-of-line comments
+	margin       int       // left margin (indent), a number of tabs
+}
+
+// printf prints to the buffer.
+func (p *printer) printf(format string, args ...interface{}) {
+	fmt.Fprintf(p, format, args...)
+}
+
+// indent returns the position on the current line, in bytes, 0-indexed.
+func (p *printer) indent() int {
+	b := p.Bytes()
+	n := 0
+	for n < len(b) && b[len(b)-1-n] != '\n' {
+		n++
+	}
+	return n
+}
+
+// newline ends the current line, flushing end-of-line comments.
+func (p *printer) newline() {
+	if len(p.comment) > 0 {
+		p.printf(" ")
+		for i, com := range p.comment {
+			if i > 0 {
+				p.trim()
+				p.printf("\n")
+				for i := 0; i < p.margin; i++ {
+					p.printf("\t")
+				}
+			}
+			p.printf("%s", strings.TrimSpace(com.Token))
+		}
+		p.comment = p.comment[:0]
+	}
+
+	p.trim()
+	if b := p.Bytes(); len(b) == 0 || (len(b) >= 2 && b[len(b)-1] == '\n' && b[len(b)-2] == '\n') {
+		// skip the blank line at top of file or after a blank line
+	} else {
+		p.printf("\n")
+	}
+	for i := 0; i < p.margin; i++ {
+		p.printf("\t")
+	}
+}
+
+// trim removes trailing spaces and tabs from the current line.
+func (p *printer) trim() {
+	// Remove trailing spaces and tabs from line we're about to end.
+	b := p.Bytes()
+	n := len(b)
+	for n > 0 && (b[n-1] == '\t' || b[n-1] == ' ') {
+		n--
+	}
+	p.Truncate(n)
+}
+
+// file formats the given file into the print buffer.
+func (p *printer) file(f *FileSyntax) {
+	for _, com := range f.Before {
+		p.printf("%s", strings.TrimSpace(com.Token))
+		p.newline()
+	}
+
+	for i, stmt := range f.Stmt {
+		switch x := stmt.(type) {
+		case *CommentBlock:
+			// comments already handled
+			p.expr(x)
+
+		default:
+			p.expr(x)
+			p.newline()
+		}
+
+		for _, com := range stmt.Comment().After {
+			p.printf("%s", strings.TrimSpace(com.Token))
+			p.newline()
+		}
+
+		if i+1 < len(f.Stmt) {
+			p.newline()
+		}
+	}
+}
+
+func (p *printer) expr(x Expr) {
+	// Emit line-comments preceding this expression.
+	if before := x.Comment().Before; len(before) > 0 {
+		// Want to print a line comment.
+		// Line comments must be at the current margin.
+		p.trim()
+		if p.indent() > 0 {
+			// There's other text on the line. Start a new line.
+			p.printf("\n")
+		}
+		// Re-indent to margin.
+		for i := 0; i < p.margin; i++ {
+			p.printf("\t")
+		}
+		for _, com := range before {
+			p.printf("%s", strings.TrimSpace(com.Token))
+			p.newline()
+		}
+	}
+
+	switch x := x.(type) {
+	default:
+		panic(fmt.Errorf("printer: unexpected type %T", x))
+
+	case *CommentBlock:
+		// done
+
+	case *LParen:
+		p.printf("(")
+	case *RParen:
+		p.printf(")")
+
+	case *Line:
+		p.tokens(x.Token)
+
+	case *LineBlock:
+		p.tokens(x.Token)
+		p.printf(" ")
+		p.expr(&x.LParen)
+		p.margin++
+		for _, l := range x.Line {
+			p.newline()
+			p.expr(l)
+		}
+		p.margin--
+		p.newline()
+		p.expr(&x.RParen)
+	}
+
+	// Queue end-of-line comments for printing when we
+	// reach the end of the line.
+	p.comment = append(p.comment, x.Comment().Suffix...)
+}
+
+func (p *printer) tokens(tokens []string) {
+	sep := ""
+	for _, t := range tokens {
+		if t == "," || t == ")" || t == "]" || t == "}" {
+			sep = ""
+		}
+		p.printf("%s%s", sep, t)
+		sep = " "
+		if t == "(" || t == "[" || t == "{" {
+			sep = ""
+		}
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/read.go

@@ -0,0 +1,958 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package modfile
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A Position describes an arbitrary source position in a file, including the
+// file, line, column, and byte offset.
+type Position struct {
+	Line     int // line in input (starting at 1)
+	LineRune int // rune in line (starting at 1)
+	Byte     int // byte in input (starting at 0)
+}
+
+// add returns the position at the end of s, assuming it starts at p.
+func (p Position) add(s string) Position {
+	p.Byte += len(s)
+	if n := strings.Count(s, "\n"); n > 0 {
+		p.Line += n
+		s = s[strings.LastIndex(s, "\n")+1:]
+		p.LineRune = 1
+	}
+	p.LineRune += utf8.RuneCountInString(s)
+	return p
+}
+
+// An Expr represents an input element.
+type Expr interface {
+	// Span returns the start and end position of the expression,
+	// excluding leading or trailing comments.
+	Span() (start, end Position)
+
+	// Comment returns the comments attached to the expression.
+	// This method would normally be named 'Comments' but that
+	// would interfere with embedding a type of the same name.
+	Comment() *Comments
+}
+
+// A Comment represents a single // comment.
+type Comment struct {
+	Start  Position
+	Token  string // without trailing newline
+	Suffix bool   // an end of line (not whole line) comment
+}
+
+// Comments collects the comments associated with an expression.
+type Comments struct {
+	Before []Comment // whole-line comments before this expression
+	Suffix []Comment // end-of-line comments after this expression
+
+	// For top-level expressions only, After lists whole-line
+	// comments following the expression.
+	After []Comment
+}
+
+// Comment returns the receiver. This isn't useful by itself, but
+// a [Comments] struct is embedded into all the expression
+// implementation types, and this gives each of those a Comment
+// method to satisfy the Expr interface.
+func (c *Comments) Comment() *Comments {
+	return c
+}
+
+// A FileSyntax represents an entire go.mod file.
+type FileSyntax struct {
+	Name string // file path
+	Comments
+	Stmt []Expr
+}
+
+func (x *FileSyntax) Span() (start, end Position) {
+	if len(x.Stmt) == 0 {
+		return
+	}
+	start, _ = x.Stmt[0].Span()
+	_, end = x.Stmt[len(x.Stmt)-1].Span()
+	return start, end
+}
+
+// addLine adds a line containing the given tokens to the file.
+//
+// If the first token of the hint matches the first token of the
+// line, the new line is added at the end of the block containing hint,
+// extracting hint into a new block if it is not yet in one.
+//
+// If the hint is non-nil buts its first token does not match,
+// the new line is added after the block containing hint
+// (or hint itself, if not in a block).
+//
+// If no hint is provided, addLine appends the line to the end of
+// the last block with a matching first token,
+// or to the end of the file if no such block exists.
+func (x *FileSyntax) addLine(hint Expr, tokens ...string) *Line {
+	if hint == nil {
+		// If no hint given, add to the last statement of the given type.
+	Loop:
+		for i := len(x.Stmt) - 1; i >= 0; i-- {
+			stmt := x.Stmt[i]
+			switch stmt := stmt.(type) {
+			case *Line:
+				if stmt.Token != nil && stmt.Token[0] == tokens[0] {
+					hint = stmt
+					break Loop
+				}
+			case *LineBlock:
+				if stmt.Token[0] == tokens[0] {
+					hint = stmt
+					break Loop
+				}
+			}
+		}
+	}
+
+	newLineAfter := func(i int) *Line {
+		new := &Line{Token: tokens}
+		if i == len(x.Stmt) {
+			x.Stmt = append(x.Stmt, new)
+		} else {
+			x.Stmt = append(x.Stmt, nil)
+			copy(x.Stmt[i+2:], x.Stmt[i+1:])
+			x.Stmt[i+1] = new
+		}
+		return new
+	}
+
+	if hint != nil {
+		for i, stmt := range x.Stmt {
+			switch stmt := stmt.(type) {
+			case *Line:
+				if stmt == hint {
+					if stmt.Token == nil || stmt.Token[0] != tokens[0] {
+						return newLineAfter(i)
+					}
+
+					// Convert line to line block.
+					stmt.InBlock = true
+					block := &LineBlock{Token: stmt.Token[:1], Line: []*Line{stmt}}
+					stmt.Token = stmt.Token[1:]
+					x.Stmt[i] = block
+					new := &Line{Token: tokens[1:], InBlock: true}
+					block.Line = append(block.Line, new)
+					return new
+				}
+
+			case *LineBlock:
+				if stmt == hint {
+					if stmt.Token[0] != tokens[0] {
+						return newLineAfter(i)
+					}
+
+					new := &Line{Token: tokens[1:], InBlock: true}
+					stmt.Line = append(stmt.Line, new)
+					return new
+				}
+
+				for j, line := range stmt.Line {
+					if line == hint {
+						if stmt.Token[0] != tokens[0] {
+							return newLineAfter(i)
+						}
+
+						// Add new line after hint within the block.
+						stmt.Line = append(stmt.Line, nil)
+						copy(stmt.Line[j+2:], stmt.Line[j+1:])
+						new := &Line{Token: tokens[1:], InBlock: true}
+						stmt.Line[j+1] = new
+						return new
+					}
+				}
+			}
+		}
+	}
+
+	new := &Line{Token: tokens}
+	x.Stmt = append(x.Stmt, new)
+	return new
+}
+
+func (x *FileSyntax) updateLine(line *Line, tokens ...string) {
+	if line.InBlock {
+		tokens = tokens[1:]
+	}
+	line.Token = tokens
+}
+
+// markRemoved modifies line so that it (and its end-of-line comment, if any)
+// will be dropped by (*FileSyntax).Cleanup.
+func (line *Line) markRemoved() {
+	line.Token = nil
+	line.Comments.Suffix = nil
+}
+
+// Cleanup cleans up the file syntax x after any edit operations.
+// To avoid quadratic behavior, (*Line).markRemoved marks the line as dead
+// by setting line.Token = nil but does not remove it from the slice
+// in which it appears. After edits have all been indicated,
+// calling Cleanup cleans out the dead lines.
+func (x *FileSyntax) Cleanup() {
+	w := 0
+	for _, stmt := range x.Stmt {
+		switch stmt := stmt.(type) {
+		case *Line:
+			if stmt.Token == nil {
+				continue
+			}
+		case *LineBlock:
+			ww := 0
+			for _, line := range stmt.Line {
+				if line.Token != nil {
+					stmt.Line[ww] = line
+					ww++
+				}
+			}
+			if ww == 0 {
+				continue
+			}
+			if ww == 1 {
+				// Collapse block into single line.
+				line := &Line{
+					Comments: Comments{
+						Before: commentsAdd(stmt.Before, stmt.Line[0].Before),
+						Suffix: commentsAdd(stmt.Line[0].Suffix, stmt.Suffix),
+						After:  commentsAdd(stmt.Line[0].After, stmt.After),
+					},
+					Token: stringsAdd(stmt.Token, stmt.Line[0].Token),
+				}
+				x.Stmt[w] = line
+				w++
+				continue
+			}
+			stmt.Line = stmt.Line[:ww]
+		}
+		x.Stmt[w] = stmt
+		w++
+	}
+	x.Stmt = x.Stmt[:w]
+}
+
+func commentsAdd(x, y []Comment) []Comment {
+	return append(x[:len(x):len(x)], y...)
+}
+
+func stringsAdd(x, y []string) []string {
+	return append(x[:len(x):len(x)], y...)
+}
+
+// A CommentBlock represents a top-level block of comments separate
+// from any rule.
+type CommentBlock struct {
+	Comments
+	Start Position
+}
+
+func (x *CommentBlock) Span() (start, end Position) {
+	return x.Start, x.Start
+}
+
+// A Line is a single line of tokens.
+type Line struct {
+	Comments
+	Start   Position
+	Token   []string
+	InBlock bool
+	End     Position
+}
+
+func (x *Line) Span() (start, end Position) {
+	return x.Start, x.End
+}
+
+// A LineBlock is a factored block of lines, like
+//
+//	require (
+//		"x"
+//		"y"
+//	)
+type LineBlock struct {
+	Comments
+	Start  Position
+	LParen LParen
+	Token  []string
+	Line   []*Line
+	RParen RParen
+}
+
+func (x *LineBlock) Span() (start, end Position) {
+	return x.Start, x.RParen.Pos.add(")")
+}
+
+// An LParen represents the beginning of a parenthesized line block.
+// It is a place to store suffix comments.
+type LParen struct {
+	Comments
+	Pos Position
+}
+
+func (x *LParen) Span() (start, end Position) {
+	return x.Pos, x.Pos.add(")")
+}
+
+// An RParen represents the end of a parenthesized line block.
+// It is a place to store whole-line (before) comments.
+type RParen struct {
+	Comments
+	Pos Position
+}
+
+func (x *RParen) Span() (start, end Position) {
+	return x.Pos, x.Pos.add(")")
+}
+
+// An input represents a single input file being parsed.
+type input struct {
+	// Lexing state.
+	filename   string    // name of input file, for errors
+	complete   []byte    // entire input
+	remaining  []byte    // remaining input
+	tokenStart []byte    // token being scanned to end of input
+	token      token     // next token to be returned by lex, peek
+	pos        Position  // current input position
+	comments   []Comment // accumulated comments
+
+	// Parser state.
+	file        *FileSyntax // returned top-level syntax tree
+	parseErrors ErrorList   // errors encountered during parsing
+
+	// Comment assignment state.
+	pre  []Expr // all expressions, in preorder traversal
+	post []Expr // all expressions, in postorder traversal
+}
+
+func newInput(filename string, data []byte) *input {
+	return &input{
+		filename:  filename,
+		complete:  data,
+		remaining: data,
+		pos:       Position{Line: 1, LineRune: 1, Byte: 0},
+	}
+}
+
+// parse parses the input file.
+func parse(file string, data []byte) (f *FileSyntax, err error) {
+	// The parser panics for both routine errors like syntax errors
+	// and for programmer bugs like array index errors.
+	// Turn both into error returns. Catching bug panics is
+	// especially important when processing many files.
+	in := newInput(file, data)
+	defer func() {
+		if e := recover(); e != nil && e != &in.parseErrors {
+			in.parseErrors = append(in.parseErrors, Error{
+				Filename: in.filename,
+				Pos:      in.pos,
+				Err:      fmt.Errorf("internal error: %v", e),
+			})
+		}
+		if err == nil && len(in.parseErrors) > 0 {
+			err = in.parseErrors
+		}
+	}()
+
+	// Prime the lexer by reading in the first token. It will be available
+	// in the next peek() or lex() call.
+	in.readToken()
+
+	// Invoke the parser.
+	in.parseFile()
+	if len(in.parseErrors) > 0 {
+		return nil, in.parseErrors
+	}
+	in.file.Name = in.filename
+
+	// Assign comments to nearby syntax.
+	in.assignComments()
+
+	return in.file, nil
+}
+
+// Error is called to report an error.
+// Error does not return: it panics.
+func (in *input) Error(s string) {
+	in.parseErrors = append(in.parseErrors, Error{
+		Filename: in.filename,
+		Pos:      in.pos,
+		Err:      errors.New(s),
+	})
+	panic(&in.parseErrors)
+}
+
+// eof reports whether the input has reached end of file.
+func (in *input) eof() bool {
+	return len(in.remaining) == 0
+}
+
+// peekRune returns the next rune in the input without consuming it.
+func (in *input) peekRune() int {
+	if len(in.remaining) == 0 {
+		return 0
+	}
+	r, _ := utf8.DecodeRune(in.remaining)
+	return int(r)
+}
+
+// peekPrefix reports whether the remaining input begins with the given prefix.
+func (in *input) peekPrefix(prefix string) bool {
+	// This is like bytes.HasPrefix(in.remaining, []byte(prefix))
+	// but without the allocation of the []byte copy of prefix.
+	for i := 0; i < len(prefix); i++ {
+		if i >= len(in.remaining) || in.remaining[i] != prefix[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// readRune consumes and returns the next rune in the input.
+func (in *input) readRune() int {
+	if len(in.remaining) == 0 {
+		in.Error("internal lexer error: readRune at EOF")
+	}
+	r, size := utf8.DecodeRune(in.remaining)
+	in.remaining = in.remaining[size:]
+	if r == '\n' {
+		in.pos.Line++
+		in.pos.LineRune = 1
+	} else {
+		in.pos.LineRune++
+	}
+	in.pos.Byte += size
+	return int(r)
+}
+
+type token struct {
+	kind   tokenKind
+	pos    Position
+	endPos Position
+	text   string
+}
+
+type tokenKind int
+
+const (
+	_EOF tokenKind = -(iota + 1)
+	_EOLCOMMENT
+	_IDENT
+	_STRING
+	_COMMENT
+
+	// newlines and punctuation tokens are allowed as ASCII codes.
+)
+
+func (k tokenKind) isComment() bool {
+	return k == _COMMENT || k == _EOLCOMMENT
+}
+
+// isEOL returns whether a token terminates a line.
+func (k tokenKind) isEOL() bool {
+	return k == _EOF || k == _EOLCOMMENT || k == '\n'
+}
+
+// startToken marks the beginning of the next input token.
+// It must be followed by a call to endToken, once the token's text has
+// been consumed using readRune.
+func (in *input) startToken() {
+	in.tokenStart = in.remaining
+	in.token.text = ""
+	in.token.pos = in.pos
+}
+
+// endToken marks the end of an input token.
+// It records the actual token string in tok.text.
+// A single trailing newline (LF or CRLF) will be removed from comment tokens.
+func (in *input) endToken(kind tokenKind) {
+	in.token.kind = kind
+	text := string(in.tokenStart[:len(in.tokenStart)-len(in.remaining)])
+	if kind.isComment() {
+		if strings.HasSuffix(text, "\r\n") {
+			text = text[:len(text)-2]
+		} else {
+			text = strings.TrimSuffix(text, "\n")
+		}
+	}
+	in.token.text = text
+	in.token.endPos = in.pos
+}
+
+// peek returns the kind of the next token returned by lex.
+func (in *input) peek() tokenKind {
+	return in.token.kind
+}
+
+// lex is called from the parser to obtain the next input token.
+func (in *input) lex() token {
+	tok := in.token
+	in.readToken()
+	return tok
+}
+
+// readToken lexes the next token from the text and stores it in in.token.
+func (in *input) readToken() {
+	// Skip past spaces, stopping at non-space or EOF.
+	for !in.eof() {
+		c := in.peekRune()
+		if c == ' ' || c == '\t' || c == '\r' {
+			in.readRune()
+			continue
+		}
+
+		// Comment runs to end of line.
+		if in.peekPrefix("//") {
+			in.startToken()
+
+			// Is this comment the only thing on its line?
+			// Find the last \n before this // and see if it's all
+			// spaces from there to here.
+			i := bytes.LastIndex(in.complete[:in.pos.Byte], []byte("\n"))
+			suffix := len(bytes.TrimSpace(in.complete[i+1:in.pos.Byte])) > 0
+			in.readRune()
+			in.readRune()
+
+			// Consume comment.
+			for len(in.remaining) > 0 && in.readRune() != '\n' {
+			}
+
+			// If we are at top level (not in a statement), hand the comment to
+			// the parser as a _COMMENT token. The grammar is written
+			// to handle top-level comments itself.
+			if !suffix {
+				in.endToken(_COMMENT)
+				return
+			}
+
+			// Otherwise, save comment for later attachment to syntax tree.
+			in.endToken(_EOLCOMMENT)
+			in.comments = append(in.comments, Comment{in.token.pos, in.token.text, suffix})
+			return
+		}
+
+		if in.peekPrefix("/*") {
+			in.Error("mod files must use // comments (not /* */ comments)")
+		}
+
+		// Found non-space non-comment.
+		break
+	}
+
+	// Found the beginning of the next token.
+	in.startToken()
+
+	// End of file.
+	if in.eof() {
+		in.endToken(_EOF)
+		return
+	}
+
+	// Punctuation tokens.
+	switch c := in.peekRune(); c {
+	case '\n', '(', ')', '[', ']', '{', '}', ',':
+		in.readRune()
+		in.endToken(tokenKind(c))
+		return
+
+	case '"', '`': // quoted string
+		quote := c
+		in.readRune()
+		for {
+			if in.eof() {
+				in.pos = in.token.pos
+				in.Error("unexpected EOF in string")
+			}
+			if in.peekRune() == '\n' {
+				in.Error("unexpected newline in string")
+			}
+			c := in.readRune()
+			if c == quote {
+				break
+			}
+			if c == '\\' && quote != '`' {
+				if in.eof() {
+					in.pos = in.token.pos
+					in.Error("unexpected EOF in string")
+				}
+				in.readRune()
+			}
+		}
+		in.endToken(_STRING)
+		return
+	}
+
+	// Checked all punctuation. Must be identifier token.
+	if c := in.peekRune(); !isIdent(c) {
+		in.Error(fmt.Sprintf("unexpected input character %#q", c))
+	}
+
+	// Scan over identifier.
+	for isIdent(in.peekRune()) {
+		if in.peekPrefix("//") {
+			break
+		}
+		if in.peekPrefix("/*") {
+			in.Error("mod files must use // comments (not /* */ comments)")
+		}
+		in.readRune()
+	}
+	in.endToken(_IDENT)
+}
+
+// isIdent reports whether c is an identifier rune.
+// We treat most printable runes as identifier runes, except for a handful of
+// ASCII punctuation characters.
+func isIdent(c int) bool {
+	switch r := rune(c); r {
+	case ' ', '(', ')', '[', ']', '{', '}', ',':
+		return false
+	default:
+		return !unicode.IsSpace(r) && unicode.IsPrint(r)
+	}
+}
+
+// Comment assignment.
+// We build two lists of all subexpressions, preorder and postorder.
+// The preorder list is ordered by start location, with outer expressions first.
+// The postorder list is ordered by end location, with outer expressions last.
+// We use the preorder list to assign each whole-line comment to the syntax
+// immediately following it, and we use the postorder list to assign each
+// end-of-line comment to the syntax immediately preceding it.
+
+// order walks the expression adding it and its subexpressions to the
+// preorder and postorder lists.
+func (in *input) order(x Expr) {
+	if x != nil {
+		in.pre = append(in.pre, x)
+	}
+	switch x := x.(type) {
+	default:
+		panic(fmt.Errorf("order: unexpected type %T", x))
+	case nil:
+		// nothing
+	case *LParen, *RParen:
+		// nothing
+	case *CommentBlock:
+		// nothing
+	case *Line:
+		// nothing
+	case *FileSyntax:
+		for _, stmt := range x.Stmt {
+			in.order(stmt)
+		}
+	case *LineBlock:
+		in.order(&x.LParen)
+		for _, l := range x.Line {
+			in.order(l)
+		}
+		in.order(&x.RParen)
+	}
+	if x != nil {
+		in.post = append(in.post, x)
+	}
+}
+
+// assignComments attaches comments to nearby syntax.
+func (in *input) assignComments() {
+	const debug = false
+
+	// Generate preorder and postorder lists.
+	in.order(in.file)
+
+	// Split into whole-line comments and suffix comments.
+	var line, suffix []Comment
+	for _, com := range in.comments {
+		if com.Suffix {
+			suffix = append(suffix, com)
+		} else {
+			line = append(line, com)
+		}
+	}
+
+	if debug {
+		for _, c := range line {
+			fmt.Fprintf(os.Stderr, "LINE %q :%d:%d #%d\n", c.Token, c.Start.Line, c.Start.LineRune, c.Start.Byte)
+		}
+	}
+
+	// Assign line comments to syntax immediately following.
+	for _, x := range in.pre {
+		start, _ := x.Span()
+		if debug {
+			fmt.Fprintf(os.Stderr, "pre %T :%d:%d #%d\n", x, start.Line, start.LineRune, start.Byte)
+		}
+		xcom := x.Comment()
+		for len(line) > 0 && start.Byte >= line[0].Start.Byte {
+			if debug {
+				fmt.Fprintf(os.Stderr, "ASSIGN LINE %q #%d\n", line[0].Token, line[0].Start.Byte)
+			}
+			xcom.Before = append(xcom.Before, line[0])
+			line = line[1:]
+		}
+	}
+
+	// Remaining line comments go at end of file.
+	in.file.After = append(in.file.After, line...)
+
+	if debug {
+		for _, c := range suffix {
+			fmt.Fprintf(os.Stderr, "SUFFIX %q :%d:%d #%d\n", c.Token, c.Start.Line, c.Start.LineRune, c.Start.Byte)
+		}
+	}
+
+	// Assign suffix comments to syntax immediately before.
+	for i := len(in.post) - 1; i >= 0; i-- {
+		x := in.post[i]
+
+		start, end := x.Span()
+		if debug {
+			fmt.Fprintf(os.Stderr, "post %T :%d:%d #%d :%d:%d #%d\n", x, start.Line, start.LineRune, start.Byte, end.Line, end.LineRune, end.Byte)
+		}
+
+		// Do not assign suffix comments to end of line block or whole file.
+		// Instead assign them to the last element inside.
+		switch x.(type) {
+		case *FileSyntax:
+			continue
+		}
+
+		// Do not assign suffix comments to something that starts
+		// on an earlier line, so that in
+		//
+		//	x ( y
+		//		z ) // comment
+		//
+		// we assign the comment to z and not to x ( ... ).
+		if start.Line != end.Line {
+			continue
+		}
+		xcom := x.Comment()
+		for len(suffix) > 0 && end.Byte <= suffix[len(suffix)-1].Start.Byte {
+			if debug {
+				fmt.Fprintf(os.Stderr, "ASSIGN SUFFIX %q #%d\n", suffix[len(suffix)-1].Token, suffix[len(suffix)-1].Start.Byte)
+			}
+			xcom.Suffix = append(xcom.Suffix, suffix[len(suffix)-1])
+			suffix = suffix[:len(suffix)-1]
+		}
+	}
+
+	// We assigned suffix comments in reverse.
+	// If multiple suffix comments were appended to the same
+	// expression node, they are now in reverse. Fix that.
+	for _, x := range in.post {
+		reverseComments(x.Comment().Suffix)
+	}
+
+	// Remaining suffix comments go at beginning of file.
+	in.file.Before = append(in.file.Before, suffix...)
+}
+
+// reverseComments reverses the []Comment list.
+func reverseComments(list []Comment) {
+	for i, j := 0, len(list)-1; i < j; i, j = i+1, j-1 {
+		list[i], list[j] = list[j], list[i]
+	}
+}
+
+func (in *input) parseFile() {
+	in.file = new(FileSyntax)
+	var cb *CommentBlock
+	for {
+		switch in.peek() {
+		case '\n':
+			in.lex()
+			if cb != nil {
+				in.file.Stmt = append(in.file.Stmt, cb)
+				cb = nil
+			}
+		case _COMMENT:
+			tok := in.lex()
+			if cb == nil {
+				cb = &CommentBlock{Start: tok.pos}
+			}
+			com := cb.Comment()
+			com.Before = append(com.Before, Comment{Start: tok.pos, Token: tok.text})
+		case _EOF:
+			if cb != nil {
+				in.file.Stmt = append(in.file.Stmt, cb)
+			}
+			return
+		default:
+			in.parseStmt()
+			if cb != nil {
+				in.file.Stmt[len(in.file.Stmt)-1].Comment().Before = cb.Before
+				cb = nil
+			}
+		}
+	}
+}
+
+func (in *input) parseStmt() {
+	tok := in.lex()
+	start := tok.pos
+	end := tok.endPos
+	tokens := []string{tok.text}
+	for {
+		tok := in.lex()
+		switch {
+		case tok.kind.isEOL():
+			in.file.Stmt = append(in.file.Stmt, &Line{
+				Start: start,
+				Token: tokens,
+				End:   end,
+			})
+			return
+
+		case tok.kind == '(':
+			if next := in.peek(); next.isEOL() {
+				// Start of block: no more tokens on this line.
+				in.file.Stmt = append(in.file.Stmt, in.parseLineBlock(start, tokens, tok))
+				return
+			} else if next == ')' {
+				rparen := in.lex()
+				if in.peek().isEOL() {
+					// Empty block.
+					in.lex()
+					in.file.Stmt = append(in.file.Stmt, &LineBlock{
+						Start:  start,
+						Token:  tokens,
+						LParen: LParen{Pos: tok.pos},
+						RParen: RParen{Pos: rparen.pos},
+					})
+					return
+				}
+				// '( )' in the middle of the line, not a block.
+				tokens = append(tokens, tok.text, rparen.text)
+			} else {
+				// '(' in the middle of the line, not a block.
+				tokens = append(tokens, tok.text)
+			}
+
+		default:
+			tokens = append(tokens, tok.text)
+			end = tok.endPos
+		}
+	}
+}
+
+func (in *input) parseLineBlock(start Position, token []string, lparen token) *LineBlock {
+	x := &LineBlock{
+		Start:  start,
+		Token:  token,
+		LParen: LParen{Pos: lparen.pos},
+	}
+	var comments []Comment
+	for {
+		switch in.peek() {
+		case _EOLCOMMENT:
+			// Suffix comment, will be attached later by assignComments.
+			in.lex()
+		case '\n':
+			// Blank line. Add an empty comment to preserve it.
+			in.lex()
+			if len(comments) == 0 && len(x.Line) > 0 || len(comments) > 0 && comments[len(comments)-1].Token != "" {
+				comments = append(comments, Comment{})
+			}
+		case _COMMENT:
+			tok := in.lex()
+			comments = append(comments, Comment{Start: tok.pos, Token: tok.text})
+		case _EOF:
+			in.Error(fmt.Sprintf("syntax error (unterminated block started at %s:%d:%d)", in.filename, x.Start.Line, x.Start.LineRune))
+		case ')':
+			rparen := in.lex()
+			x.RParen.Before = comments
+			x.RParen.Pos = rparen.pos
+			if !in.peek().isEOL() {
+				in.Error("syntax error (expected newline after closing paren)")
+			}
+			in.lex()
+			return x
+		default:
+			l := in.parseLine()
+			x.Line = append(x.Line, l)
+			l.Comment().Before = comments
+			comments = nil
+		}
+	}
+}
+
+func (in *input) parseLine() *Line {
+	tok := in.lex()
+	if tok.kind.isEOL() {
+		in.Error("internal parse error: parseLine at end of line")
+	}
+	start := tok.pos
+	end := tok.endPos
+	tokens := []string{tok.text}
+	for {
+		tok := in.lex()
+		if tok.kind.isEOL() {
+			return &Line{
+				Start:   start,
+				Token:   tokens,
+				End:     end,
+				InBlock: true,
+			}
+		}
+		tokens = append(tokens, tok.text)
+		end = tok.endPos
+	}
+}
+
+var (
+	slashSlash = []byte("//")
+	moduleStr  = []byte("module")
+)
+
+// ModulePath returns the module path from the gomod file text.
+// If it cannot find a module path, it returns an empty string.
+// It is tolerant of unrelated problems in the go.mod file.
+func ModulePath(mod []byte) string {
+	for len(mod) > 0 {
+		line := mod
+		mod = nil
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, mod = line[:i], line[i+1:]
+		}
+		if i := bytes.Index(line, slashSlash); i >= 0 {
+			line = line[:i]
+		}
+		line = bytes.TrimSpace(line)
+		if !bytes.HasPrefix(line, moduleStr) {
+			continue
+		}
+		line = line[len(moduleStr):]
+		n := len(line)
+		line = bytes.TrimSpace(line)
+		if len(line) == n || len(line) == 0 {
+			continue
+		}
+
+		if line[0] == '"' || line[0] == '`' {
+			p, err := strconv.Unquote(string(line))
+			if err != nil {
+				return "" // malformed quoted string or multiline module path
+			}
+			return p
+		}
+
+		return string(line)
+	}
+	return "" // missing module path
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/read_test.go

@@ -0,0 +1,605 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package modfile
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// exists reports whether the named file exists.
+func exists(name string) bool {
+	_, err := os.Stat(name)
+	return err == nil
+}
+
+// Test that reading and then writing the golden files
+// does not change their output.
+func TestPrintGolden(t *testing.T) {
+	outs, err := filepath.Glob("testdata/*.golden")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, out := range outs {
+		out := out
+		name := strings.TrimSuffix(filepath.Base(out), ".golden")
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			testPrint(t, out, out)
+		})
+	}
+}
+
+// testPrint is a helper for testing the printer.
+// It reads the file named in, reformats it, and compares
+// the result to the file named out.
+func testPrint(t *testing.T, in, out string) {
+	data, err := os.ReadFile(in)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	golden, err := os.ReadFile(out)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	base := "testdata/" + filepath.Base(in)
+	f, err := parse(in, data)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	ndata := Format(f)
+
+	if !bytes.Equal(ndata, golden) {
+		t.Errorf("formatted %s incorrectly: diff shows -golden, +ours", base)
+		tdiff(t, string(golden), string(ndata))
+		return
+	}
+}
+
+// TestParsePunctuation verifies that certain ASCII punctuation characters
+// (brackets, commas) are lexed as separate tokens, even when they're
+// surrounded by identifier characters.
+func TestParsePunctuation(t *testing.T) {
+	for _, test := range []struct {
+		desc, src, want string
+	}{
+		{"paren", "require ()", "require ( )"},
+		{"brackets", "require []{},", "require [ ] { } ,"},
+		{"mix", "require a[b]c{d}e,", "require a [ b ] c { d } e ,"},
+		{"block_mix", "require (\n\ta[b]\n)", "require ( a [ b ] )"},
+		{"interval", "require [v1.0.0, v1.1.0)", "require [ v1.0.0 , v1.1.0 )"},
+	} {
+		t.Run(test.desc, func(t *testing.T) {
+			f, err := parse("go.mod", []byte(test.src))
+			if err != nil {
+				t.Fatalf("parsing %q: %v", test.src, err)
+			}
+			var tokens []string
+			for _, stmt := range f.Stmt {
+				switch stmt := stmt.(type) {
+				case *Line:
+					tokens = append(tokens, stmt.Token...)
+				case *LineBlock:
+					tokens = append(tokens, stmt.Token...)
+					tokens = append(tokens, "(")
+					for _, line := range stmt.Line {
+						tokens = append(tokens, line.Token...)
+					}
+					tokens = append(tokens, ")")
+				default:
+					t.Fatalf("parsing %q: unexpected statement of type %T", test.src, stmt)
+				}
+			}
+			got := strings.Join(tokens, " ")
+			if got != test.want {
+				t.Errorf("parsing %q: got %q, want %q", test.src, got, test.want)
+			}
+		})
+	}
+}
+
+func TestParseLax(t *testing.T) {
+	badFile := []byte(`module m
+		surprise attack
+		x y (
+			z
+		)
+		exclude v1.2.3
+		replace <-!!!
+		retract v1.2.3 v1.2.4
+		retract (v1.2.3, v1.2.4]
+		retract v1.2.3 (
+			key1 value1
+			key2 value2
+		)
+		require good v1.0.0
+	`)
+	f, err := ParseLax("file", badFile, nil)
+	if err != nil {
+		t.Fatalf("ParseLax did not ignore irrelevant errors: %v", err)
+	}
+	if f.Module == nil || f.Module.Mod.Path != "m" {
+		t.Errorf("module directive was not parsed")
+	}
+	if len(f.Require) != 1 || f.Require[0].Mod.Path != "good" {
+		t.Errorf("require directive at end of file was not parsed")
+	}
+}
+
+// Test that when files in the testdata directory are parsed
+// and printed and parsed again, we get the same parse tree
+// both times.
+func TestPrintParse(t *testing.T) {
+	outs, err := filepath.Glob("testdata/*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, out := range outs {
+		out := out
+		name := filepath.Base(out)
+		if !strings.HasSuffix(out, ".in") && !strings.HasSuffix(out, ".golden") {
+			continue
+		}
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			data, err := os.ReadFile(out)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			base := "testdata/" + filepath.Base(out)
+			f, err := parse(base, data)
+			if err != nil {
+				t.Fatalf("parsing original: %v", err)
+			}
+
+			ndata := Format(f)
+			f2, err := parse(base, ndata)
+			if err != nil {
+				t.Fatalf("parsing reformatted: %v", err)
+			}
+
+			eq := eqchecker{file: base}
+			if err := eq.check(f, f2); err != nil {
+				t.Errorf("not equal (parse/Format/parse): %v", err)
+			}
+
+			pf1, err := Parse(base, data, nil)
+			if err != nil {
+				switch base {
+				case "testdata/block.golden",
+					"testdata/block.in",
+					"testdata/comment.golden",
+					"testdata/comment.in",
+					"testdata/rule1.golden":
+					// ignore
+				default:
+					t.Errorf("should parse %v: %v", base, err)
+				}
+			}
+			if err == nil {
+				pf2, err := Parse(base, ndata, nil)
+				if err != nil {
+					t.Fatalf("Parsing reformatted: %v", err)
+				}
+				eq := eqchecker{file: base}
+				if err := eq.check(pf1, pf2); err != nil {
+					t.Errorf("not equal (parse/Format/Parse): %v", err)
+				}
+
+				ndata2, err := pf1.Format()
+				if err != nil {
+					t.Errorf("reformat: %v", err)
+				}
+				pf3, err := Parse(base, ndata2, nil)
+				if err != nil {
+					t.Fatalf("Parsing reformatted2: %v", err)
+				}
+				eq = eqchecker{file: base}
+				if err := eq.check(pf1, pf3); err != nil {
+					t.Errorf("not equal (Parse/Format/Parse): %v", err)
+				}
+				ndata = ndata2
+			}
+
+			if strings.HasSuffix(out, ".in") {
+				golden, err := os.ReadFile(strings.TrimSuffix(out, ".in") + ".golden")
+				if err != nil {
+					t.Fatal(err)
+				}
+				if !bytes.Equal(ndata, golden) {
+					t.Errorf("formatted %s incorrectly: diff shows -golden, +ours", base)
+					tdiff(t, string(golden), string(ndata))
+					return
+				}
+			}
+		})
+	}
+}
+
+// An eqchecker holds state for checking the equality of two parse trees.
+type eqchecker struct {
+	file string
+	pos  Position
+}
+
+// errorf returns an error described by the printf-style format and arguments,
+// inserting the current file position before the error text.
+func (eq *eqchecker) errorf(format string, args ...interface{}) error {
+	return fmt.Errorf("%s:%d: %s", eq.file, eq.pos.Line,
+		fmt.Sprintf(format, args...))
+}
+
+// check checks that v and w represent the same parse tree.
+// If not, it returns an error describing the first difference.
+func (eq *eqchecker) check(v, w interface{}) error {
+	return eq.checkValue(reflect.ValueOf(v), reflect.ValueOf(w))
+}
+
+var (
+	posType      = reflect.TypeOf(Position{})
+	commentsType = reflect.TypeOf(Comments{})
+)
+
+// checkValue checks that v and w represent the same parse tree.
+// If not, it returns an error describing the first difference.
+func (eq *eqchecker) checkValue(v, w reflect.Value) error {
+	// inner returns the innermost expression for v.
+	// if v is a non-nil interface value, it returns the concrete
+	// value in the interface.
+	inner := func(v reflect.Value) reflect.Value {
+		for {
+			if v.Kind() == reflect.Interface && !v.IsNil() {
+				v = v.Elem()
+				continue
+			}
+			break
+		}
+		return v
+	}
+
+	v = inner(v)
+	w = inner(w)
+	if v.Kind() == reflect.Invalid && w.Kind() == reflect.Invalid {
+		return nil
+	}
+	if v.Kind() == reflect.Invalid {
+		return eq.errorf("nil interface became %s", w.Type())
+	}
+	if w.Kind() == reflect.Invalid {
+		return eq.errorf("%s became nil interface", v.Type())
+	}
+
+	if v.Type() != w.Type() {
+		return eq.errorf("%s became %s", v.Type(), w.Type())
+	}
+
+	if p, ok := v.Interface().(Expr); ok {
+		eq.pos, _ = p.Span()
+	}
+
+	switch v.Kind() {
+	default:
+		return eq.errorf("unexpected type %s", v.Type())
+
+	case reflect.Bool, reflect.Int, reflect.String:
+		vi := v.Interface()
+		wi := w.Interface()
+		if vi != wi {
+			return eq.errorf("%v became %v", vi, wi)
+		}
+
+	case reflect.Slice:
+		vl := v.Len()
+		wl := w.Len()
+		for i := 0; i < vl || i < wl; i++ {
+			if i >= vl {
+				return eq.errorf("unexpected %s", w.Index(i).Type())
+			}
+			if i >= wl {
+				return eq.errorf("missing %s", v.Index(i).Type())
+			}
+			if err := eq.checkValue(v.Index(i), w.Index(i)); err != nil {
+				return err
+			}
+		}
+
+	case reflect.Struct:
+		// Fields in struct must match.
+		t := v.Type()
+		n := t.NumField()
+		for i := 0; i < n; i++ {
+			tf := t.Field(i)
+			switch {
+			default:
+				if err := eq.checkValue(v.Field(i), w.Field(i)); err != nil {
+					return err
+				}
+
+			case tf.Type == posType: // ignore positions
+			case tf.Type == commentsType: // ignore comment assignment
+			}
+		}
+
+	case reflect.Ptr, reflect.Interface:
+		if v.IsNil() != w.IsNil() {
+			if v.IsNil() {
+				return eq.errorf("unexpected %s", w.Elem().Type())
+			}
+			return eq.errorf("missing %s", v.Elem().Type())
+		}
+		if err := eq.checkValue(v.Elem(), w.Elem()); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// diff returns the output of running diff on b1 and b2.
+func diff(b1, b2 []byte) (data []byte, err error) {
+	f1, err := os.CreateTemp("", "testdiff")
+	if err != nil {
+		return nil, err
+	}
+	defer os.Remove(f1.Name())
+	defer f1.Close()
+
+	f2, err := os.CreateTemp("", "testdiff")
+	if err != nil {
+		return nil, err
+	}
+	defer os.Remove(f2.Name())
+	defer f2.Close()
+
+	f1.Write(b1)
+	f2.Write(b2)
+
+	data, err = exec.Command("diff", "-u", f1.Name(), f2.Name()).CombinedOutput()
+	if len(data) > 0 {
+		// diff exits with a non-zero status when the files don't match.
+		// Ignore that failure as long as we get output.
+		err = nil
+	}
+	return
+}
+
+// tdiff logs the diff output to t.Error.
+func tdiff(t *testing.T, a, b string) {
+	data, err := diff([]byte(a), []byte(b))
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	t.Error(string(data))
+}
+
+var modulePathTests = []struct {
+	input    []byte
+	expected string
+}{
+	{input: []byte("module \"github.com/rsc/vgotest\""), expected: "github.com/rsc/vgotest"},
+	{input: []byte("module github.com/rsc/vgotest"), expected: "github.com/rsc/vgotest"},
+	{input: []byte("module  \"github.com/rsc/vgotest\""), expected: "github.com/rsc/vgotest"},
+	{input: []byte("module  github.com/rsc/vgotest"), expected: "github.com/rsc/vgotest"},
+	{input: []byte("module `github.com/rsc/vgotest`"), expected: "github.com/rsc/vgotest"},
+	{input: []byte("module \"github.com/rsc/vgotest/v2\""), expected: "github.com/rsc/vgotest/v2"},
+	{input: []byte("module github.com/rsc/vgotest/v2"), expected: "github.com/rsc/vgotest/v2"},
+	{input: []byte("module \"gopkg.in/yaml.v2\""), expected: "gopkg.in/yaml.v2"},
+	{input: []byte("module gopkg.in/yaml.v2"), expected: "gopkg.in/yaml.v2"},
+	{input: []byte("module \"gopkg.in/check.v1\"\n"), expected: "gopkg.in/check.v1"},
+	{input: []byte("module \"gopkg.in/check.v1\n\""), expected: ""},
+	{input: []byte("module gopkg.in/check.v1\n"), expected: "gopkg.in/check.v1"},
+	{input: []byte("module \"gopkg.in/check.v1\"\r\n"), expected: "gopkg.in/check.v1"},
+	{input: []byte("module gopkg.in/check.v1\r\n"), expected: "gopkg.in/check.v1"},
+	{input: []byte("module \"gopkg.in/check.v1\"\n\n"), expected: "gopkg.in/check.v1"},
+	{input: []byte("module gopkg.in/check.v1\n\n"), expected: "gopkg.in/check.v1"},
+	{input: []byte("module \n\"gopkg.in/check.v1\"\n\n"), expected: ""},
+	{input: []byte("module \ngopkg.in/check.v1\n\n"), expected: ""},
+	{input: []byte("module \"gopkg.in/check.v1\"asd"), expected: ""},
+	{input: []byte("module \n\"gopkg.in/check.v1\"\n\n"), expected: ""},
+	{input: []byte("module \ngopkg.in/check.v1\n\n"), expected: ""},
+	{input: []byte("module \"gopkg.in/check.v1\"asd"), expected: ""},
+	{input: []byte("module  \nmodule a/b/c "), expected: "a/b/c"},
+	{input: []byte("module \"   \""), expected: "   "},
+	{input: []byte("module   "), expected: ""},
+	{input: []byte("module \"  a/b/c  \""), expected: "  a/b/c  "},
+	{input: []byte("module \"github.com/rsc/vgotest1\" // with a comment"), expected: "github.com/rsc/vgotest1"},
+}
+
+func TestModulePath(t *testing.T) {
+	for _, test := range modulePathTests {
+		t.Run(string(test.input), func(t *testing.T) {
+			result := ModulePath(test.input)
+			if result != test.expected {
+				t.Fatalf("ModulePath(%q): %s, want %s", string(test.input), result, test.expected)
+			}
+		})
+	}
+}
+
+func TestParseVersions(t *testing.T) {
+	tests := []struct {
+		desc, input string
+		ok          bool
+		laxOK       bool // ok=true implies laxOK=true; only set if ok=false
+	}{
+		// go lines
+		{desc: "empty", input: "module m\ngo \n", ok: false},
+		{desc: "one", input: "module m\ngo 1\n", ok: false},
+		{desc: "two", input: "module m\ngo 1.22\n", ok: true},
+		{desc: "three", input: "module m\ngo 1.22.333", ok: true},
+		{desc: "before", input: "module m\ngo v1.2\n", ok: false},
+		{desc: "after", input: "module m\ngo 1.2rc1\n", ok: true},
+		{desc: "space", input: "module m\ngo 1.2 3.4\n", ok: false},
+		{desc: "alt1", input: "module m\ngo 1.2.3\n", ok: true},
+		{desc: "alt2", input: "module m\ngo 1.2rc1\n", ok: true},
+		{desc: "alt3", input: "module m\ngo 1.2beta1\n", ok: true},
+		{desc: "alt4", input: "module m\ngo 1.2.beta1\n", ok: false, laxOK: true},
+		{desc: "alt1", input: "module m\ngo v1.2.3\n", ok: false, laxOK: true},
+		{desc: "alt2", input: "module m\ngo v1.2rc1\n", ok: false, laxOK: true},
+		{desc: "alt3", input: "module m\ngo v1.2beta1\n", ok: false, laxOK: true},
+		{desc: "alt4", input: "module m\ngo v1.2.beta1\n", ok: false, laxOK: true},
+		{desc: "alt1", input: "module m\ngo v1.2\n", ok: false, laxOK: true},
+
+		// toolchain lines
+		{desc: "tool", input: "module m\ntoolchain go1.2\n", ok: true},
+		{desc: "tool1", input: "module m\ntoolchain go1.2.3\n", ok: true},
+		{desc: "tool2", input: "module m\ntoolchain go1.2rc1\n", ok: true},
+		{desc: "tool3", input: "module m\ntoolchain go1.2rc1-gccgo\n", ok: true},
+		{desc: "tool4", input: "module m\ntoolchain default\n", ok: true},
+		{desc: "tool5", input: "module m\ntoolchain inconceivable!\n", ok: false, laxOK: true},
+	}
+	t.Run("Strict", func(t *testing.T) {
+		for _, test := range tests {
+			t.Run(test.desc, func(t *testing.T) {
+				if _, err := Parse("go.mod", []byte(test.input), nil); err == nil && !test.ok {
+					t.Error("unexpected success")
+				} else if err != nil && test.ok {
+					t.Errorf("unexpected error: %v", err)
+				}
+			})
+		}
+	})
+	t.Run("Lax", func(t *testing.T) {
+		for _, test := range tests {
+			t.Run(test.desc, func(t *testing.T) {
+				if _, err := ParseLax("go.mod", []byte(test.input), nil); err == nil && !(test.ok || test.laxOK) {
+					t.Error("unexpected success")
+				} else if err != nil && test.ok {
+					t.Errorf("unexpected error: %v", err)
+				}
+			})
+		}
+	})
+}
+
+func TestComments(t *testing.T) {
+	for _, test := range []struct {
+		desc, input, want string
+	}{
+		{
+			desc: "comment_only",
+			input: `
+// a
+// b
+`,
+			want: `
+comments before "// a"
+comments before "// b"
+`,
+		}, {
+			desc: "line",
+			input: `
+// a
+
+// b
+module m // c
+// d
+
+// e
+`,
+			want: `
+comments before "// a"
+line before "// b"
+line suffix "// c"
+comments before "// d"
+comments before "// e"
+`,
+		}, {
+			desc: "block",
+			input: `
+// a
+
+// b
+block ( // c
+	// d
+
+	// e
+	x // f
+	// g
+
+	// h
+) // i
+// j
+
+// k
+`,
+			want: `
+comments before "// a"
+block before "// b"
+lparen suffix "// c"
+blockline before "// d"
+blockline before ""
+blockline before "// e"
+blockline suffix "// f"
+rparen before "// g"
+rparen before ""
+rparen before "// h"
+rparen suffix "// i"
+comments before "// j"
+comments before "// k"
+`,
+		}, {
+			desc:  "cr_removed",
+			input: "// a\r\r\n",
+			want:  `comments before "// a\r"`,
+		},
+	} {
+		t.Run(test.desc, func(t *testing.T) {
+			f, err := ParseLax("go.mod", []byte(test.input), nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			buf := &bytes.Buffer{}
+			printComments := func(prefix string, cs *Comments) {
+				for _, c := range cs.Before {
+					fmt.Fprintf(buf, "%s before %q\n", prefix, c.Token)
+				}
+				for _, c := range cs.Suffix {
+					fmt.Fprintf(buf, "%s suffix %q\n", prefix, c.Token)
+				}
+				for _, c := range cs.After {
+					fmt.Fprintf(buf, "%s after %q\n", prefix, c.Token)
+				}
+			}
+
+			printComments("file", &f.Syntax.Comments)
+			for _, stmt := range f.Syntax.Stmt {
+				switch stmt := stmt.(type) {
+				case *CommentBlock:
+					printComments("comments", stmt.Comment())
+				case *Line:
+					printComments("line", stmt.Comment())
+				case *LineBlock:
+					printComments("block", stmt.Comment())
+					printComments("lparen", stmt.LParen.Comment())
+					for _, line := range stmt.Line {
+						printComments("blockline", line.Comment())
+					}
+					printComments("rparen", stmt.RParen.Comment())
+				}
+			}
+
+			got := strings.TrimSpace(buf.String())
+			want := strings.TrimSpace(test.want)
+			if got != want {
+				t.Errorf("got:\n%s\nwant:\n%s", got, want)
+			}
+		})
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/block.golden

@@ -0,0 +1,36 @@
+// comment
+x "y" z
+
+// block
+block ( // block-eol
+	// x-before-line
+
+	"x" (y // x-eol
+	"x") y // y-eol
+	"x1"
+	"x2"
+	// line
+	"x3"
+	"x4"
+
+	"x5"
+
+	// y-line
+	"y" //  y-eol
+
+	"z" // z-eol
+) // block-eol2
+
+block1 (
+)
+
+block2 (x y z)
+
+block3 "w" (
+) // empty block
+
+block4 "x" () "y" // not a block
+
+block5 ("z" // also not a block
+
+// eof

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/block.in

@@ -0,0 +1,33 @@
+// comment
+x "y" z
+
+// block
+block ( // block-eol
+	// x-before-line
+	
+	"x" ( y // x-eol
+	"x" ) y // y-eol
+	"x1"
+	"x2"
+	// line
+	"x3"
+	"x4"
+	
+	"x5"
+	
+	// y-line
+	"y" //  y-eol
+	
+	"z" // z-eol
+) // block-eol2
+
+
+block1()
+
+block2 (x y z)
+
+block3 "w" ( ) // empty block
+block4 "x" ( ) "y" // not a block
+block5 ( "z" // also not a block
+
+// eof

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/comment.golden

@@ -0,0 +1,10 @@
+// comment
+module "x" // eol
+
+// mid comment
+
+// comment 2
+// comment 2 line 2
+module "y" // eoy
+
+// comment 3

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/comment.in

@@ -0,0 +1,8 @@
+// comment
+module "x" // eol
+// mid comment
+
+// comment 2
+// comment 2 line 2
+module "y" // eoy
+// comment 3

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/goline.golden

@@ -0,0 +1,3 @@
+go 1.2.3
+
+toolchain default

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/goline.in

@@ -0,0 +1,2 @@
+go 1.2.3
+toolchain default

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/gopkg.in.golden

@@ -0,0 +1,6 @@
+module x
+
+require (
+	gopkg.in/mgo.v2 v2.0.0-20160818020120-3f83fa500528
+	gopkg.in/yaml.v2 v2.2.1
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/module.golden

@@ -0,0 +1 @@
+module abc

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/module.in

@@ -0,0 +1 @@
+module "abc"

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/replace.golden

@@ -0,0 +1,12 @@
+module abc
+
+replace xyz v1.2.3 => /tmp/z
+
+replace xyz v1.3.4 => my/xyz v1.3.4-me
+
+replace (
+	w v1.0.0 => "./a,"
+	w v1.0.1 => "./a()"
+	w v1.0.2 => "./a[]"
+	w v1.0.3 => "./a{}"
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/replace.in

@@ -0,0 +1,12 @@
+module "abc"
+
+replace "xyz" v1.2.3 => "/tmp/z"
+
+replace "xyz" v1.3.4 => "my/xyz" v1.3.4-me
+
+replace (
+	"w" v1.0.0 => "./a,"
+	"w" v1.0.1 => "./a()"
+	"w" v1.0.2 => "./a[]"
+	"w" v1.0.3 => "./a{}"
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/replace2.golden

@@ -0,0 +1,10 @@
+module abc
+
+replace (
+	xyz v1.2.3 => /tmp/z
+	xyz v1.3.4 => my/xyz v1.3.4-me
+	xyz v1.4.5 => "/tmp/my dir"
+	xyz v1.5.6 => my/xyz v1.5.6
+
+	xyz => my/other/xyz v1.5.4
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/replace2.in

@@ -0,0 +1,10 @@
+module "abc"
+
+replace (
+	"xyz" v1.2.3 => "/tmp/z"
+	"xyz" v1.3.4 => "my/xyz" "v1.3.4-me"
+	xyz "v1.4.5" => "/tmp/my dir"
+	xyz v1.5.6 => my/xyz v1.5.6
+
+	xyz => my/other/xyz v1.5.4
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/retract.golden

@@ -0,0 +1,11 @@
+module abc
+
+retract v1.2.3
+
+retract [v1.2.3, v1.2.4]
+
+retract (
+	v1.2.3
+
+	[v1.2.3, v1.2.4]
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/retract.in

@@ -0,0 +1,11 @@
+module abc
+
+retract "v1.2.3"
+
+retract [ "v1.2.3" , "v1.2.4" ]
+
+retract (
+	"v1.2.3"
+
+	[ "v1.2.3" , "v1.2.4" ]
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/rule1.golden

@@ -0,0 +1,7 @@
+module "x"
+
+module "y"
+
+require "x"
+
+require x

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/comment.golden

@@ -0,0 +1,10 @@
+// comment
+use x // eol
+
+// mid comment
+
+// comment 2
+// comment 2 line 2
+use y // eoy
+
+// comment 3

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/comment.in

@@ -0,0 +1,8 @@
+// comment
+use "x" // eol
+// mid comment
+
+// comment 2
+// comment 2 line 2
+use "y" // eoy
+// comment 3

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/goline.golden

@@ -0,0 +1,3 @@
+go 1.2.3
+
+toolchain default

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/goline.in

@@ -0,0 +1,2 @@
+go 1.2.3
+toolchain default

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/replace.golden

@@ -0,0 +1,12 @@
+use abc
+
+replace xyz v1.2.3 => /tmp/z
+
+replace xyz v1.3.4 => my/xyz v1.3.4-me
+
+replace (
+	w v1.0.0 => "./a,"
+	w v1.0.1 => "./a()"
+	w v1.0.2 => "./a[]"
+	w v1.0.3 => "./a{}"
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/replace.in

@@ -0,0 +1,12 @@
+use "abc"
+
+replace "xyz" v1.2.3 => "/tmp/z"
+
+replace "xyz" v1.3.4 => "my/xyz" v1.3.4-me
+
+replace (
+	"w" v1.0.0 => "./a,"
+	"w" v1.0.1 => "./a()"
+	"w" v1.0.2 => "./a[]"
+	"w" v1.0.3 => "./a{}"
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/replace2.golden

@@ -0,0 +1,10 @@
+use abc
+
+replace (
+	xyz v1.2.3 => /tmp/z
+	xyz v1.3.4 => my/xyz v1.3.4-me
+	xyz v1.4.5 => "/tmp/my dir"
+	xyz v1.5.6 => my/xyz v1.5.6
+
+	xyz => my/other/xyz v1.5.4
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/replace2.in

@@ -0,0 +1,10 @@
+use "abc"
+
+replace (
+	"xyz" v1.2.3 => "/tmp/z"
+	"xyz" v1.3.4 => "my/xyz" "v1.3.4-me"
+	xyz "v1.4.5" => "/tmp/my dir"
+	xyz v1.5.6 => my/xyz v1.5.6
+
+	xyz => my/other/xyz v1.5.4
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/use.golden

@@ -0,0 +1,7 @@
+use ../foo
+
+use (
+	/bar
+
+	baz
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/testdata/work/use.in

@@ -0,0 +1,7 @@
+use "../foo"
+
+use (
+	"/bar"
+
+	"baz"
+)

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/work.go

@@ -0,0 +1,285 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package modfile
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// A WorkFile is the parsed, interpreted form of a go.work file.
+type WorkFile struct {
+	Go        *Go
+	Toolchain *Toolchain
+	Use       []*Use
+	Replace   []*Replace
+
+	Syntax *FileSyntax
+}
+
+// A Use is a single directory statement.
+type Use struct {
+	Path       string // Use path of module.
+	ModulePath string // Module path in the comment.
+	Syntax     *Line
+}
+
+// ParseWork parses and returns a go.work file.
+//
+// file is the name of the file, used in positions and errors.
+//
+// data is the content of the file.
+//
+// fix is an optional function that canonicalizes module versions.
+// If fix is nil, all module versions must be canonical ([module.CanonicalVersion]
+// must return the same string).
+func ParseWork(file string, data []byte, fix VersionFixer) (*WorkFile, error) {
+	fs, err := parse(file, data)
+	if err != nil {
+		return nil, err
+	}
+	f := &WorkFile{
+		Syntax: fs,
+	}
+	var errs ErrorList
+
+	for _, x := range fs.Stmt {
+		switch x := x.(type) {
+		case *Line:
+			f.add(&errs, x, x.Token[0], x.Token[1:], fix)
+
+		case *LineBlock:
+			if len(x.Token) > 1 {
+				errs = append(errs, Error{
+					Filename: file,
+					Pos:      x.Start,
+					Err:      fmt.Errorf("unknown block type: %s", strings.Join(x.Token, " ")),
+				})
+				continue
+			}
+			switch x.Token[0] {
+			default:
+				errs = append(errs, Error{
+					Filename: file,
+					Pos:      x.Start,
+					Err:      fmt.Errorf("unknown block type: %s", strings.Join(x.Token, " ")),
+				})
+				continue
+			case "use", "replace":
+				for _, l := range x.Line {
+					f.add(&errs, l, x.Token[0], l.Token, fix)
+				}
+			}
+		}
+	}
+
+	if len(errs) > 0 {
+		return nil, errs
+	}
+	return f, nil
+}
+
+// Cleanup cleans up the file f after any edit operations.
+// To avoid quadratic behavior, modifications like [WorkFile.DropRequire]
+// clear the entry but do not remove it from the slice.
+// Cleanup cleans out all the cleared entries.
+func (f *WorkFile) Cleanup() {
+	w := 0
+	for _, r := range f.Use {
+		if r.Path != "" {
+			f.Use[w] = r
+			w++
+		}
+	}
+	f.Use = f.Use[:w]
+
+	w = 0
+	for _, r := range f.Replace {
+		if r.Old.Path != "" {
+			f.Replace[w] = r
+			w++
+		}
+	}
+	f.Replace = f.Replace[:w]
+
+	f.Syntax.Cleanup()
+}
+
+func (f *WorkFile) AddGoStmt(version string) error {
+	if !GoVersionRE.MatchString(version) {
+		return fmt.Errorf("invalid language version %q", version)
+	}
+	if f.Go == nil {
+		stmt := &Line{Token: []string{"go", version}}
+		f.Go = &Go{
+			Version: version,
+			Syntax:  stmt,
+		}
+		// Find the first non-comment-only block and add
+		// the go statement before it. That will keep file comments at the top.
+		i := 0
+		for i = 0; i < len(f.Syntax.Stmt); i++ {
+			if _, ok := f.Syntax.Stmt[i].(*CommentBlock); !ok {
+				break
+			}
+		}
+		f.Syntax.Stmt = append(append(f.Syntax.Stmt[:i:i], stmt), f.Syntax.Stmt[i:]...)
+	} else {
+		f.Go.Version = version
+		f.Syntax.updateLine(f.Go.Syntax, "go", version)
+	}
+	return nil
+}
+
+func (f *WorkFile) AddToolchainStmt(name string) error {
+	if !ToolchainRE.MatchString(name) {
+		return fmt.Errorf("invalid toolchain name %q", name)
+	}
+	if f.Toolchain == nil {
+		stmt := &Line{Token: []string{"toolchain", name}}
+		f.Toolchain = &Toolchain{
+			Name:   name,
+			Syntax: stmt,
+		}
+		// Find the go line and add the toolchain line after it.
+		// Or else find the first non-comment-only block and add
+		// the toolchain line before it. That will keep file comments at the top.
+		i := 0
+		for i = 0; i < len(f.Syntax.Stmt); i++ {
+			if line, ok := f.Syntax.Stmt[i].(*Line); ok && len(line.Token) > 0 && line.Token[0] == "go" {
+				i++
+				goto Found
+			}
+		}
+		for i = 0; i < len(f.Syntax.Stmt); i++ {
+			if _, ok := f.Syntax.Stmt[i].(*CommentBlock); !ok {
+				break
+			}
+		}
+	Found:
+		f.Syntax.Stmt = append(append(f.Syntax.Stmt[:i:i], stmt), f.Syntax.Stmt[i:]...)
+	} else {
+		f.Toolchain.Name = name
+		f.Syntax.updateLine(f.Toolchain.Syntax, "toolchain", name)
+	}
+	return nil
+}
+
+// DropGoStmt deletes the go statement from the file.
+func (f *WorkFile) DropGoStmt() {
+	if f.Go != nil {
+		f.Go.Syntax.markRemoved()
+		f.Go = nil
+	}
+}
+
+// DropToolchainStmt deletes the toolchain statement from the file.
+func (f *WorkFile) DropToolchainStmt() {
+	if f.Toolchain != nil {
+		f.Toolchain.Syntax.markRemoved()
+		f.Toolchain = nil
+	}
+}
+
+func (f *WorkFile) AddUse(diskPath, modulePath string) error {
+	need := true
+	for _, d := range f.Use {
+		if d.Path == diskPath {
+			if need {
+				d.ModulePath = modulePath
+				f.Syntax.updateLine(d.Syntax, "use", AutoQuote(diskPath))
+				need = false
+			} else {
+				d.Syntax.markRemoved()
+				*d = Use{}
+			}
+		}
+	}
+
+	if need {
+		f.AddNewUse(diskPath, modulePath)
+	}
+	return nil
+}
+
+func (f *WorkFile) AddNewUse(diskPath, modulePath string) {
+	line := f.Syntax.addLine(nil, "use", AutoQuote(diskPath))
+	f.Use = append(f.Use, &Use{Path: diskPath, ModulePath: modulePath, Syntax: line})
+}
+
+func (f *WorkFile) SetUse(dirs []*Use) {
+	need := make(map[string]string)
+	for _, d := range dirs {
+		need[d.Path] = d.ModulePath
+	}
+
+	for _, d := range f.Use {
+		if modulePath, ok := need[d.Path]; ok {
+			d.ModulePath = modulePath
+		} else {
+			d.Syntax.markRemoved()
+			*d = Use{}
+		}
+	}
+
+	// TODO(#45713): Add module path to comment.
+
+	for diskPath, modulePath := range need {
+		f.AddNewUse(diskPath, modulePath)
+	}
+	f.SortBlocks()
+}
+
+func (f *WorkFile) DropUse(path string) error {
+	for _, d := range f.Use {
+		if d.Path == path {
+			d.Syntax.markRemoved()
+			*d = Use{}
+		}
+	}
+	return nil
+}
+
+func (f *WorkFile) AddReplace(oldPath, oldVers, newPath, newVers string) error {
+	return addReplace(f.Syntax, &f.Replace, oldPath, oldVers, newPath, newVers)
+}
+
+func (f *WorkFile) DropReplace(oldPath, oldVers string) error {
+	for _, r := range f.Replace {
+		if r.Old.Path == oldPath && r.Old.Version == oldVers {
+			r.Syntax.markRemoved()
+			*r = Replace{}
+		}
+	}
+	return nil
+}
+
+func (f *WorkFile) SortBlocks() {
+	f.removeDups() // otherwise sorting is unsafe
+
+	for _, stmt := range f.Syntax.Stmt {
+		block, ok := stmt.(*LineBlock)
+		if !ok {
+			continue
+		}
+		sort.SliceStable(block.Line, func(i, j int) bool {
+			return lineLess(block.Line[i], block.Line[j])
+		})
+	}
+}
+
+// removeDups removes duplicate replace directives.
+//
+// Later replace directives take priority.
+//
+// require directives are not de-duplicated. That's left up to higher-level
+// logic (MVS).
+//
+// retract directives are not de-duplicated since comments are
+// meaningful, and versions may be retracted multiple times.
+func (f *WorkFile) removeDups() {
+	removeDups(f.Syntax, nil, &f.Replace)
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/modfile/work_test.go

@@ -0,0 +1,456 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package modfile
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// TODO(#45713): Update these tests once AddUse sets the module path.
+var workAddUseTests = []struct {
+	desc       string
+	in         string
+	path       string
+	modulePath string
+	out        string
+}{
+	{
+		`empty`,
+		``,
+		`foo`, `bar`,
+		`use foo`,
+	},
+	{
+		`go_stmt_only`,
+		`go 1.17
+		`,
+		`foo`, `bar`,
+		`go 1.17
+		use foo
+		`,
+	},
+	{
+		`use_line_present`,
+		`go 1.17
+		use baz`,
+		`foo`, `bar`,
+		`go 1.17
+		use (
+			baz
+		  foo
+		)
+		`,
+	},
+	{
+		`use_block_present`,
+		`go 1.17
+		use (
+			baz
+			quux
+		)
+		`,
+		`foo`, `bar`,
+		`go 1.17
+		use (
+			baz
+		  quux
+			foo
+		)
+		`,
+	},
+	{
+		`use_and_replace_present`,
+		`go 1.17
+		use baz
+		replace a => ./b
+		`,
+		`foo`, `bar`,
+		`go 1.17
+		use (
+			baz
+			foo
+		)
+		replace a => ./b
+		`,
+	},
+}
+
+var workDropUseTests = []struct {
+	desc string
+	in   string
+	path string
+	out  string
+}{
+	{
+		`empty`,
+		``,
+		`foo`,
+		``,
+	},
+	{
+		`go_stmt_only`,
+		`go 1.17
+		`,
+		`foo`,
+		`go 1.17
+		`,
+	},
+	{
+		`single_use`,
+		`go 1.17
+		use foo`,
+		`foo`,
+		`go 1.17
+		`,
+	},
+	{
+		`use_block`,
+		`go 1.17
+		use (
+			foo
+			bar
+			baz
+		)`,
+		`bar`,
+		`go 1.17
+		use (
+			foo
+			baz
+		)`,
+	},
+	{
+		`use_multi`,
+		`go 1.17
+		use (
+			foo
+			bar
+			baz
+		)
+		use foo
+		use quux
+		use foo`,
+		`foo`,
+		`go 1.17
+		use (
+			bar
+			baz
+		)
+		use quux`,
+	},
+}
+
+var workAddGoTests = []struct {
+	desc    string
+	in      string
+	version string
+	out     string
+}{
+	{
+		`empty`,
+		``,
+		`1.17`,
+		`go 1.17
+		`,
+	},
+	{
+		`comment`,
+		`// this is a comment`,
+		`1.17`,
+		`// this is a comment
+
+		go 1.17`,
+	},
+	{
+		`use_after_replace`,
+		`
+		replace example.com/foo => ../bar
+		use foo
+		`,
+		`1.17`,
+		`
+		go 1.17
+		replace example.com/foo => ../bar
+		use foo
+		`,
+	},
+	{
+		`use_before_replace`,
+		`use foo
+		replace example.com/foo => ../bar
+		`,
+		`1.17`,
+		`
+		go 1.17
+		use foo
+		replace example.com/foo => ../bar
+		`,
+	},
+	{
+		`use_only`,
+		`use foo
+		`,
+		`1.17`,
+		`
+		go 1.17
+		use foo
+		`,
+	},
+	{
+		`already_have_go`,
+		`go 1.17
+		`,
+		`1.18`,
+		`
+		go 1.18
+		`,
+	},
+}
+
+var workAddToolchainTests = []struct {
+	desc    string
+	in      string
+	version string
+	out     string
+}{
+	{
+		`empty`,
+		``,
+		`go1.17`,
+		`toolchain go1.17
+		`,
+	},
+	{
+		`aftergo`,
+		`// this is a comment
+		use foo
+
+		go 1.17
+
+		use bar
+		`,
+		`go1.17`,
+		`// this is a comment
+		use foo
+
+		go 1.17
+
+		toolchain go1.17
+
+		use bar
+		`,
+	},
+	{
+		`already_have_toolchain`,
+		`go 1.17
+
+		toolchain go1.18
+		`,
+		`go1.19`,
+		`go 1.17
+
+		toolchain go1.19
+		`,
+	},
+}
+
+var workSortBlocksTests = []struct {
+	desc, in, out string
+}{
+	{
+		`use_duplicates_not_removed`,
+		`go 1.17
+		use foo
+		use bar
+		use (
+			foo
+		)`,
+		`go 1.17
+		use foo
+		use bar
+		use (
+			foo
+		)`,
+	},
+	{
+		`replace_duplicates_removed`,
+		`go 1.17
+		use foo
+		replace x.y/z v1.0.0 => ./a
+		replace x.y/z v1.1.0 => ./b
+		replace (
+			x.y/z v1.0.0 => ./c
+		)
+		`,
+		`go 1.17
+		use foo
+		replace x.y/z v1.1.0 => ./b
+		replace (
+			x.y/z v1.0.0 => ./c
+		)
+		`,
+	},
+}
+
+func TestAddUse(t *testing.T) {
+	for _, tt := range workAddUseTests {
+		t.Run(tt.desc, func(t *testing.T) {
+			testWorkEdit(t, tt.in, tt.out, func(f *WorkFile) error {
+				return f.AddUse(tt.path, tt.modulePath)
+			})
+		})
+	}
+}
+
+func TestDropUse(t *testing.T) {
+	for _, tt := range workDropUseTests {
+		t.Run(tt.desc, func(t *testing.T) {
+			testWorkEdit(t, tt.in, tt.out, func(f *WorkFile) error {
+				if err := f.DropUse(tt.path); err != nil {
+					return err
+				}
+				f.Cleanup()
+				return nil
+			})
+		})
+	}
+}
+
+func TestWorkAddGo(t *testing.T) {
+	for _, tt := range workAddGoTests {
+		t.Run(tt.desc, func(t *testing.T) {
+			testWorkEdit(t, tt.in, tt.out, func(f *WorkFile) error {
+				return f.AddGoStmt(tt.version)
+			})
+		})
+	}
+}
+
+func TestWorkAddToolchain(t *testing.T) {
+	for _, tt := range workAddToolchainTests {
+		t.Run(tt.desc, func(t *testing.T) {
+			testWorkEdit(t, tt.in, tt.out, func(f *WorkFile) error {
+				return f.AddToolchainStmt(tt.version)
+			})
+		})
+	}
+}
+
+func TestWorkSortBlocks(t *testing.T) {
+	for _, tt := range workSortBlocksTests {
+		t.Run(tt.desc, func(t *testing.T) {
+			testWorkEdit(t, tt.in, tt.out, func(f *WorkFile) error {
+				f.SortBlocks()
+				return nil
+			})
+		})
+	}
+}
+
+// Test that when files in the testdata directory are parsed
+// and printed and parsed again, we get the same parse tree
+// both times.
+func TestWorkPrintParse(t *testing.T) {
+	outs, err := filepath.Glob("testdata/work/*")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, out := range outs {
+		out := out
+		name := filepath.Base(out)
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			data, err := os.ReadFile(out)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			base := "testdata/work/" + filepath.Base(out)
+			f, err := parse(base, data)
+			if err != nil {
+				t.Fatalf("parsing original: %v", err)
+			}
+
+			ndata := Format(f)
+			f2, err := parse(base, ndata)
+			if err != nil {
+				t.Fatalf("parsing reformatted: %v", err)
+			}
+
+			eq := eqchecker{file: base}
+			if err := eq.check(f, f2); err != nil {
+				t.Errorf("not equal (parse/Format/parse): %v", err)
+			}
+
+			pf1, err := ParseWork(base, data, nil)
+			if err != nil {
+				t.Errorf("should parse %v: %v", base, err)
+			}
+			if err == nil {
+				pf2, err := ParseWork(base, ndata, nil)
+				if err != nil {
+					t.Fatalf("Parsing reformatted: %v", err)
+				}
+				eq := eqchecker{file: base}
+				if err := eq.check(pf1, pf2); err != nil {
+					t.Errorf("not equal (parse/Format/Parse): %v", err)
+				}
+
+				ndata2 := Format(pf1.Syntax)
+				pf3, err := ParseWork(base, ndata2, nil)
+				if err != nil {
+					t.Fatalf("Parsing reformatted2: %v", err)
+				}
+				eq = eqchecker{file: base}
+				if err := eq.check(pf1, pf3); err != nil {
+					t.Errorf("not equal (Parse/Format/Parse): %v", err)
+				}
+				ndata = ndata2
+			}
+
+			if strings.HasSuffix(out, ".in") {
+				golden, err := os.ReadFile(strings.TrimSuffix(out, ".in") + ".golden")
+				if err != nil {
+					t.Fatal(err)
+				}
+				if !bytes.Equal(ndata, golden) {
+					t.Errorf("formatted %s incorrectly: diff shows -golden, +ours", base)
+					tdiff(t, string(golden), string(ndata))
+					return
+				}
+			}
+		})
+	}
+}
+
+func testWorkEdit(t *testing.T, in, want string, transform func(f *WorkFile) error) *WorkFile {
+	t.Helper()
+	parse := ParseWork
+	f, err := parse("in", []byte(in), nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	g, err := parse("out", []byte(want), nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	golden := Format(g.Syntax)
+
+	if err := transform(f); err != nil {
+		t.Fatal(err)
+	}
+	out := Format(f.Syntax)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(out, golden) {
+		t.Errorf("have:\n%s\nwant:\n%s", out, golden)
+	}
+
+	return f
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/module/module.go

@@ -0,0 +1,841 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package module defines the module.Version type along with support code.
+//
+// The [module.Version] type is a simple Path, Version pair:
+//
+//	type Version struct {
+//		Path string
+//		Version string
+//	}
+//
+// There are no restrictions imposed directly by use of this structure,
+// but additional checking functions, most notably [Check], verify that
+// a particular path, version pair is valid.
+//
+// # Escaped Paths
+//
+// Module paths appear as substrings of file system paths
+// (in the download cache) and of web server URLs in the proxy protocol.
+// In general we cannot rely on file systems to be case-sensitive,
+// nor can we rely on web servers, since they read from file systems.
+// That is, we cannot rely on the file system to keep rsc.io/QUOTE
+// and rsc.io/quote separate. Windows and macOS don't.
+// Instead, we must never require two different casings of a file path.
+// Because we want the download cache to match the proxy protocol,
+// and because we want the proxy protocol to be possible to serve
+// from a tree of static files (which might be stored on a case-insensitive
+// file system), the proxy protocol must never require two different casings
+// of a URL path either.
+//
+// One possibility would be to make the escaped form be the lowercase
+// hexadecimal encoding of the actual path bytes. This would avoid ever
+// needing different casings of a file path, but it would be fairly illegible
+// to most programmers when those paths appeared in the file system
+// (including in file paths in compiler errors and stack traces)
+// in web server logs, and so on. Instead, we want a safe escaped form that
+// leaves most paths unaltered.
+//
+// The safe escaped form is to replace every uppercase letter
+// with an exclamation mark followed by the letter's lowercase equivalent.
+//
+// For example,
+//
+//	github.com/Azure/azure-sdk-for-go ->  github.com/!azure/azure-sdk-for-go.
+//	github.com/GoogleCloudPlatform/cloudsql-proxy -> github.com/!google!cloud!platform/cloudsql-proxy
+//	github.com/Sirupsen/logrus -> github.com/!sirupsen/logrus.
+//
+// Import paths that avoid upper-case letters are left unchanged.
+// Note that because import paths are ASCII-only and avoid various
+// problematic punctuation (like : < and >), the escaped form is also ASCII-only
+// and avoids the same problematic punctuation.
+//
+// Import paths have never allowed exclamation marks, so there is no
+// need to define how to escape a literal !.
+//
+// # Unicode Restrictions
+//
+// Today, paths are disallowed from using Unicode.
+//
+// Although paths are currently disallowed from using Unicode,
+// we would like at some point to allow Unicode letters as well, to assume that
+// file systems and URLs are Unicode-safe (storing UTF-8), and apply
+// the !-for-uppercase convention for escaping them in the file system.
+// But there are at least two subtle considerations.
+//
+// First, note that not all case-fold equivalent distinct runes
+// form an upper/lower pair.
+// For example, U+004B ('K'), U+006B ('k'), and U+212A ('K' for Kelvin)
+// are three distinct runes that case-fold to each other.
+// When we do add Unicode letters, we must not assume that upper/lower
+// are the only case-equivalent pairs.
+// Perhaps the Kelvin symbol would be disallowed entirely, for example.
+// Or perhaps it would escape as "!!k", or perhaps as "(212A)".
+//
+// Second, it would be nice to allow Unicode marks as well as letters,
+// but marks include combining marks, and then we must deal not
+// only with case folding but also normalization: both U+00E9 ('é')
+// and U+0065 U+0301 ('e' followed by combining acute accent)
+// look the same on the page and are treated by some file systems
+// as the same path. If we do allow Unicode marks in paths, there
+// must be some kind of normalization to allow only one canonical
+// encoding of any character used in an import path.
+package module
+
+// IMPORTANT NOTE
+//
+// This file essentially defines the set of valid import paths for the go command.
+// There are many subtle considerations, including Unicode ambiguity,
+// security, network, and file system representations.
+//
+// This file also defines the set of valid module path and version combinations,
+// another topic with many subtle considerations.
+//
+// Changes to the semantics in this file require approval from rsc.
+
+import (
+	"errors"
+	"fmt"
+	"path"
+	"sort"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/mod/semver"
+)
+
+// A Version (for clients, a module.Version) is defined by a module path and version pair.
+// These are stored in their plain (unescaped) form.
+type Version struct {
+	// Path is a module path, like "golang.org/x/text" or "rsc.io/quote/v2".
+	Path string
+
+	// Version is usually a semantic version in canonical form.
+	// There are three exceptions to this general rule.
+	// First, the top-level target of a build has no specific version
+	// and uses Version = "".
+	// Second, during MVS calculations the version "none" is used
+	// to represent the decision to take no version of a given module.
+	// Third, filesystem paths found in "replace" directives are
+	// represented by a path with an empty version.
+	Version string `json:",omitempty"`
+}
+
+// String returns a representation of the Version suitable for logging
+// (Path@Version, or just Path if Version is empty).
+func (m Version) String() string {
+	if m.Version == "" {
+		return m.Path
+	}
+	return m.Path + "@" + m.Version
+}
+
+// A ModuleError indicates an error specific to a module.
+type ModuleError struct {
+	Path    string
+	Version string
+	Err     error
+}
+
+// VersionError returns a [ModuleError] derived from a [Version] and error,
+// or err itself if it is already such an error.
+func VersionError(v Version, err error) error {
+	var mErr *ModuleError
+	if errors.As(err, &mErr) && mErr.Path == v.Path && mErr.Version == v.Version {
+		return err
+	}
+	return &ModuleError{
+		Path:    v.Path,
+		Version: v.Version,
+		Err:     err,
+	}
+}
+
+func (e *ModuleError) Error() string {
+	if v, ok := e.Err.(*InvalidVersionError); ok {
+		return fmt.Sprintf("%s@%s: invalid %s: %v", e.Path, v.Version, v.noun(), v.Err)
+	}
+	if e.Version != "" {
+		return fmt.Sprintf("%s@%s: %v", e.Path, e.Version, e.Err)
+	}
+	return fmt.Sprintf("module %s: %v", e.Path, e.Err)
+}
+
+func (e *ModuleError) Unwrap() error { return e.Err }
+
+// An InvalidVersionError indicates an error specific to a version, with the
+// module path unknown or specified externally.
+//
+// A [ModuleError] may wrap an InvalidVersionError, but an InvalidVersionError
+// must not wrap a ModuleError.
+type InvalidVersionError struct {
+	Version string
+	Pseudo  bool
+	Err     error
+}
+
+// noun returns either "version" or "pseudo-version", depending on whether
+// e.Version is a pseudo-version.
+func (e *InvalidVersionError) noun() string {
+	if e.Pseudo {
+		return "pseudo-version"
+	}
+	return "version"
+}
+
+func (e *InvalidVersionError) Error() string {
+	return fmt.Sprintf("%s %q invalid: %s", e.noun(), e.Version, e.Err)
+}
+
+func (e *InvalidVersionError) Unwrap() error { return e.Err }
+
+// An InvalidPathError indicates a module, import, or file path doesn't
+// satisfy all naming constraints. See [CheckPath], [CheckImportPath],
+// and [CheckFilePath] for specific restrictions.
+type InvalidPathError struct {
+	Kind string // "module", "import", or "file"
+	Path string
+	Err  error
+}
+
+func (e *InvalidPathError) Error() string {
+	return fmt.Sprintf("malformed %s path %q: %v", e.Kind, e.Path, e.Err)
+}
+
+func (e *InvalidPathError) Unwrap() error { return e.Err }
+
+// Check checks that a given module path, version pair is valid.
+// In addition to the path being a valid module path
+// and the version being a valid semantic version,
+// the two must correspond.
+// For example, the path "yaml/v2" only corresponds to
+// semantic versions beginning with "v2.".
+func Check(path, version string) error {
+	if err := CheckPath(path); err != nil {
+		return err
+	}
+	if !semver.IsValid(version) {
+		return &ModuleError{
+			Path: path,
+			Err:  &InvalidVersionError{Version: version, Err: errors.New("not a semantic version")},
+		}
+	}
+	_, pathMajor, _ := SplitPathVersion(path)
+	if err := CheckPathMajor(version, pathMajor); err != nil {
+		return &ModuleError{Path: path, Err: err}
+	}
+	return nil
+}
+
+// firstPathOK reports whether r can appear in the first element of a module path.
+// The first element of the path must be an LDH domain name, at least for now.
+// To avoid case ambiguity, the domain name must be entirely lower case.
+func firstPathOK(r rune) bool {
+	return r == '-' || r == '.' ||
+		'0' <= r && r <= '9' ||
+		'a' <= r && r <= 'z'
+}
+
+// modPathOK reports whether r can appear in a module path element.
+// Paths can be ASCII letters, ASCII digits, and limited ASCII punctuation: - . _ and ~.
+//
+// This matches what "go get" has historically recognized in import paths,
+// and avoids confusing sequences like '%20' or '+' that would change meaning
+// if used in a URL.
+//
+// TODO(rsc): We would like to allow Unicode letters, but that requires additional
+// care in the safe encoding (see "escaped paths" above).
+func modPathOK(r rune) bool {
+	if r < utf8.RuneSelf {
+		return r == '-' || r == '.' || r == '_' || r == '~' ||
+			'0' <= r && r <= '9' ||
+			'A' <= r && r <= 'Z' ||
+			'a' <= r && r <= 'z'
+	}
+	return false
+}
+
+// importPathOK reports whether r can appear in a package import path element.
+//
+// Import paths are intermediate between module paths and file paths: we allow
+// disallow characters that would be confusing or ambiguous as arguments to
+// 'go get' (such as '@' and ' ' ), but allow certain characters that are
+// otherwise-unambiguous on the command line and historically used for some
+// binary names (such as '++' as a suffix for compiler binaries and wrappers).
+func importPathOK(r rune) bool {
+	return modPathOK(r) || r == '+'
+}
+
+// fileNameOK reports whether r can appear in a file name.
+// For now we allow all Unicode letters but otherwise limit to pathOK plus a few more punctuation characters.
+// If we expand the set of allowed characters here, we have to
+// work harder at detecting potential case-folding and normalization collisions.
+// See note about "escaped paths" above.
+func fileNameOK(r rune) bool {
+	if r < utf8.RuneSelf {
+		// Entire set of ASCII punctuation, from which we remove characters:
+		//     ! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~
+		// We disallow some shell special characters: " ' * < > ? ` |
+		// (Note that some of those are disallowed by the Windows file system as well.)
+		// We also disallow path separators / : and \ (fileNameOK is only called on path element characters).
+		// We allow spaces (U+0020) in file names.
+		const allowed = "!#$%&()+,-.=@[]^_{}~ "
+		if '0' <= r && r <= '9' || 'A' <= r && r <= 'Z' || 'a' <= r && r <= 'z' {
+			return true
+		}
+		return strings.ContainsRune(allowed, r)
+	}
+	// It may be OK to add more ASCII punctuation here, but only carefully.
+	// For example Windows disallows < > \, and macOS disallows :, so we must not allow those.
+	return unicode.IsLetter(r)
+}
+
+// CheckPath checks that a module path is valid.
+// A valid module path is a valid import path, as checked by [CheckImportPath],
+// with three additional constraints.
+// First, the leading path element (up to the first slash, if any),
+// by convention a domain name, must contain only lower-case ASCII letters,
+// ASCII digits, dots (U+002E), and dashes (U+002D);
+// it must contain at least one dot and cannot start with a dash.
+// Second, for a final path element of the form /vN, where N looks numeric
+// (ASCII digits and dots) must not begin with a leading zero, must not be /v1,
+// and must not contain any dots. For paths beginning with "gopkg.in/",
+// this second requirement is replaced by a requirement that the path
+// follow the gopkg.in server's conventions.
+// Third, no path element may begin with a dot.
+func CheckPath(path string) (err error) {
+	defer func() {
+		if err != nil {
+			err = &InvalidPathError{Kind: "module", Path: path, Err: err}
+		}
+	}()
+
+	if err := checkPath(path, modulePath); err != nil {
+		return err
+	}
+	i := strings.Index(path, "/")
+	if i < 0 {
+		i = len(path)
+	}
+	if i == 0 {
+		return fmt.Errorf("leading slash")
+	}
+	if !strings.Contains(path[:i], ".") {
+		return fmt.Errorf("missing dot in first path element")
+	}
+	if path[0] == '-' {
+		return fmt.Errorf("leading dash in first path element")
+	}
+	for _, r := range path[:i] {
+		if !firstPathOK(r) {
+			return fmt.Errorf("invalid char %q in first path element", r)
+		}
+	}
+	if _, _, ok := SplitPathVersion(path); !ok {
+		return fmt.Errorf("invalid version")
+	}
+	return nil
+}
+
+// CheckImportPath checks that an import path is valid.
+//
+// A valid import path consists of one or more valid path elements
+// separated by slashes (U+002F). (It must not begin with nor end in a slash.)
+//
+// A valid path element is a non-empty string made up of
+// ASCII letters, ASCII digits, and limited ASCII punctuation: - . _ and ~.
+// It must not end with a dot (U+002E), nor contain two dots in a row.
+//
+// The element prefix up to the first dot must not be a reserved file name
+// on Windows, regardless of case (CON, com1, NuL, and so on). The element
+// must not have a suffix of a tilde followed by one or more ASCII digits
+// (to exclude paths elements that look like Windows short-names).
+//
+// CheckImportPath may be less restrictive in the future, but see the
+// top-level package documentation for additional information about
+// subtleties of Unicode.
+func CheckImportPath(path string) error {
+	if err := checkPath(path, importPath); err != nil {
+		return &InvalidPathError{Kind: "import", Path: path, Err: err}
+	}
+	return nil
+}
+
+// pathKind indicates what kind of path we're checking. Module paths,
+// import paths, and file paths have different restrictions.
+type pathKind int
+
+const (
+	modulePath pathKind = iota
+	importPath
+	filePath
+)
+
+// checkPath checks that a general path is valid. kind indicates what
+// specific constraints should be applied.
+//
+// checkPath returns an error describing why the path is not valid.
+// Because these checks apply to module, import, and file paths,
+// and because other checks may be applied, the caller is expected to wrap
+// this error with [InvalidPathError].
+func checkPath(path string, kind pathKind) error {
+	if !utf8.ValidString(path) {
+		return fmt.Errorf("invalid UTF-8")
+	}
+	if path == "" {
+		return fmt.Errorf("empty string")
+	}
+	if path[0] == '-' && kind != filePath {
+		return fmt.Errorf("leading dash")
+	}
+	if strings.Contains(path, "//") {
+		return fmt.Errorf("double slash")
+	}
+	if path[len(path)-1] == '/' {
+		return fmt.Errorf("trailing slash")
+	}
+	elemStart := 0
+	for i, r := range path {
+		if r == '/' {
+			if err := checkElem(path[elemStart:i], kind); err != nil {
+				return err
+			}
+			elemStart = i + 1
+		}
+	}
+	if err := checkElem(path[elemStart:], kind); err != nil {
+		return err
+	}
+	return nil
+}
+
+// checkElem checks whether an individual path element is valid.
+func checkElem(elem string, kind pathKind) error {
+	if elem == "" {
+		return fmt.Errorf("empty path element")
+	}
+	if strings.Count(elem, ".") == len(elem) {
+		return fmt.Errorf("invalid path element %q", elem)
+	}
+	if elem[0] == '.' && kind == modulePath {
+		return fmt.Errorf("leading dot in path element")
+	}
+	if elem[len(elem)-1] == '.' {
+		return fmt.Errorf("trailing dot in path element")
+	}
+	for _, r := range elem {
+		ok := false
+		switch kind {
+		case modulePath:
+			ok = modPathOK(r)
+		case importPath:
+			ok = importPathOK(r)
+		case filePath:
+			ok = fileNameOK(r)
+		default:
+			panic(fmt.Sprintf("internal error: invalid kind %v", kind))
+		}
+		if !ok {
+			return fmt.Errorf("invalid char %q", r)
+		}
+	}
+
+	// Windows disallows a bunch of path elements, sadly.
+	// See https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file
+	short := elem
+	if i := strings.Index(short, "."); i >= 0 {
+		short = short[:i]
+	}
+	for _, bad := range badWindowsNames {
+		if strings.EqualFold(bad, short) {
+			return fmt.Errorf("%q disallowed as path element component on Windows", short)
+		}
+	}
+
+	if kind == filePath {
+		// don't check for Windows short-names in file names. They're
+		// only an issue for import paths.
+		return nil
+	}
+
+	// Reject path components that look like Windows short-names.
+	// Those usually end in a tilde followed by one or more ASCII digits.
+	if tilde := strings.LastIndexByte(short, '~'); tilde >= 0 && tilde < len(short)-1 {
+		suffix := short[tilde+1:]
+		suffixIsDigits := true
+		for _, r := range suffix {
+			if r < '0' || r > '9' {
+				suffixIsDigits = false
+				break
+			}
+		}
+		if suffixIsDigits {
+			return fmt.Errorf("trailing tilde and digits in path element")
+		}
+	}
+
+	return nil
+}
+
+// CheckFilePath checks that a slash-separated file path is valid.
+// The definition of a valid file path is the same as the definition
+// of a valid import path except that the set of allowed characters is larger:
+// all Unicode letters, ASCII digits, the ASCII space character (U+0020),
+// and the ASCII punctuation characters
+// “!#$%&()+,-.=@[]^_{}~”.
+// (The excluded punctuation characters, " * < > ? ` ' | / \ and :,
+// have special meanings in certain shells or operating systems.)
+//
+// CheckFilePath may be less restrictive in the future, but see the
+// top-level package documentation for additional information about
+// subtleties of Unicode.
+func CheckFilePath(path string) error {
+	if err := checkPath(path, filePath); err != nil {
+		return &InvalidPathError{Kind: "file", Path: path, Err: err}
+	}
+	return nil
+}
+
+// badWindowsNames are the reserved file path elements on Windows.
+// See https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file
+var badWindowsNames = []string{
+	"CON",
+	"PRN",
+	"AUX",
+	"NUL",
+	"COM1",
+	"COM2",
+	"COM3",
+	"COM4",
+	"COM5",
+	"COM6",
+	"COM7",
+	"COM8",
+	"COM9",
+	"LPT1",
+	"LPT2",
+	"LPT3",
+	"LPT4",
+	"LPT5",
+	"LPT6",
+	"LPT7",
+	"LPT8",
+	"LPT9",
+}
+
+// SplitPathVersion returns prefix and major version such that prefix+pathMajor == path
+// and version is either empty or "/vN" for N >= 2.
+// As a special case, gopkg.in paths are recognized directly;
+// they require ".vN" instead of "/vN", and for all N, not just N >= 2.
+// SplitPathVersion returns with ok = false when presented with
+// a path whose last path element does not satisfy the constraints
+// applied by [CheckPath], such as "example.com/pkg/v1" or "example.com/pkg/v1.2".
+func SplitPathVersion(path string) (prefix, pathMajor string, ok bool) {
+	if strings.HasPrefix(path, "gopkg.in/") {
+		return splitGopkgIn(path)
+	}
+
+	i := len(path)
+	dot := false
+	for i > 0 && ('0' <= path[i-1] && path[i-1] <= '9' || path[i-1] == '.') {
+		if path[i-1] == '.' {
+			dot = true
+		}
+		i--
+	}
+	if i <= 1 || i == len(path) || path[i-1] != 'v' || path[i-2] != '/' {
+		return path, "", true
+	}
+	prefix, pathMajor = path[:i-2], path[i-2:]
+	if dot || len(pathMajor) <= 2 || pathMajor[2] == '0' || pathMajor == "/v1" {
+		return path, "", false
+	}
+	return prefix, pathMajor, true
+}
+
+// splitGopkgIn is like SplitPathVersion but only for gopkg.in paths.
+func splitGopkgIn(path string) (prefix, pathMajor string, ok bool) {
+	if !strings.HasPrefix(path, "gopkg.in/") {
+		return path, "", false
+	}
+	i := len(path)
+	if strings.HasSuffix(path, "-unstable") {
+		i -= len("-unstable")
+	}
+	for i > 0 && ('0' <= path[i-1] && path[i-1] <= '9') {
+		i--
+	}
+	if i <= 1 || path[i-1] != 'v' || path[i-2] != '.' {
+		// All gopkg.in paths must end in vN for some N.
+		return path, "", false
+	}
+	prefix, pathMajor = path[:i-2], path[i-2:]
+	if len(pathMajor) <= 2 || pathMajor[2] == '0' && pathMajor != ".v0" {
+		return path, "", false
+	}
+	return prefix, pathMajor, true
+}
+
+// MatchPathMajor reports whether the semantic version v
+// matches the path major version pathMajor.
+//
+// MatchPathMajor returns true if and only if [CheckPathMajor] returns nil.
+func MatchPathMajor(v, pathMajor string) bool {
+	return CheckPathMajor(v, pathMajor) == nil
+}
+
+// CheckPathMajor returns a non-nil error if the semantic version v
+// does not match the path major version pathMajor.
+func CheckPathMajor(v, pathMajor string) error {
+	// TODO(jayconrod): return errors or panic for invalid inputs. This function
+	// (and others) was covered by integration tests for cmd/go, and surrounding
+	// code protected against invalid inputs like non-canonical versions.
+	if strings.HasPrefix(pathMajor, ".v") && strings.HasSuffix(pathMajor, "-unstable") {
+		pathMajor = strings.TrimSuffix(pathMajor, "-unstable")
+	}
+	if strings.HasPrefix(v, "v0.0.0-") && pathMajor == ".v1" {
+		// Allow old bug in pseudo-versions that generated v0.0.0- pseudoversion for gopkg .v1.
+		// For example, gopkg.in/yaml.v2@v2.2.1's go.mod requires gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405.
+		return nil
+	}
+	m := semver.Major(v)
+	if pathMajor == "" {
+		if m == "v0" || m == "v1" || semver.Build(v) == "+incompatible" {
+			return nil
+		}
+		pathMajor = "v0 or v1"
+	} else if pathMajor[0] == '/' || pathMajor[0] == '.' {
+		if m == pathMajor[1:] {
+			return nil
+		}
+		pathMajor = pathMajor[1:]
+	}
+	return &InvalidVersionError{
+		Version: v,
+		Err:     fmt.Errorf("should be %s, not %s", pathMajor, semver.Major(v)),
+	}
+}
+
+// PathMajorPrefix returns the major-version tag prefix implied by pathMajor.
+// An empty PathMajorPrefix allows either v0 or v1.
+//
+// Note that [MatchPathMajor] may accept some versions that do not actually begin
+// with this prefix: namely, it accepts a 'v0.0.0-' prefix for a '.v1'
+// pathMajor, even though that pathMajor implies 'v1' tagging.
+func PathMajorPrefix(pathMajor string) string {
+	if pathMajor == "" {
+		return ""
+	}
+	if pathMajor[0] != '/' && pathMajor[0] != '.' {
+		panic("pathMajor suffix " + pathMajor + " passed to PathMajorPrefix lacks separator")
+	}
+	if strings.HasPrefix(pathMajor, ".v") && strings.HasSuffix(pathMajor, "-unstable") {
+		pathMajor = strings.TrimSuffix(pathMajor, "-unstable")
+	}
+	m := pathMajor[1:]
+	if m != semver.Major(m) {
+		panic("pathMajor suffix " + pathMajor + "passed to PathMajorPrefix is not a valid major version")
+	}
+	return m
+}
+
+// CanonicalVersion returns the canonical form of the version string v.
+// It is the same as [semver.Canonical] except that it preserves the special build suffix "+incompatible".
+func CanonicalVersion(v string) string {
+	cv := semver.Canonical(v)
+	if semver.Build(v) == "+incompatible" {
+		cv += "+incompatible"
+	}
+	return cv
+}
+
+// Sort sorts the list by Path, breaking ties by comparing [Version] fields.
+// The Version fields are interpreted as semantic versions (using [semver.Compare])
+// optionally followed by a tie-breaking suffix introduced by a slash character,
+// like in "v0.0.1/go.mod".
+func Sort(list []Version) {
+	sort.Slice(list, func(i, j int) bool {
+		mi := list[i]
+		mj := list[j]
+		if mi.Path != mj.Path {
+			return mi.Path < mj.Path
+		}
+		// To help go.sum formatting, allow version/file.
+		// Compare semver prefix by semver rules,
+		// file by string order.
+		vi := mi.Version
+		vj := mj.Version
+		var fi, fj string
+		if k := strings.Index(vi, "/"); k >= 0 {
+			vi, fi = vi[:k], vi[k:]
+		}
+		if k := strings.Index(vj, "/"); k >= 0 {
+			vj, fj = vj[:k], vj[k:]
+		}
+		if vi != vj {
+			return semver.Compare(vi, vj) < 0
+		}
+		return fi < fj
+	})
+}
+
+// EscapePath returns the escaped form of the given module path.
+// It fails if the module path is invalid.
+func EscapePath(path string) (escaped string, err error) {
+	if err := CheckPath(path); err != nil {
+		return "", err
+	}
+
+	return escapeString(path)
+}
+
+// EscapeVersion returns the escaped form of the given module version.
+// Versions are allowed to be in non-semver form but must be valid file names
+// and not contain exclamation marks.
+func EscapeVersion(v string) (escaped string, err error) {
+	if err := checkElem(v, filePath); err != nil || strings.Contains(v, "!") {
+		return "", &InvalidVersionError{
+			Version: v,
+			Err:     fmt.Errorf("disallowed version string"),
+		}
+	}
+	return escapeString(v)
+}
+
+func escapeString(s string) (escaped string, err error) {
+	haveUpper := false
+	for _, r := range s {
+		if r == '!' || r >= utf8.RuneSelf {
+			// This should be disallowed by CheckPath, but diagnose anyway.
+			// The correctness of the escaping loop below depends on it.
+			return "", fmt.Errorf("internal error: inconsistency in EscapePath")
+		}
+		if 'A' <= r && r <= 'Z' {
+			haveUpper = true
+		}
+	}
+
+	if !haveUpper {
+		return s, nil
+	}
+
+	var buf []byte
+	for _, r := range s {
+		if 'A' <= r && r <= 'Z' {
+			buf = append(buf, '!', byte(r+'a'-'A'))
+		} else {
+			buf = append(buf, byte(r))
+		}
+	}
+	return string(buf), nil
+}
+
+// UnescapePath returns the module path for the given escaped path.
+// It fails if the escaped path is invalid or describes an invalid path.
+func UnescapePath(escaped string) (path string, err error) {
+	path, ok := unescapeString(escaped)
+	if !ok {
+		return "", fmt.Errorf("invalid escaped module path %q", escaped)
+	}
+	if err := CheckPath(path); err != nil {
+		return "", fmt.Errorf("invalid escaped module path %q: %v", escaped, err)
+	}
+	return path, nil
+}
+
+// UnescapeVersion returns the version string for the given escaped version.
+// It fails if the escaped form is invalid or describes an invalid version.
+// Versions are allowed to be in non-semver form but must be valid file names
+// and not contain exclamation marks.
+func UnescapeVersion(escaped string) (v string, err error) {
+	v, ok := unescapeString(escaped)
+	if !ok {
+		return "", fmt.Errorf("invalid escaped version %q", escaped)
+	}
+	if err := checkElem(v, filePath); err != nil {
+		return "", fmt.Errorf("invalid escaped version %q: %v", v, err)
+	}
+	return v, nil
+}
+
+func unescapeString(escaped string) (string, bool) {
+	var buf []byte
+
+	bang := false
+	for _, r := range escaped {
+		if r >= utf8.RuneSelf {
+			return "", false
+		}
+		if bang {
+			bang = false
+			if r < 'a' || 'z' < r {
+				return "", false
+			}
+			buf = append(buf, byte(r+'A'-'a'))
+			continue
+		}
+		if r == '!' {
+			bang = true
+			continue
+		}
+		if 'A' <= r && r <= 'Z' {
+			return "", false
+		}
+		buf = append(buf, byte(r))
+	}
+	if bang {
+		return "", false
+	}
+	return string(buf), true
+}
+
+// MatchPrefixPatterns reports whether any path prefix of target matches one of
+// the glob patterns (as defined by [path.Match]) in the comma-separated globs
+// list. This implements the algorithm used when matching a module path to the
+// GOPRIVATE environment variable, as described by 'go help module-private'.
+//
+// It ignores any empty or malformed patterns in the list.
+// Trailing slashes on patterns are ignored.
+func MatchPrefixPatterns(globs, target string) bool {
+	for globs != "" {
+		// Extract next non-empty glob in comma-separated list.
+		var glob string
+		if i := strings.Index(globs, ","); i >= 0 {
+			glob, globs = globs[:i], globs[i+1:]
+		} else {
+			glob, globs = globs, ""
+		}
+		glob = strings.TrimSuffix(glob, "/")
+		if glob == "" {
+			continue
+		}
+
+		// A glob with N+1 path elements (N slashes) needs to be matched
+		// against the first N+1 path elements of target,
+		// which end just before the N+1'th slash.
+		n := strings.Count(glob, "/")
+		prefix := target
+		// Walk target, counting slashes, truncating at the N+1'th slash.
+		for i := 0; i < len(target); i++ {
+			if target[i] == '/' {
+				if n == 0 {
+					prefix = target[:i]
+					break
+				}
+				n--
+			}
+		}
+		if n > 0 {
+			// Not enough prefix elements.
+			continue
+		}
+		matched, _ := path.Match(glob, prefix)
+		if matched {
+			return true
+		}
+	}
+	return false
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/module/module_test.go

@@ -0,0 +1,389 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package module
+
+import "testing"
+
+var checkTests = []struct {
+	path    string
+	version string
+	ok      bool
+}{
+	{"rsc.io/quote", "0.1.0", false},
+	{"rsc io/quote", "v1.0.0", false},
+
+	{"github.com/go-yaml/yaml", "v0.8.0", true},
+	{"github.com/go-yaml/yaml", "v1.0.0", true},
+	{"github.com/go-yaml/yaml", "v2.0.0", false},
+	{"github.com/go-yaml/yaml", "v2.1.5", false},
+	{"github.com/go-yaml/yaml", "v3.0.0", false},
+
+	{"github.com/go-yaml/yaml/v2", "v1.0.0", false},
+	{"github.com/go-yaml/yaml/v2", "v2.0.0", true},
+	{"github.com/go-yaml/yaml/v2", "v2.1.5", true},
+	{"github.com/go-yaml/yaml/v2", "v3.0.0", false},
+
+	{"gopkg.in/yaml.v0", "v0.8.0", true},
+	{"gopkg.in/yaml.v0", "v1.0.0", false},
+	{"gopkg.in/yaml.v0", "v2.0.0", false},
+	{"gopkg.in/yaml.v0", "v2.1.5", false},
+	{"gopkg.in/yaml.v0", "v3.0.0", false},
+
+	{"gopkg.in/yaml.v1", "v0.8.0", false},
+	{"gopkg.in/yaml.v1", "v1.0.0", true},
+	{"gopkg.in/yaml.v1", "v2.0.0", false},
+	{"gopkg.in/yaml.v1", "v2.1.5", false},
+	{"gopkg.in/yaml.v1", "v3.0.0", false},
+
+	// For gopkg.in, .v1 means v1 only (not v0).
+	// But early versions of vgo still generated v0 pseudo-versions for it.
+	// Even though now we'd generate those as v1 pseudo-versions,
+	// we accept the old pseudo-versions to avoid breaking existing go.mod files.
+	// For example gopkg.in/yaml.v2@v2.2.1's go.mod requires check.v1 at a v0 pseudo-version.
+	{"gopkg.in/check.v1", "v0.0.0", false},
+	{"gopkg.in/check.v1", "v0.0.0-20160102150405-abcdef123456", true},
+
+	{"gopkg.in/yaml.v2", "v1.0.0", false},
+	{"gopkg.in/yaml.v2", "v2.0.0", true},
+	{"gopkg.in/yaml.v2", "v2.1.5", true},
+	{"gopkg.in/yaml.v2", "v3.0.0", false},
+
+	{"rsc.io/quote", "v17.0.0", false},
+	{"rsc.io/quote", "v17.0.0+incompatible", true},
+}
+
+func TestCheck(t *testing.T) {
+	for _, tt := range checkTests {
+		err := Check(tt.path, tt.version)
+		if tt.ok && err != nil {
+			t.Errorf("Check(%q, %q) = %v, wanted nil error", tt.path, tt.version, err)
+		} else if !tt.ok && err == nil {
+			t.Errorf("Check(%q, %q) succeeded, wanted error", tt.path, tt.version)
+		}
+	}
+}
+
+var checkPathTests = []struct {
+	path     string
+	ok       bool
+	importOK bool
+	fileOK   bool
+}{
+	{"x.y/z", true, true, true},
+	{"x.y", true, true, true},
+
+	{"", false, false, false},
+	{"x.y/\xFFz", false, false, false},
+	{"/x.y/z", false, false, false},
+	{"x./z", false, false, false},
+	{".x/z", false, true, true},
+	{"-x/z", false, false, true},
+	{"x..y/z", true, true, true},
+	{"x.y/z/../../w", false, false, false},
+	{"x.y//z", false, false, false},
+	{"x.y/z//w", false, false, false},
+	{"x.y/z/", false, false, false},
+
+	{"x.y/z/v0", false, true, true},
+	{"x.y/z/v1", false, true, true},
+	{"x.y/z/v2", true, true, true},
+	{"x.y/z/v2.0", false, true, true},
+	{"X.y/z", false, true, true},
+
+	{"!x.y/z", false, false, true},
+	{"_x.y/z", false, true, true},
+	{"x.y!/z", false, false, true},
+	{"x.y\"/z", false, false, false},
+	{"x.y#/z", false, false, true},
+	{"x.y$/z", false, false, true},
+	{"x.y%/z", false, false, true},
+	{"x.y&/z", false, false, true},
+	{"x.y'/z", false, false, false},
+	{"x.y(/z", false, false, true},
+	{"x.y)/z", false, false, true},
+	{"x.y*/z", false, false, false},
+	{"x.y+/z", false, true, true},
+	{"x.y,/z", false, false, true},
+	{"x.y-/z", true, true, true},
+	{"x.y./zt", false, false, false},
+	{"x.y:/z", false, false, false},
+	{"x.y;/z", false, false, false},
+	{"x.y</z", false, false, false},
+	{"x.y=/z", false, false, true},
+	{"x.y>/z", false, false, false},
+	{"x.y?/z", false, false, false},
+	{"x.y@/z", false, false, true},
+	{"x.y[/z", false, false, true},
+	{"x.y\\/z", false, false, false},
+	{"x.y]/z", false, false, true},
+	{"x.y^/z", false, false, true},
+	{"x.y_/z", false, true, true},
+	{"x.y`/z", false, false, false},
+	{"x.y{/z", false, false, true},
+	{"x.y}/z", false, false, true},
+	{"x.y~/z", false, true, true},
+	{"x.y/z!", false, false, true},
+	{"x.y/z\"", false, false, false},
+	{"x.y/z#", false, false, true},
+	{"x.y/z$", false, false, true},
+	{"x.y/z%", false, false, true},
+	{"x.y/z&", false, false, true},
+	{"x.y/z'", false, false, false},
+	{"x.y/z(", false, false, true},
+	{"x.y/z)", false, false, true},
+	{"x.y/z*", false, false, false},
+	{"x.y/z++", false, true, true},
+	{"x.y/z,", false, false, true},
+	{"x.y/z-", true, true, true},
+	{"x.y/z.t", true, true, true},
+	{"x.y/z/t", true, true, true},
+	{"x.y/z:", false, false, false},
+	{"x.y/z;", false, false, false},
+	{"x.y/z<", false, false, false},
+	{"x.y/z=", false, false, true},
+	{"x.y/z>", false, false, false},
+	{"x.y/z?", false, false, false},
+	{"x.y/z@", false, false, true},
+	{"x.y/z[", false, false, true},
+	{"x.y/z\\", false, false, false},
+	{"x.y/z]", false, false, true},
+	{"x.y/z^", false, false, true},
+	{"x.y/z_", true, true, true},
+	{"x.y/z`", false, false, false},
+	{"x.y/z{", false, false, true},
+	{"x.y/z}", false, false, true},
+	{"x.y/z~", true, true, true},
+	{"x.y/x.foo", true, true, true},
+	{"x.y/aux.foo", false, false, false},
+	{"x.y/prn", false, false, false},
+	{"x.y/prn2", true, true, true},
+	{"x.y/com", true, true, true},
+	{"x.y/com1", false, false, false},
+	{"x.y/com1.txt", false, false, false},
+	{"x.y/calm1", true, true, true},
+	{"x.y/z~", true, true, true},
+	{"x.y/z~0", false, false, true},
+	{"x.y/z~09", false, false, true},
+	{"x.y/z09", true, true, true},
+	{"x.y/z09~", true, true, true},
+	{"x.y/z09~09z", true, true, true},
+	{"x.y/z09~09z~09", false, false, true},
+	{"github.com/!123/logrus", false, false, true},
+
+	// TODO: CL 41822 allowed Unicode letters in old "go get"
+	// without due consideration of the implications, and only on github.com (!).
+	// For now, we disallow non-ASCII characters in module mode,
+	// in both module paths and general import paths,
+	// until we can get the implications right.
+	// When we do, we'll enable them everywhere, not just for GitHub.
+	{"github.com/user/unicode/испытание", false, false, true},
+
+	{"../x", false, false, false},
+	{"./y", false, false, false},
+	{"x:y", false, false, false},
+	{`\temp\foo`, false, false, false},
+	{".gitignore", false, true, true},
+	{".github/ISSUE_TEMPLATE", false, true, true},
+	{"x☺y", false, false, false},
+}
+
+func TestCheckPath(t *testing.T) {
+	for _, tt := range checkPathTests {
+		err := CheckPath(tt.path)
+		if tt.ok && err != nil {
+			t.Errorf("CheckPath(%q) = %v, wanted nil error", tt.path, err)
+		} else if !tt.ok && err == nil {
+			t.Errorf("CheckPath(%q) succeeded, wanted error", tt.path)
+		}
+
+		err = CheckImportPath(tt.path)
+		if tt.importOK && err != nil {
+			t.Errorf("CheckImportPath(%q) = %v, wanted nil error", tt.path, err)
+		} else if !tt.importOK && err == nil {
+			t.Errorf("CheckImportPath(%q) succeeded, wanted error", tt.path)
+		}
+
+		err = CheckFilePath(tt.path)
+		if tt.fileOK && err != nil {
+			t.Errorf("CheckFilePath(%q) = %v, wanted nil error", tt.path, err)
+		} else if !tt.fileOK && err == nil {
+			t.Errorf("CheckFilePath(%q) succeeded, wanted error", tt.path)
+		}
+	}
+}
+
+var splitPathVersionTests = []struct {
+	pathPrefix string
+	version    string
+}{
+	{"x.y/z", ""},
+	{"x.y/z", "/v2"},
+	{"x.y/z", "/v3"},
+	{"x.y/v", ""},
+	{"gopkg.in/yaml", ".v0"},
+	{"gopkg.in/yaml", ".v1"},
+	{"gopkg.in/yaml", ".v2"},
+	{"gopkg.in/yaml", ".v3"},
+}
+
+func TestSplitPathVersion(t *testing.T) {
+	for _, tt := range splitPathVersionTests {
+		pathPrefix, version, ok := SplitPathVersion(tt.pathPrefix + tt.version)
+		if pathPrefix != tt.pathPrefix || version != tt.version || !ok {
+			t.Errorf("SplitPathVersion(%q) = %q, %q, %v, want %q, %q, true", tt.pathPrefix+tt.version, pathPrefix, version, ok, tt.pathPrefix, tt.version)
+		}
+	}
+
+	for _, tt := range checkPathTests {
+		pathPrefix, version, ok := SplitPathVersion(tt.path)
+		if pathPrefix+version != tt.path {
+			t.Errorf("SplitPathVersion(%q) = %q, %q, %v, doesn't add to input", tt.path, pathPrefix, version, ok)
+		}
+	}
+}
+
+var escapeTests = []struct {
+	path string
+	esc  string // empty means same as path
+}{
+	{path: "ascii.com/abcdefghijklmnopqrstuvwxyz.-/~_0123456789"},
+	{path: "github.com/GoogleCloudPlatform/omega", esc: "github.com/!google!cloud!platform/omega"},
+}
+
+func TestEscapePath(t *testing.T) {
+	// Check invalid paths.
+	for _, tt := range checkPathTests {
+		if !tt.ok {
+			_, err := EscapePath(tt.path)
+			if err == nil {
+				t.Errorf("EscapePath(%q): succeeded, want error (invalid path)", tt.path)
+			}
+		}
+	}
+
+	// Check encodings.
+	for _, tt := range escapeTests {
+		esc, err := EscapePath(tt.path)
+		if err != nil {
+			t.Errorf("EscapePath(%q): unexpected error: %v", tt.path, err)
+			continue
+		}
+		want := tt.esc
+		if want == "" {
+			want = tt.path
+		}
+		if esc != want {
+			t.Errorf("EscapePath(%q) = %q, want %q", tt.path, esc, want)
+		}
+	}
+}
+
+var badUnescape = []string{
+	"github.com/GoogleCloudPlatform/omega",
+	"github.com/!google!cloud!platform!/omega",
+	"github.com/!0google!cloud!platform/omega",
+	"github.com/!_google!cloud!platform/omega",
+	"github.com/!!google!cloud!platform/omega",
+	"",
+}
+
+func TestUnescapePath(t *testing.T) {
+	// Check invalid decodings.
+	for _, bad := range badUnescape {
+		_, err := UnescapePath(bad)
+		if err == nil {
+			t.Errorf("UnescapePath(%q): succeeded, want error (invalid decoding)", bad)
+		}
+	}
+
+	// Check invalid paths (or maybe decodings).
+	for _, tt := range checkPathTests {
+		if !tt.ok {
+			path, err := UnescapePath(tt.path)
+			if err == nil {
+				t.Errorf("UnescapePath(%q) = %q, want error (invalid path)", tt.path, path)
+			}
+		}
+	}
+
+	// Check encodings.
+	for _, tt := range escapeTests {
+		esc := tt.esc
+		if esc == "" {
+			esc = tt.path
+		}
+		path, err := UnescapePath(esc)
+		if err != nil {
+			t.Errorf("UnescapePath(%q): unexpected error: %v", esc, err)
+			continue
+		}
+		if path != tt.path {
+			t.Errorf("UnescapePath(%q) = %q, want %q", esc, path, tt.path)
+		}
+	}
+}
+
+func TestMatchPathMajor(t *testing.T) {
+	for _, test := range []struct {
+		v, pathMajor string
+		want         bool
+	}{
+		{"v0.0.0", "", true},
+		{"v0.0.0", "/v2", false},
+		{"v0.0.0", ".v0", true},
+		{"v0.0.0-20190510104115-cbcb75029529", ".v1", true},
+		{"v1.0.0", "/v2", false},
+		{"v1.0.0", ".v1", true},
+		{"v1.0.0", ".v1-unstable", true},
+		{"v2.0.0+incompatible", "", true},
+		{"v2.0.0", "", false},
+		{"v2.0.0", "/v2", true},
+		{"v2.0.0", ".v2", true},
+	} {
+		if got := MatchPathMajor(test.v, test.pathMajor); got != test.want {
+			t.Errorf("MatchPathMajor(%q, %q) = %v, want %v", test.v, test.pathMajor, got, test.want)
+		}
+	}
+}
+
+func TestMatchPrefixPatterns(t *testing.T) {
+	for _, test := range []struct {
+		globs, target string
+		want          bool
+	}{
+		{"", "rsc.io/quote", false},
+		{"/", "rsc.io/quote", false},
+		{"*/quote", "rsc.io/quote", true},
+		{"*/quo", "rsc.io/quote", false},
+		{"*/quo??", "rsc.io/quote", true},
+		{"*/quo*", "rsc.io/quote", true},
+		{"*quo*", "rsc.io/quote", false},
+		{"rsc.io", "rsc.io/quote", true},
+		{"*.io", "rsc.io/quote", true},
+		{"rsc.io/", "rsc.io/quote", true},
+		{"rsc", "rsc.io/quote", false},
+		{"rsc*", "rsc.io/quote", true},
+
+		{"rsc.io", "rsc.io/quote/v3", true},
+		{"*/quote", "rsc.io/quote/v3", true},
+		{"*/quote/", "rsc.io/quote/v3", true},
+		{"*/quote/*", "rsc.io/quote/v3", true},
+		{"*/quote/*/", "rsc.io/quote/v3", true},
+		{"*/v3", "rsc.io/quote/v3", false},
+		{"*/*/v3", "rsc.io/quote/v3", true},
+		{"*/*/*", "rsc.io/quote/v3", true},
+		{"*/*/*/", "rsc.io/quote/v3", true},
+		{"*/*/*", "rsc.io/quote", false},
+		{"*/*/*/", "rsc.io/quote", false},
+
+		{"*/*/*,,", "rsc.io/quote", false},
+		{"*/*/*,,*/quote", "rsc.io/quote", true},
+		{",,*/quote", "rsc.io/quote", true},
+	} {
+		if got := MatchPrefixPatterns(test.globs, test.target); got != test.want {
+			t.Errorf("MatchPrefixPatterns(%q, %q) = %t, want %t", test.globs, test.target, got, test.want)
+		}
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/module/pseudo.go

@@ -0,0 +1,250 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Pseudo-versions
+//
+// Code authors are expected to tag the revisions they want users to use,
+// including prereleases. However, not all authors tag versions at all,
+// and not all commits a user might want to try will have tags.
+// A pseudo-version is a version with a special form that allows us to
+// address an untagged commit and order that version with respect to
+// other versions we might encounter.
+//
+// A pseudo-version takes one of the general forms:
+//
+//	(1) vX.0.0-yyyymmddhhmmss-abcdef123456
+//	(2) vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456
+//	(3) vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456+incompatible
+//	(4) vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456
+//	(5) vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456+incompatible
+//
+// If there is no recently tagged version with the right major version vX,
+// then form (1) is used, creating a space of pseudo-versions at the bottom
+// of the vX version range, less than any tagged version, including the unlikely v0.0.0.
+//
+// If the most recent tagged version before the target commit is vX.Y.Z or vX.Y.Z+incompatible,
+// then the pseudo-version uses form (2) or (3), making it a prerelease for the next
+// possible semantic version after vX.Y.Z. The leading 0 segment in the prerelease string
+// ensures that the pseudo-version compares less than possible future explicit prereleases
+// like vX.Y.(Z+1)-rc1 or vX.Y.(Z+1)-1.
+//
+// If the most recent tagged version before the target commit is vX.Y.Z-pre or vX.Y.Z-pre+incompatible,
+// then the pseudo-version uses form (4) or (5), making it a slightly later prerelease.
+
+package module
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"golang.org/x/mod/internal/lazyregexp"
+	"golang.org/x/mod/semver"
+)
+
+var pseudoVersionRE = lazyregexp.New(`^v[0-9]+\.(0\.0-|\d+\.\d+-([^+]*\.)?0\.)\d{14}-[A-Za-z0-9]+(\+[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$`)
+
+const PseudoVersionTimestampFormat = "20060102150405"
+
+// PseudoVersion returns a pseudo-version for the given major version ("v1")
+// preexisting older tagged version ("" or "v1.2.3" or "v1.2.3-pre"), revision time,
+// and revision identifier (usually a 12-byte commit hash prefix).
+func PseudoVersion(major, older string, t time.Time, rev string) string {
+	if major == "" {
+		major = "v0"
+	}
+	segment := fmt.Sprintf("%s-%s", t.UTC().Format(PseudoVersionTimestampFormat), rev)
+	build := semver.Build(older)
+	older = semver.Canonical(older)
+	if older == "" {
+		return major + ".0.0-" + segment // form (1)
+	}
+	if semver.Prerelease(older) != "" {
+		return older + ".0." + segment + build // form (4), (5)
+	}
+
+	// Form (2), (3).
+	// Extract patch from vMAJOR.MINOR.PATCH
+	i := strings.LastIndex(older, ".") + 1
+	v, patch := older[:i], older[i:]
+
+	// Reassemble.
+	return v + incDecimal(patch) + "-0." + segment + build
+}
+
+// ZeroPseudoVersion returns a pseudo-version with a zero timestamp and
+// revision, which may be used as a placeholder.
+func ZeroPseudoVersion(major string) string {
+	return PseudoVersion(major, "", time.Time{}, "000000000000")
+}
+
+// incDecimal returns the decimal string incremented by 1.
+func incDecimal(decimal string) string {
+	// Scan right to left turning 9s to 0s until you find a digit to increment.
+	digits := []byte(decimal)
+	i := len(digits) - 1
+	for ; i >= 0 && digits[i] == '9'; i-- {
+		digits[i] = '0'
+	}
+	if i >= 0 {
+		digits[i]++
+	} else {
+		// digits is all zeros
+		digits[0] = '1'
+		digits = append(digits, '0')
+	}
+	return string(digits)
+}
+
+// decDecimal returns the decimal string decremented by 1, or the empty string
+// if the decimal is all zeroes.
+func decDecimal(decimal string) string {
+	// Scan right to left turning 0s to 9s until you find a digit to decrement.
+	digits := []byte(decimal)
+	i := len(digits) - 1
+	for ; i >= 0 && digits[i] == '0'; i-- {
+		digits[i] = '9'
+	}
+	if i < 0 {
+		// decimal is all zeros
+		return ""
+	}
+	if i == 0 && digits[i] == '1' && len(digits) > 1 {
+		digits = digits[1:]
+	} else {
+		digits[i]--
+	}
+	return string(digits)
+}
+
+// IsPseudoVersion reports whether v is a pseudo-version.
+func IsPseudoVersion(v string) bool {
+	return strings.Count(v, "-") >= 2 && semver.IsValid(v) && pseudoVersionRE.MatchString(v)
+}
+
+// IsZeroPseudoVersion returns whether v is a pseudo-version with a zero base,
+// timestamp, and revision, as returned by [ZeroPseudoVersion].
+func IsZeroPseudoVersion(v string) bool {
+	return v == ZeroPseudoVersion(semver.Major(v))
+}
+
+// PseudoVersionTime returns the time stamp of the pseudo-version v.
+// It returns an error if v is not a pseudo-version or if the time stamp
+// embedded in the pseudo-version is not a valid time.
+func PseudoVersionTime(v string) (time.Time, error) {
+	_, timestamp, _, _, err := parsePseudoVersion(v)
+	if err != nil {
+		return time.Time{}, err
+	}
+	t, err := time.Parse("20060102150405", timestamp)
+	if err != nil {
+		return time.Time{}, &InvalidVersionError{
+			Version: v,
+			Pseudo:  true,
+			Err:     fmt.Errorf("malformed time %q", timestamp),
+		}
+	}
+	return t, nil
+}
+
+// PseudoVersionRev returns the revision identifier of the pseudo-version v.
+// It returns an error if v is not a pseudo-version.
+func PseudoVersionRev(v string) (rev string, err error) {
+	_, _, rev, _, err = parsePseudoVersion(v)
+	return
+}
+
+// PseudoVersionBase returns the canonical parent version, if any, upon which
+// the pseudo-version v is based.
+//
+// If v has no parent version (that is, if it is "vX.0.0-[…]"),
+// PseudoVersionBase returns the empty string and a nil error.
+func PseudoVersionBase(v string) (string, error) {
+	base, _, _, build, err := parsePseudoVersion(v)
+	if err != nil {
+		return "", err
+	}
+
+	switch pre := semver.Prerelease(base); pre {
+	case "":
+		// vX.0.0-yyyymmddhhmmss-abcdef123456 → ""
+		if build != "" {
+			// Pseudo-versions of the form vX.0.0-yyyymmddhhmmss-abcdef123456+incompatible
+			// are nonsensical: the "vX.0.0-" prefix implies that there is no parent tag,
+			// but the "+incompatible" suffix implies that the major version of
+			// the parent tag is not compatible with the module's import path.
+			//
+			// There are a few such entries in the index generated by proxy.golang.org,
+			// but we believe those entries were generated by the proxy itself.
+			return "", &InvalidVersionError{
+				Version: v,
+				Pseudo:  true,
+				Err:     fmt.Errorf("lacks base version, but has build metadata %q", build),
+			}
+		}
+		return "", nil
+
+	case "-0":
+		// vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456 → vX.Y.Z
+		// vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456+incompatible → vX.Y.Z+incompatible
+		base = strings.TrimSuffix(base, pre)
+		i := strings.LastIndexByte(base, '.')
+		if i < 0 {
+			panic("base from parsePseudoVersion missing patch number: " + base)
+		}
+		patch := decDecimal(base[i+1:])
+		if patch == "" {
+			// vX.0.0-0 is invalid, but has been observed in the wild in the index
+			// generated by requests to proxy.golang.org.
+			//
+			// NOTE(bcmills): I cannot find a historical bug that accounts for
+			// pseudo-versions of this form, nor have I seen such versions in any
+			// actual go.mod files. If we find actual examples of this form and a
+			// reasonable theory of how they came into existence, it seems fine to
+			// treat them as equivalent to vX.0.0 (especially since the invalid
+			// pseudo-versions have lower precedence than the real ones). For now, we
+			// reject them.
+			return "", &InvalidVersionError{
+				Version: v,
+				Pseudo:  true,
+				Err:     fmt.Errorf("version before %s would have negative patch number", base),
+			}
+		}
+		return base[:i+1] + patch + build, nil
+
+	default:
+		// vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456 → vX.Y.Z-pre
+		// vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456+incompatible → vX.Y.Z-pre+incompatible
+		if !strings.HasSuffix(base, ".0") {
+			panic(`base from parsePseudoVersion missing ".0" before date: ` + base)
+		}
+		return strings.TrimSuffix(base, ".0") + build, nil
+	}
+}
+
+var errPseudoSyntax = errors.New("syntax error")
+
+func parsePseudoVersion(v string) (base, timestamp, rev, build string, err error) {
+	if !IsPseudoVersion(v) {
+		return "", "", "", "", &InvalidVersionError{
+			Version: v,
+			Pseudo:  true,
+			Err:     errPseudoSyntax,
+		}
+	}
+	build = semver.Build(v)
+	v = strings.TrimSuffix(v, build)
+	j := strings.LastIndex(v, "-")
+	v, rev = v[:j], v[j+1:]
+	i := strings.LastIndex(v, "-")
+	if j := strings.LastIndex(v, "."); j > i {
+		base = v[:j] // "vX.Y.Z-pre.0" or "vX.Y.(Z+1)-0"
+		timestamp = v[j+1:]
+	} else {
+		base = v[:i] // "vX.0.0"
+		timestamp = v[i+1:]
+	}
+	return base, timestamp, rev, build, nil
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/module/pseudo_test.go

@@ -0,0 +1,154 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package module
+
+import (
+	"testing"
+	"time"
+)
+
+var pseudoTests = []struct {
+	major   string
+	older   string
+	version string
+}{
+	{"", "", "v0.0.0-20060102150405-hash"},
+	{"v0", "", "v0.0.0-20060102150405-hash"},
+	{"v1", "", "v1.0.0-20060102150405-hash"},
+	{"v2", "", "v2.0.0-20060102150405-hash"},
+	{"unused", "v0.0.0", "v0.0.1-0.20060102150405-hash"},
+	{"unused", "v1.2.3", "v1.2.4-0.20060102150405-hash"},
+	{"unused", "v1.2.99999999999999999", "v1.2.100000000000000000-0.20060102150405-hash"},
+	{"unused", "v1.2.3-pre", "v1.2.3-pre.0.20060102150405-hash"},
+	{"unused", "v1.3.0-pre", "v1.3.0-pre.0.20060102150405-hash"},
+	{"unused", "v0.0.0--", "v0.0.0--.0.20060102150405-hash"},
+	{"unused", "v1.0.0+metadata", "v1.0.1-0.20060102150405-hash+metadata"},
+	{"unused", "v2.0.0+incompatible", "v2.0.1-0.20060102150405-hash+incompatible"},
+	{"unused", "v2.3.0-pre+incompatible", "v2.3.0-pre.0.20060102150405-hash+incompatible"},
+}
+
+var pseudoTime = time.Date(2006, 1, 2, 15, 4, 5, 0, time.UTC)
+
+func TestPseudoVersion(t *testing.T) {
+	for _, tt := range pseudoTests {
+		v := PseudoVersion(tt.major, tt.older, pseudoTime, "hash")
+		if v != tt.version {
+			t.Errorf("PseudoVersion(%q, %q, ...) = %v, want %v", tt.major, tt.older, v, tt.version)
+		}
+	}
+}
+
+func TestIsPseudoVersion(t *testing.T) {
+	for _, tt := range pseudoTests {
+		if !IsPseudoVersion(tt.version) {
+			t.Errorf("IsPseudoVersion(%q) = false, want true", tt.version)
+		}
+		if IsPseudoVersion(tt.older) {
+			t.Errorf("IsPseudoVersion(%q) = true, want false", tt.older)
+		}
+	}
+}
+
+func TestPseudoVersionTime(t *testing.T) {
+	for _, tt := range pseudoTests {
+		tm, err := PseudoVersionTime(tt.version)
+		if tm != pseudoTime || err != nil {
+			t.Errorf("PseudoVersionTime(%q) = %v, %v, want %v, nil", tt.version, tm.Format(time.RFC3339), err, pseudoTime.Format(time.RFC3339))
+		}
+		tm, err = PseudoVersionTime(tt.older)
+		if tm != (time.Time{}) || err == nil {
+			t.Errorf("PseudoVersionTime(%q) = %v, %v, want %v, error", tt.older, tm.Format(time.RFC3339), err, time.Time{}.Format(time.RFC3339))
+		}
+	}
+}
+
+func TestInvalidPseudoVersionTime(t *testing.T) {
+	const v = "---"
+	if _, err := PseudoVersionTime(v); err == nil {
+		t.Error("expected error, got nil instead")
+	}
+}
+
+func TestPseudoVersionRev(t *testing.T) {
+	for _, tt := range pseudoTests {
+		rev, err := PseudoVersionRev(tt.version)
+		if rev != "hash" || err != nil {
+			t.Errorf("PseudoVersionRev(%q) = %q, %v, want %q, nil", tt.older, rev, err, "hash")
+		}
+		rev, err = PseudoVersionRev(tt.older)
+		if rev != "" || err == nil {
+			t.Errorf("PseudoVersionRev(%q) = %q, %v, want %q, error", tt.older, rev, err, "")
+		}
+	}
+}
+
+func TestPseudoVersionBase(t *testing.T) {
+	for _, tt := range pseudoTests {
+		base, err := PseudoVersionBase(tt.version)
+		if err != nil {
+			t.Errorf("PseudoVersionBase(%q): %v", tt.version, err)
+		} else if base != tt.older {
+			t.Errorf("PseudoVersionBase(%q) = %q; want %q", tt.version, base, tt.older)
+		}
+	}
+}
+
+func TestInvalidPseudoVersionBase(t *testing.T) {
+	for _, in := range []string{
+		"v0.0.0",
+		"v0.0.0-",                                 // malformed: empty prerelease
+		"v0.0.0-0.20060102150405-hash",            // Z+1 == 0
+		"v0.1.0-0.20060102150405-hash",            // Z+1 == 0
+		"v1.0.0-0.20060102150405-hash",            // Z+1 == 0
+		"v0.0.0-20060102150405-hash+incompatible", // "+incompatible without base version
+		"v0.0.0-20060102150405-hash+metadata",     // other metadata without base version
+	} {
+		base, err := PseudoVersionBase(in)
+		if err == nil || base != "" {
+			t.Errorf(`PseudoVersionBase(%q) = %q, %v; want "", error`, in, base, err)
+		}
+	}
+}
+
+func TestIncDecimal(t *testing.T) {
+	cases := []struct {
+		in, want string
+	}{
+		{"0", "1"},
+		{"1", "2"},
+		{"99", "100"},
+		{"100", "101"},
+		{"101", "102"},
+	}
+
+	for _, tc := range cases {
+		got := incDecimal(tc.in)
+		if got != tc.want {
+			t.Fatalf("incDecimal(%q) = %q; want %q", tc.in, tc.want, got)
+		}
+	}
+}
+
+func TestDecDecimal(t *testing.T) {
+	cases := []struct {
+		in, want string
+	}{
+		{"", ""},
+		{"0", ""},
+		{"00", ""},
+		{"1", "0"},
+		{"2", "1"},
+		{"99", "98"},
+		{"100", "99"},
+		{"101", "100"},
+	}
+
+	for _, tc := range cases {
+		got := decDecimal(tc.in)
+		if got != tc.want {
+			t.Fatalf("decDecimal(%q) = %q; want %q", tc.in, tc.want, got)
+		}
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/semver/semver.go

@@ -0,0 +1,401 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package semver implements comparison of semantic version strings.
+// In this package, semantic version strings must begin with a leading "v",
+// as in "v1.0.0".
+//
+// The general form of a semantic version string accepted by this package is
+//
+//	vMAJOR[.MINOR[.PATCH[-PRERELEASE][+BUILD]]]
+//
+// where square brackets indicate optional parts of the syntax;
+// MAJOR, MINOR, and PATCH are decimal integers without extra leading zeros;
+// PRERELEASE and BUILD are each a series of non-empty dot-separated identifiers
+// using only alphanumeric characters and hyphens; and
+// all-numeric PRERELEASE identifiers must not have leading zeros.
+//
+// This package follows Semantic Versioning 2.0.0 (see semver.org)
+// with two exceptions. First, it requires the "v" prefix. Second, it recognizes
+// vMAJOR and vMAJOR.MINOR (with no prerelease or build suffixes)
+// as shorthands for vMAJOR.0.0 and vMAJOR.MINOR.0.
+package semver
+
+import "sort"
+
+// parsed returns the parsed form of a semantic version string.
+type parsed struct {
+	major      string
+	minor      string
+	patch      string
+	short      string
+	prerelease string
+	build      string
+}
+
+// IsValid reports whether v is a valid semantic version string.
+func IsValid(v string) bool {
+	_, ok := parse(v)
+	return ok
+}
+
+// Canonical returns the canonical formatting of the semantic version v.
+// It fills in any missing .MINOR or .PATCH and discards build metadata.
+// Two semantic versions compare equal only if their canonical formattings
+// are identical strings.
+// The canonical invalid semantic version is the empty string.
+func Canonical(v string) string {
+	p, ok := parse(v)
+	if !ok {
+		return ""
+	}
+	if p.build != "" {
+		return v[:len(v)-len(p.build)]
+	}
+	if p.short != "" {
+		return v + p.short
+	}
+	return v
+}
+
+// Major returns the major version prefix of the semantic version v.
+// For example, Major("v2.1.0") == "v2".
+// If v is an invalid semantic version string, Major returns the empty string.
+func Major(v string) string {
+	pv, ok := parse(v)
+	if !ok {
+		return ""
+	}
+	return v[:1+len(pv.major)]
+}
+
+// MajorMinor returns the major.minor version prefix of the semantic version v.
+// For example, MajorMinor("v2.1.0") == "v2.1".
+// If v is an invalid semantic version string, MajorMinor returns the empty string.
+func MajorMinor(v string) string {
+	pv, ok := parse(v)
+	if !ok {
+		return ""
+	}
+	i := 1 + len(pv.major)
+	if j := i + 1 + len(pv.minor); j <= len(v) && v[i] == '.' && v[i+1:j] == pv.minor {
+		return v[:j]
+	}
+	return v[:i] + "." + pv.minor
+}
+
+// Prerelease returns the prerelease suffix of the semantic version v.
+// For example, Prerelease("v2.1.0-pre+meta") == "-pre".
+// If v is an invalid semantic version string, Prerelease returns the empty string.
+func Prerelease(v string) string {
+	pv, ok := parse(v)
+	if !ok {
+		return ""
+	}
+	return pv.prerelease
+}
+
+// Build returns the build suffix of the semantic version v.
+// For example, Build("v2.1.0+meta") == "+meta".
+// If v is an invalid semantic version string, Build returns the empty string.
+func Build(v string) string {
+	pv, ok := parse(v)
+	if !ok {
+		return ""
+	}
+	return pv.build
+}
+
+// Compare returns an integer comparing two versions according to
+// semantic version precedence.
+// The result will be 0 if v == w, -1 if v < w, or +1 if v > w.
+//
+// An invalid semantic version string is considered less than a valid one.
+// All invalid semantic version strings compare equal to each other.
+func Compare(v, w string) int {
+	pv, ok1 := parse(v)
+	pw, ok2 := parse(w)
+	if !ok1 && !ok2 {
+		return 0
+	}
+	if !ok1 {
+		return -1
+	}
+	if !ok2 {
+		return +1
+	}
+	if c := compareInt(pv.major, pw.major); c != 0 {
+		return c
+	}
+	if c := compareInt(pv.minor, pw.minor); c != 0 {
+		return c
+	}
+	if c := compareInt(pv.patch, pw.patch); c != 0 {
+		return c
+	}
+	return comparePrerelease(pv.prerelease, pw.prerelease)
+}
+
+// Max canonicalizes its arguments and then returns the version string
+// that compares greater.
+//
+// Deprecated: use [Compare] instead. In most cases, returning a canonicalized
+// version is not expected or desired.
+func Max(v, w string) string {
+	v = Canonical(v)
+	w = Canonical(w)
+	if Compare(v, w) > 0 {
+		return v
+	}
+	return w
+}
+
+// ByVersion implements [sort.Interface] for sorting semantic version strings.
+type ByVersion []string
+
+func (vs ByVersion) Len() int      { return len(vs) }
+func (vs ByVersion) Swap(i, j int) { vs[i], vs[j] = vs[j], vs[i] }
+func (vs ByVersion) Less(i, j int) bool {
+	cmp := Compare(vs[i], vs[j])
+	if cmp != 0 {
+		return cmp < 0
+	}
+	return vs[i] < vs[j]
+}
+
+// Sort sorts a list of semantic version strings using [ByVersion].
+func Sort(list []string) {
+	sort.Sort(ByVersion(list))
+}
+
+func parse(v string) (p parsed, ok bool) {
+	if v == "" || v[0] != 'v' {
+		return
+	}
+	p.major, v, ok = parseInt(v[1:])
+	if !ok {
+		return
+	}
+	if v == "" {
+		p.minor = "0"
+		p.patch = "0"
+		p.short = ".0.0"
+		return
+	}
+	if v[0] != '.' {
+		ok = false
+		return
+	}
+	p.minor, v, ok = parseInt(v[1:])
+	if !ok {
+		return
+	}
+	if v == "" {
+		p.patch = "0"
+		p.short = ".0"
+		return
+	}
+	if v[0] != '.' {
+		ok = false
+		return
+	}
+	p.patch, v, ok = parseInt(v[1:])
+	if !ok {
+		return
+	}
+	if len(v) > 0 && v[0] == '-' {
+		p.prerelease, v, ok = parsePrerelease(v)
+		if !ok {
+			return
+		}
+	}
+	if len(v) > 0 && v[0] == '+' {
+		p.build, v, ok = parseBuild(v)
+		if !ok {
+			return
+		}
+	}
+	if v != "" {
+		ok = false
+		return
+	}
+	ok = true
+	return
+}
+
+func parseInt(v string) (t, rest string, ok bool) {
+	if v == "" {
+		return
+	}
+	if v[0] < '0' || '9' < v[0] {
+		return
+	}
+	i := 1
+	for i < len(v) && '0' <= v[i] && v[i] <= '9' {
+		i++
+	}
+	if v[0] == '0' && i != 1 {
+		return
+	}
+	return v[:i], v[i:], true
+}
+
+func parsePrerelease(v string) (t, rest string, ok bool) {
+	// "A pre-release version MAY be denoted by appending a hyphen and
+	// a series of dot separated identifiers immediately following the patch version.
+	// Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-].
+	// Identifiers MUST NOT be empty. Numeric identifiers MUST NOT include leading zeroes."
+	if v == "" || v[0] != '-' {
+		return
+	}
+	i := 1
+	start := 1
+	for i < len(v) && v[i] != '+' {
+		if !isIdentChar(v[i]) && v[i] != '.' {
+			return
+		}
+		if v[i] == '.' {
+			if start == i || isBadNum(v[start:i]) {
+				return
+			}
+			start = i + 1
+		}
+		i++
+	}
+	if start == i || isBadNum(v[start:i]) {
+		return
+	}
+	return v[:i], v[i:], true
+}
+
+func parseBuild(v string) (t, rest string, ok bool) {
+	if v == "" || v[0] != '+' {
+		return
+	}
+	i := 1
+	start := 1
+	for i < len(v) {
+		if !isIdentChar(v[i]) && v[i] != '.' {
+			return
+		}
+		if v[i] == '.' {
+			if start == i {
+				return
+			}
+			start = i + 1
+		}
+		i++
+	}
+	if start == i {
+		return
+	}
+	return v[:i], v[i:], true
+}
+
+func isIdentChar(c byte) bool {
+	return 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || '0' <= c && c <= '9' || c == '-'
+}
+
+func isBadNum(v string) bool {
+	i := 0
+	for i < len(v) && '0' <= v[i] && v[i] <= '9' {
+		i++
+	}
+	return i == len(v) && i > 1 && v[0] == '0'
+}
+
+func isNum(v string) bool {
+	i := 0
+	for i < len(v) && '0' <= v[i] && v[i] <= '9' {
+		i++
+	}
+	return i == len(v)
+}
+
+func compareInt(x, y string) int {
+	if x == y {
+		return 0
+	}
+	if len(x) < len(y) {
+		return -1
+	}
+	if len(x) > len(y) {
+		return +1
+	}
+	if x < y {
+		return -1
+	} else {
+		return +1
+	}
+}
+
+func comparePrerelease(x, y string) int {
+	// "When major, minor, and patch are equal, a pre-release version has
+	// lower precedence than a normal version.
+	// Example: 1.0.0-alpha < 1.0.0.
+	// Precedence for two pre-release versions with the same major, minor,
+	// and patch version MUST be determined by comparing each dot separated
+	// identifier from left to right until a difference is found as follows:
+	// identifiers consisting of only digits are compared numerically and
+	// identifiers with letters or hyphens are compared lexically in ASCII
+	// sort order. Numeric identifiers always have lower precedence than
+	// non-numeric identifiers. A larger set of pre-release fields has a
+	// higher precedence than a smaller set, if all of the preceding
+	// identifiers are equal.
+	// Example: 1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-alpha.beta <
+	// 1.0.0-beta < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0."
+	if x == y {
+		return 0
+	}
+	if x == "" {
+		return +1
+	}
+	if y == "" {
+		return -1
+	}
+	for x != "" && y != "" {
+		x = x[1:] // skip - or .
+		y = y[1:] // skip - or .
+		var dx, dy string
+		dx, x = nextIdent(x)
+		dy, y = nextIdent(y)
+		if dx != dy {
+			ix := isNum(dx)
+			iy := isNum(dy)
+			if ix != iy {
+				if ix {
+					return -1
+				} else {
+					return +1
+				}
+			}
+			if ix {
+				if len(dx) < len(dy) {
+					return -1
+				}
+				if len(dx) > len(dy) {
+					return +1
+				}
+			}
+			if dx < dy {
+				return -1
+			} else {
+				return +1
+			}
+		}
+	}
+	if x == "" {
+		return -1
+	} else {
+		return +1
+	}
+}
+
+func nextIdent(x string) (dx, rest string) {
+	i := 0
+	for i < len(x) && x[i] != '.' {
+		i++
+	}
+	return x[:i], x[i:]
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/semver/semver_test.go

@@ -0,0 +1,197 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package semver
+
+import (
+	"math/rand"
+	"sort"
+	"strings"
+	"testing"
+)
+
+var tests = []struct {
+	in  string
+	out string
+}{
+	{"bad", ""},
+	{"v1-alpha.beta.gamma", ""},
+	{"v1-pre", ""},
+	{"v1+meta", ""},
+	{"v1-pre+meta", ""},
+	{"v1.2-pre", ""},
+	{"v1.2+meta", ""},
+	{"v1.2-pre+meta", ""},
+	{"v1.0.0-alpha", "v1.0.0-alpha"},
+	{"v1.0.0-alpha.1", "v1.0.0-alpha.1"},
+	{"v1.0.0-alpha.beta", "v1.0.0-alpha.beta"},
+	{"v1.0.0-beta", "v1.0.0-beta"},
+	{"v1.0.0-beta.2", "v1.0.0-beta.2"},
+	{"v1.0.0-beta.11", "v1.0.0-beta.11"},
+	{"v1.0.0-rc.1", "v1.0.0-rc.1"},
+	{"v1", "v1.0.0"},
+	{"v1.0", "v1.0.0"},
+	{"v1.0.0", "v1.0.0"},
+	{"v1.2", "v1.2.0"},
+	{"v1.2.0", "v1.2.0"},
+	{"v1.2.3-456", "v1.2.3-456"},
+	{"v1.2.3-456.789", "v1.2.3-456.789"},
+	{"v1.2.3-456-789", "v1.2.3-456-789"},
+	{"v1.2.3-456a", "v1.2.3-456a"},
+	{"v1.2.3-pre", "v1.2.3-pre"},
+	{"v1.2.3-pre+meta", "v1.2.3-pre"},
+	{"v1.2.3-pre.1", "v1.2.3-pre.1"},
+	{"v1.2.3-zzz", "v1.2.3-zzz"},
+	{"v1.2.3", "v1.2.3"},
+	{"v1.2.3+meta", "v1.2.3"},
+	{"v1.2.3+meta-pre", "v1.2.3"},
+	{"v1.2.3+meta-pre.sha.256a", "v1.2.3"},
+}
+
+func TestIsValid(t *testing.T) {
+	for _, tt := range tests {
+		ok := IsValid(tt.in)
+		if ok != (tt.out != "") {
+			t.Errorf("IsValid(%q) = %v, want %v", tt.in, ok, !ok)
+		}
+	}
+}
+
+func TestCanonical(t *testing.T) {
+	for _, tt := range tests {
+		out := Canonical(tt.in)
+		if out != tt.out {
+			t.Errorf("Canonical(%q) = %q, want %q", tt.in, out, tt.out)
+		}
+	}
+}
+
+func TestMajor(t *testing.T) {
+	for _, tt := range tests {
+		out := Major(tt.in)
+		want := ""
+		if i := strings.Index(tt.out, "."); i >= 0 {
+			want = tt.out[:i]
+		}
+		if out != want {
+			t.Errorf("Major(%q) = %q, want %q", tt.in, out, want)
+		}
+	}
+}
+
+func TestMajorMinor(t *testing.T) {
+	for _, tt := range tests {
+		out := MajorMinor(tt.in)
+		var want string
+		if tt.out != "" {
+			want = tt.in
+			if i := strings.Index(want, "+"); i >= 0 {
+				want = want[:i]
+			}
+			if i := strings.Index(want, "-"); i >= 0 {
+				want = want[:i]
+			}
+			switch strings.Count(want, ".") {
+			case 0:
+				want += ".0"
+			case 1:
+				// ok
+			case 2:
+				want = want[:strings.LastIndex(want, ".")]
+			}
+		}
+		if out != want {
+			t.Errorf("MajorMinor(%q) = %q, want %q", tt.in, out, want)
+		}
+	}
+}
+
+func TestPrerelease(t *testing.T) {
+	for _, tt := range tests {
+		pre := Prerelease(tt.in)
+		var want string
+		if tt.out != "" {
+			if i := strings.Index(tt.out, "-"); i >= 0 {
+				want = tt.out[i:]
+			}
+		}
+		if pre != want {
+			t.Errorf("Prerelease(%q) = %q, want %q", tt.in, pre, want)
+		}
+	}
+}
+
+func TestBuild(t *testing.T) {
+	for _, tt := range tests {
+		build := Build(tt.in)
+		var want string
+		if tt.out != "" {
+			if i := strings.Index(tt.in, "+"); i >= 0 {
+				want = tt.in[i:]
+			}
+		}
+		if build != want {
+			t.Errorf("Build(%q) = %q, want %q", tt.in, build, want)
+		}
+	}
+}
+
+func TestCompare(t *testing.T) {
+	for i, ti := range tests {
+		for j, tj := range tests {
+			cmp := Compare(ti.in, tj.in)
+			var want int
+			if ti.out == tj.out {
+				want = 0
+			} else if i < j {
+				want = -1
+			} else {
+				want = +1
+			}
+			if cmp != want {
+				t.Errorf("Compare(%q, %q) = %d, want %d", ti.in, tj.in, cmp, want)
+			}
+		}
+	}
+}
+
+func TestSort(t *testing.T) {
+	versions := make([]string, len(tests))
+	for i, test := range tests {
+		versions[i] = test.in
+	}
+	rand.Shuffle(len(versions), func(i, j int) { versions[i], versions[j] = versions[j], versions[i] })
+	Sort(versions)
+	if !sort.IsSorted(ByVersion(versions)) {
+		t.Errorf("list is not sorted:\n%s", strings.Join(versions, "\n"))
+	}
+}
+
+func TestMax(t *testing.T) {
+	for i, ti := range tests {
+		for j, tj := range tests {
+			max := Max(ti.in, tj.in)
+			want := Canonical(ti.in)
+			if i < j {
+				want = Canonical(tj.in)
+			}
+			if max != want {
+				t.Errorf("Max(%q, %q) = %q, want %q", ti.in, tj.in, max, want)
+			}
+		}
+	}
+}
+
+var (
+	v1 = "v1.0.0+metadata-dash"
+	v2 = "v1.0.0+metadata-dash1"
+)
+
+func BenchmarkCompare(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if Compare(v1, v2) != 0 {
+			b.Fatalf("bad compare")
+		}
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/cache.go

@@ -0,0 +1,59 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parallel cache.
+// This file is copied from cmd/go/internal/par.
+
+package sumdb
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// parCache runs an action once per key and caches the result.
+type parCache struct {
+	m sync.Map
+}
+
+type cacheEntry struct {
+	done   uint32
+	mu     sync.Mutex
+	result interface{}
+}
+
+// Do calls the function f if and only if Do is being called for the first time with this key.
+// No call to Do with a given key returns until the one call to f returns.
+// Do returns the value returned by the one call to f.
+func (c *parCache) Do(key interface{}, f func() interface{}) interface{} {
+	entryIface, ok := c.m.Load(key)
+	if !ok {
+		entryIface, _ = c.m.LoadOrStore(key, new(cacheEntry))
+	}
+	e := entryIface.(*cacheEntry)
+	if atomic.LoadUint32(&e.done) == 0 {
+		e.mu.Lock()
+		if atomic.LoadUint32(&e.done) == 0 {
+			e.result = f()
+			atomic.StoreUint32(&e.done, 1)
+		}
+		e.mu.Unlock()
+	}
+	return e.result
+}
+
+// Get returns the cached result associated with key.
+// It returns nil if there is no such result.
+// If the result for key is being computed, Get does not wait for the computation to finish.
+func (c *parCache) Get(key interface{}) interface{} {
+	entryIface, ok := c.m.Load(key)
+	if !ok {
+		return nil
+	}
+	e := entryIface.(*cacheEntry)
+	if atomic.LoadUint32(&e.done) == 0 {
+		return nil
+	}
+	return e.result
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/client.go

@@ -0,0 +1,676 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sumdb
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"path"
+	"strings"
+	"sync"
+	"sync/atomic"
+
+	"golang.org/x/mod/module"
+	"golang.org/x/mod/sumdb/note"
+	"golang.org/x/mod/sumdb/tlog"
+)
+
+// A ClientOps provides the external operations
+// (file caching, HTTP fetches, and so on) needed by the [Client].
+// The methods must be safe for concurrent use by multiple goroutines.
+type ClientOps interface {
+	// ReadRemote reads and returns the content served at the given path
+	// on the remote database server. The path begins with "/lookup" or "/tile/",
+	// and there is no need to parse the path in any way.
+	// It is the implementation's responsibility to turn that path into a full URL
+	// and make the HTTP request. ReadRemote should return an error for
+	// any non-200 HTTP response status.
+	ReadRemote(path string) ([]byte, error)
+
+	// ReadConfig reads and returns the content of the named configuration file.
+	// There are only a fixed set of configuration files.
+	//
+	// "key" returns a file containing the verifier key for the server.
+	//
+	// serverName + "/latest" returns a file containing the latest known
+	// signed tree from the server.
+	// To signal that the client wishes to start with an "empty" signed tree,
+	// ReadConfig can return a successful empty result (0 bytes of data).
+	ReadConfig(file string) ([]byte, error)
+
+	// WriteConfig updates the content of the named configuration file,
+	// changing it from the old []byte to the new []byte.
+	// If the old []byte does not match the stored configuration,
+	// WriteConfig must return ErrWriteConflict.
+	// Otherwise, WriteConfig should atomically replace old with new.
+	// The "key" configuration file is never written using WriteConfig.
+	WriteConfig(file string, old, new []byte) error
+
+	// ReadCache reads and returns the content of the named cache file.
+	// Any returned error will be treated as equivalent to the file not existing.
+	// There can be arbitrarily many cache files, such as:
+	//	serverName/lookup/pkg@version
+	//	serverName/tile/8/1/x123/456
+	ReadCache(file string) ([]byte, error)
+
+	// WriteCache writes the named cache file.
+	WriteCache(file string, data []byte)
+
+	// Log prints the given log message (such as with log.Print)
+	Log(msg string)
+
+	// SecurityError prints the given security error log message.
+	// The Client returns ErrSecurity from any operation that invokes SecurityError,
+	// but the return value is mainly for testing. In a real program,
+	// SecurityError should typically print the message and call log.Fatal or os.Exit.
+	SecurityError(msg string)
+}
+
+// ErrWriteConflict signals a write conflict during Client.WriteConfig.
+var ErrWriteConflict = errors.New("write conflict")
+
+// ErrSecurity is returned by [Client] operations that invoke Client.SecurityError.
+var ErrSecurity = errors.New("security error: misbehaving server")
+
+// A Client is a client connection to a checksum database.
+// All the methods are safe for simultaneous use by multiple goroutines.
+type Client struct {
+	ops ClientOps // access to operations in the external world
+
+	didLookup uint32
+
+	// one-time initialized data
+	initOnce   sync.Once
+	initErr    error          // init error, if any
+	name       string         // name of accepted verifier
+	verifiers  note.Verifiers // accepted verifiers (just one, but Verifiers for note.Open)
+	tileReader tileReader
+	tileHeight int
+	nosumdb    string
+
+	record    parCache // cache of record lookup, keyed by path@vers
+	tileCache parCache // cache of c.readTile, keyed by tile
+
+	latestMu  sync.Mutex
+	latest    tlog.Tree // latest known tree head
+	latestMsg []byte    // encoded signed note for latest
+
+	tileSavedMu sync.Mutex
+	tileSaved   map[tlog.Tile]bool // which tiles have been saved using c.ops.WriteCache already
+}
+
+// NewClient returns a new [Client] using the given [ClientOps].
+func NewClient(ops ClientOps) *Client {
+	return &Client{
+		ops: ops,
+	}
+}
+
+// init initializes the client (if not already initialized)
+// and returns any initialization error.
+func (c *Client) init() error {
+	c.initOnce.Do(c.initWork)
+	return c.initErr
+}
+
+// initWork does the actual initialization work.
+func (c *Client) initWork() {
+	defer func() {
+		if c.initErr != nil {
+			c.initErr = fmt.Errorf("initializing sumdb.Client: %v", c.initErr)
+		}
+	}()
+
+	c.tileReader.c = c
+	if c.tileHeight == 0 {
+		c.tileHeight = 8
+	}
+	c.tileSaved = make(map[tlog.Tile]bool)
+
+	vkey, err := c.ops.ReadConfig("key")
+	if err != nil {
+		c.initErr = err
+		return
+	}
+	verifier, err := note.NewVerifier(strings.TrimSpace(string(vkey)))
+	if err != nil {
+		c.initErr = err
+		return
+	}
+	c.verifiers = note.VerifierList(verifier)
+	c.name = verifier.Name()
+
+	data, err := c.ops.ReadConfig(c.name + "/latest")
+	if err != nil {
+		c.initErr = err
+		return
+	}
+	if err := c.mergeLatest(data); err != nil {
+		c.initErr = err
+		return
+	}
+}
+
+// SetTileHeight sets the tile height for the Client.
+// Any call to SetTileHeight must happen before the first call to [Client.Lookup].
+// If SetTileHeight is not called, the Client defaults to tile height 8.
+// SetTileHeight can be called at most once,
+// and if so it must be called before the first call to Lookup.
+func (c *Client) SetTileHeight(height int) {
+	if atomic.LoadUint32(&c.didLookup) != 0 {
+		panic("SetTileHeight used after Lookup")
+	}
+	if height <= 0 {
+		panic("invalid call to SetTileHeight")
+	}
+	if c.tileHeight != 0 {
+		panic("multiple calls to SetTileHeight")
+	}
+	c.tileHeight = height
+}
+
+// SetGONOSUMDB sets the list of comma-separated GONOSUMDB patterns for the Client.
+// For any module path matching one of the patterns,
+// [Client.Lookup] will return ErrGONOSUMDB.
+// SetGONOSUMDB can be called at most once,
+// and if so it must be called before the first call to Lookup.
+func (c *Client) SetGONOSUMDB(list string) {
+	if atomic.LoadUint32(&c.didLookup) != 0 {
+		panic("SetGONOSUMDB used after Lookup")
+	}
+	if c.nosumdb != "" {
+		panic("multiple calls to SetGONOSUMDB")
+	}
+	c.nosumdb = list
+}
+
+// ErrGONOSUMDB is returned by [Client.Lookup] for paths that match
+// a pattern listed in the GONOSUMDB list (set by [Client.SetGONOSUMDB],
+// usually from the environment variable).
+var ErrGONOSUMDB = errors.New("skipped (listed in GONOSUMDB)")
+
+func (c *Client) skip(target string) bool {
+	return globsMatchPath(c.nosumdb, target)
+}
+
+// globsMatchPath reports whether any path prefix of target
+// matches one of the glob patterns (as defined by path.Match)
+// in the comma-separated globs list.
+// It ignores any empty or malformed patterns in the list.
+func globsMatchPath(globs, target string) bool {
+	for globs != "" {
+		// Extract next non-empty glob in comma-separated list.
+		var glob string
+		if i := strings.Index(globs, ","); i >= 0 {
+			glob, globs = globs[:i], globs[i+1:]
+		} else {
+			glob, globs = globs, ""
+		}
+		if glob == "" {
+			continue
+		}
+
+		// A glob with N+1 path elements (N slashes) needs to be matched
+		// against the first N+1 path elements of target,
+		// which end just before the N+1'th slash.
+		n := strings.Count(glob, "/")
+		prefix := target
+		// Walk target, counting slashes, truncating at the N+1'th slash.
+		for i := 0; i < len(target); i++ {
+			if target[i] == '/' {
+				if n == 0 {
+					prefix = target[:i]
+					break
+				}
+				n--
+			}
+		}
+		if n > 0 {
+			// Not enough prefix elements.
+			continue
+		}
+		matched, _ := path.Match(glob, prefix)
+		if matched {
+			return true
+		}
+	}
+	return false
+}
+
+// Lookup returns the go.sum lines for the given module path and version.
+// The version may end in a /go.mod suffix, in which case Lookup returns
+// the go.sum lines for the module's go.mod-only hash.
+func (c *Client) Lookup(path, vers string) (lines []string, err error) {
+	atomic.StoreUint32(&c.didLookup, 1)
+
+	if c.skip(path) {
+		return nil, ErrGONOSUMDB
+	}
+
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("%s@%s: %v", path, vers, err)
+		}
+	}()
+
+	if err := c.init(); err != nil {
+		return nil, err
+	}
+
+	// Prepare encoded cache filename / URL.
+	epath, err := module.EscapePath(path)
+	if err != nil {
+		return nil, err
+	}
+	evers, err := module.EscapeVersion(strings.TrimSuffix(vers, "/go.mod"))
+	if err != nil {
+		return nil, err
+	}
+	remotePath := "/lookup/" + epath + "@" + evers
+	file := c.name + remotePath
+
+	// Fetch the data.
+	// The lookupCache avoids redundant ReadCache/GetURL operations
+	// (especially since go.sum lines tend to come in pairs for a given
+	// path and version) and also avoids having multiple of the same
+	// request in flight at once.
+	type cached struct {
+		data []byte
+		err  error
+	}
+	result := c.record.Do(file, func() interface{} {
+		// Try the on-disk cache, or else get from web.
+		writeCache := false
+		data, err := c.ops.ReadCache(file)
+		if err != nil {
+			data, err = c.ops.ReadRemote(remotePath)
+			if err != nil {
+				return cached{nil, err}
+			}
+			writeCache = true
+		}
+
+		// Validate the record before using it for anything.
+		id, text, treeMsg, err := tlog.ParseRecord(data)
+		if err != nil {
+			return cached{nil, err}
+		}
+		if err := c.mergeLatest(treeMsg); err != nil {
+			return cached{nil, err}
+		}
+		if err := c.checkRecord(id, text); err != nil {
+			return cached{nil, err}
+		}
+
+		// Now that we've validated the record,
+		// save it to the on-disk cache (unless that's where it came from).
+		if writeCache {
+			c.ops.WriteCache(file, data)
+		}
+
+		return cached{data, nil}
+	}).(cached)
+	if result.err != nil {
+		return nil, result.err
+	}
+
+	// Extract the lines for the specific version we want
+	// (with or without /go.mod).
+	prefix := path + " " + vers + " "
+	var hashes []string
+	for _, line := range strings.Split(string(result.data), "\n") {
+		if strings.HasPrefix(line, prefix) {
+			hashes = append(hashes, line)
+		}
+	}
+	return hashes, nil
+}
+
+// mergeLatest merges the tree head in msg
+// with the Client's current latest tree head,
+// ensuring the result is a consistent timeline.
+// If the result is inconsistent, mergeLatest calls c.ops.SecurityError
+// with a detailed security error message and then
+// (only if c.ops.SecurityError does not exit the program) returns ErrSecurity.
+// If the Client's current latest tree head moves forward,
+// mergeLatest updates the underlying configuration file as well,
+// taking care to merge any independent updates to that configuration.
+func (c *Client) mergeLatest(msg []byte) error {
+	// Merge msg into our in-memory copy of the latest tree head.
+	when, err := c.mergeLatestMem(msg)
+	if err != nil {
+		return err
+	}
+	if when != msgFuture {
+		// msg matched our present or was in the past.
+		// No change to our present, so no update of config file.
+		return nil
+	}
+
+	// Flush our extended timeline back out to the configuration file.
+	// If the configuration file has been updated in the interim,
+	// we need to merge any updates made there as well.
+	// Note that writeConfig is an atomic compare-and-swap.
+	for {
+		msg, err := c.ops.ReadConfig(c.name + "/latest")
+		if err != nil {
+			return err
+		}
+		when, err := c.mergeLatestMem(msg)
+		if err != nil {
+			return err
+		}
+		if when != msgPast {
+			// msg matched our present or was from the future,
+			// and now our in-memory copy matches.
+			return nil
+		}
+
+		// msg (== config) is in the past, so we need to update it.
+		c.latestMu.Lock()
+		latestMsg := c.latestMsg
+		c.latestMu.Unlock()
+		if err := c.ops.WriteConfig(c.name+"/latest", msg, latestMsg); err != ErrWriteConflict {
+			// Success or a non-write-conflict error.
+			return err
+		}
+	}
+}
+
+const (
+	msgPast = 1 + iota
+	msgNow
+	msgFuture
+)
+
+// mergeLatestMem is like mergeLatest but is only concerned with
+// updating the in-memory copy of the latest tree head (c.latest)
+// not the configuration file.
+// The when result explains when msg happened relative to our
+// previous idea of c.latest:
+// msgPast means msg was from before c.latest,
+// msgNow means msg was exactly c.latest, and
+// msgFuture means msg was from after c.latest, which has now been updated.
+func (c *Client) mergeLatestMem(msg []byte) (when int, err error) {
+	if len(msg) == 0 {
+		// Accept empty msg as the unsigned, empty timeline.
+		c.latestMu.Lock()
+		latest := c.latest
+		c.latestMu.Unlock()
+		if latest.N == 0 {
+			return msgNow, nil
+		}
+		return msgPast, nil
+	}
+
+	note, err := note.Open(msg, c.verifiers)
+	if err != nil {
+		return 0, fmt.Errorf("reading tree note: %v\nnote:\n%s", err, msg)
+	}
+	tree, err := tlog.ParseTree([]byte(note.Text))
+	if err != nil {
+		return 0, fmt.Errorf("reading tree: %v\ntree:\n%s", err, note.Text)
+	}
+
+	// Other lookups may be calling mergeLatest with other heads,
+	// so c.latest is changing underfoot. We don't want to hold the
+	// c.mu lock during tile fetches, so loop trying to update c.latest.
+	c.latestMu.Lock()
+	latest := c.latest
+	latestMsg := c.latestMsg
+	c.latestMu.Unlock()
+
+	for {
+		// If the tree head looks old, check that it is on our timeline.
+		if tree.N <= latest.N {
+			if err := c.checkTrees(tree, msg, latest, latestMsg); err != nil {
+				return 0, err
+			}
+			if tree.N < latest.N {
+				return msgPast, nil
+			}
+			return msgNow, nil
+		}
+
+		// The tree head looks new. Check that we are on its timeline and try to move our timeline forward.
+		if err := c.checkTrees(latest, latestMsg, tree, msg); err != nil {
+			return 0, err
+		}
+
+		// Install our msg if possible.
+		// Otherwise we will go around again.
+		c.latestMu.Lock()
+		installed := false
+		if c.latest == latest {
+			installed = true
+			c.latest = tree
+			c.latestMsg = msg
+		} else {
+			latest = c.latest
+			latestMsg = c.latestMsg
+		}
+		c.latestMu.Unlock()
+
+		if installed {
+			return msgFuture, nil
+		}
+	}
+}
+
+// checkTrees checks that older (from olderNote) is contained in newer (from newerNote).
+// If an error occurs, such as malformed data or a network problem, checkTrees returns that error.
+// If on the other hand checkTrees finds evidence of misbehavior, it prepares a detailed
+// message and calls log.Fatal.
+func (c *Client) checkTrees(older tlog.Tree, olderNote []byte, newer tlog.Tree, newerNote []byte) error {
+	thr := tlog.TileHashReader(newer, &c.tileReader)
+	h, err := tlog.TreeHash(older.N, thr)
+	if err != nil {
+		if older.N == newer.N {
+			return fmt.Errorf("checking tree#%d: %v", older.N, err)
+		}
+		return fmt.Errorf("checking tree#%d against tree#%d: %v", older.N, newer.N, err)
+	}
+	if h == older.Hash {
+		return nil
+	}
+
+	// Detected a fork in the tree timeline.
+	// Start by reporting the inconsistent signed tree notes.
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, "SECURITY ERROR\n")
+	fmt.Fprintf(&buf, "go.sum database server misbehavior detected!\n\n")
+	indent := func(b []byte) []byte {
+		return bytes.Replace(b, []byte("\n"), []byte("\n\t"), -1)
+	}
+	fmt.Fprintf(&buf, "old database:\n\t%s\n", indent(olderNote))
+	fmt.Fprintf(&buf, "new database:\n\t%s\n", indent(newerNote))
+
+	// The notes alone are not enough to prove the inconsistency.
+	// We also need to show that the newer note's tree hash for older.N
+	// does not match older.Hash. The consumer of this report could
+	// of course consult the server to try to verify the inconsistency,
+	// but we are holding all the bits we need to prove it right now,
+	// so we might as well print them and make the report not depend
+	// on the continued availability of the misbehaving server.
+	// Preparing this data only reuses the tiled hashes needed for
+	// tlog.TreeHash(older.N, thr) above, so assuming thr is caching tiles,
+	// there are no new access to the server here, and these operations cannot fail.
+	fmt.Fprintf(&buf, "proof of misbehavior:\n\t%v", h)
+	if p, err := tlog.ProveTree(newer.N, older.N, thr); err != nil {
+		fmt.Fprintf(&buf, "\tinternal error: %v\n", err)
+	} else if err := tlog.CheckTree(p, newer.N, newer.Hash, older.N, h); err != nil {
+		fmt.Fprintf(&buf, "\tinternal error: generated inconsistent proof\n")
+	} else {
+		for _, h := range p {
+			fmt.Fprintf(&buf, "\n\t%v", h)
+		}
+	}
+	c.ops.SecurityError(buf.String())
+	return ErrSecurity
+}
+
+// checkRecord checks that record #id's hash matches data.
+func (c *Client) checkRecord(id int64, data []byte) error {
+	c.latestMu.Lock()
+	latest := c.latest
+	c.latestMu.Unlock()
+
+	if id >= latest.N {
+		return fmt.Errorf("cannot validate record %d in tree of size %d", id, latest.N)
+	}
+	hashes, err := tlog.TileHashReader(latest, &c.tileReader).ReadHashes([]int64{tlog.StoredHashIndex(0, id)})
+	if err != nil {
+		return err
+	}
+	if hashes[0] == tlog.RecordHash(data) {
+		return nil
+	}
+	return fmt.Errorf("cannot authenticate record data in server response")
+}
+
+// tileReader is a *Client wrapper that implements tlog.TileReader.
+// The separate type avoids exposing the ReadTiles and SaveTiles
+// methods on Client itself.
+type tileReader struct {
+	c *Client
+}
+
+func (r *tileReader) Height() int {
+	return r.c.tileHeight
+}
+
+// ReadTiles reads and returns the requested tiles,
+// either from the on-disk cache or the server.
+func (r *tileReader) ReadTiles(tiles []tlog.Tile) ([][]byte, error) {
+	// Read all the tiles in parallel.
+	data := make([][]byte, len(tiles))
+	errs := make([]error, len(tiles))
+	var wg sync.WaitGroup
+	for i, tile := range tiles {
+		wg.Add(1)
+		go func(i int, tile tlog.Tile) {
+			defer wg.Done()
+			defer func() {
+				if e := recover(); e != nil {
+					errs[i] = fmt.Errorf("panic: %v", e)
+				}
+			}()
+			data[i], errs[i] = r.c.readTile(tile)
+		}(i, tile)
+	}
+	wg.Wait()
+
+	for _, err := range errs {
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return data, nil
+}
+
+// tileCacheKey returns the cache key for the tile.
+func (c *Client) tileCacheKey(tile tlog.Tile) string {
+	return c.name + "/" + tile.Path()
+}
+
+// tileRemotePath returns the remote path for the tile.
+func (c *Client) tileRemotePath(tile tlog.Tile) string {
+	return "/" + tile.Path()
+}
+
+// readTile reads a single tile, either from the on-disk cache or the server.
+func (c *Client) readTile(tile tlog.Tile) ([]byte, error) {
+	type cached struct {
+		data []byte
+		err  error
+	}
+
+	result := c.tileCache.Do(tile, func() interface{} {
+		// Try the requested tile in on-disk cache.
+		data, err := c.ops.ReadCache(c.tileCacheKey(tile))
+		if err == nil {
+			c.markTileSaved(tile)
+			return cached{data, nil}
+		}
+
+		// Try the full tile in on-disk cache (if requested tile not already full).
+		// We only save authenticated tiles to the on-disk cache,
+		// so the recreated prefix is equally authenticated.
+		full := tile
+		full.W = 1 << uint(tile.H)
+		if tile != full {
+			data, err := c.ops.ReadCache(c.tileCacheKey(full))
+			if err == nil {
+				c.markTileSaved(tile) // don't save tile later; we already have full
+				return cached{data[:len(data)/full.W*tile.W], nil}
+			}
+		}
+
+		// Try requested tile from server.
+		data, err = c.ops.ReadRemote(c.tileRemotePath(tile))
+		if err == nil {
+			return cached{data, nil}
+		}
+
+		// Try full tile on server.
+		// If the partial tile does not exist, it should be because
+		// the tile has been completed and only the complete one
+		// is available.
+		if tile != full {
+			data, err := c.ops.ReadRemote(c.tileRemotePath(full))
+			if err == nil {
+				// Note: We could save the full tile in the on-disk cache here,
+				// but we don't know if it is valid yet, and we will only find out
+				// about the partial data, not the full data. So let SaveTiles
+				// save the partial tile, and we'll just refetch the full tile later
+				// once we can validate more (or all) of it.
+				return cached{data[:len(data)/full.W*tile.W], nil}
+			}
+		}
+
+		// Nothing worked.
+		// Return the error from the server fetch for the requested (not full) tile.
+		return cached{nil, err}
+	}).(cached)
+
+	return result.data, result.err
+}
+
+// markTileSaved records that tile is already present in the on-disk cache,
+// so that a future SaveTiles for that tile can be ignored.
+func (c *Client) markTileSaved(tile tlog.Tile) {
+	c.tileSavedMu.Lock()
+	c.tileSaved[tile] = true
+	c.tileSavedMu.Unlock()
+}
+
+// SaveTiles saves the now validated tiles.
+func (r *tileReader) SaveTiles(tiles []tlog.Tile, data [][]byte) {
+	c := r.c
+
+	// Determine which tiles need saving.
+	// (Tiles that came from the cache need not be saved back.)
+	save := make([]bool, len(tiles))
+	c.tileSavedMu.Lock()
+	for i, tile := range tiles {
+		if !c.tileSaved[tile] {
+			save[i] = true
+			c.tileSaved[tile] = true
+		}
+	}
+	c.tileSavedMu.Unlock()
+
+	for i, tile := range tiles {
+		if save[i] {
+			// If WriteCache fails here (out of disk space? i/o error?),
+			// c.tileSaved[tile] is still true and we will not try to write it again.
+			// Next time we run maybe we'll redownload it again and be
+			// more successful.
+			c.ops.WriteCache(c.name+"/"+tile.Path(), data[i])
+		}
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/client_test.go

@@ -0,0 +1,460 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sumdb
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"sync"
+	"testing"
+
+	"golang.org/x/mod/sumdb/note"
+	"golang.org/x/mod/sumdb/tlog"
+)
+
+const (
+	testName        = "localhost.localdev/sumdb"
+	testVerifierKey = "localhost.localdev/sumdb+00000c67+AcTrnkbUA+TU4heY3hkjiSES/DSQniBqIeQ/YppAUtK6"
+	testSignerKey   = "PRIVATE+KEY+localhost.localdev/sumdb+00000c67+AXu6+oaVaOYuQOFrf1V59JK1owcFlJcHwwXHDfDGxSPk"
+)
+
+func TestClientLookup(t *testing.T) {
+	tc := newTestClient(t)
+	tc.mustHaveLatest(1)
+
+	// Basic lookup.
+	tc.mustLookup("rsc.io/sampler", "v1.3.0", "rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=")
+	tc.mustHaveLatest(3)
+
+	// Everything should now be cached, both for the original package and its /go.mod.
+	tc.getOK = false
+	tc.mustLookup("rsc.io/sampler", "v1.3.0", "rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=")
+	tc.mustLookup("rsc.io/sampler", "v1.3.0/go.mod", "rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=")
+	tc.mustHaveLatest(3)
+	tc.getOK = true
+	tc.getTileOK = false // the cache has what we need
+
+	// Lookup with multiple returned lines.
+	tc.mustLookup("rsc.io/quote", "v1.5.2", "rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=\nrsc.io/quote v1.5.2 h2:xyzzy")
+	tc.mustHaveLatest(3)
+
+	// Lookup with need for !-encoding.
+	// rsc.io/Quote is the only record written after rsc.io/samper,
+	// so it is the only one that should need more tiles.
+	tc.getTileOK = true
+	tc.mustLookup("rsc.io/Quote", "v1.5.2", "rsc.io/Quote v1.5.2 h1:uppercase!=")
+	tc.mustHaveLatest(4)
+}
+
+func TestClientBadTiles(t *testing.T) {
+	tc := newTestClient(t)
+
+	flipBits := func() {
+		for url, data := range tc.remote {
+			if strings.Contains(url, "/tile/") {
+				for i := range data {
+					data[i] ^= 0x80
+				}
+			}
+		}
+	}
+
+	// Bad tiles in initial download.
+	tc.mustHaveLatest(1)
+	flipBits()
+	_, err := tc.client.Lookup("rsc.io/sampler", "v1.3.0")
+	tc.mustError(err, "rsc.io/sampler@v1.3.0: initializing sumdb.Client: checking tree#1: downloaded inconsistent tile")
+	flipBits()
+	tc.newClient()
+	tc.mustLookup("rsc.io/sampler", "v1.3.0", "rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=")
+
+	// Bad tiles after initial download.
+	flipBits()
+	_, err = tc.client.Lookup("rsc.io/Quote", "v1.5.2")
+	tc.mustError(err, "rsc.io/Quote@v1.5.2: checking tree#3 against tree#4: downloaded inconsistent tile")
+	flipBits()
+	tc.newClient()
+	tc.mustLookup("rsc.io/Quote", "v1.5.2", "rsc.io/Quote v1.5.2 h1:uppercase!=")
+
+	// Bad starting tree hash looks like bad tiles.
+	tc.newClient()
+	text := tlog.FormatTree(tlog.Tree{N: 1, Hash: tlog.Hash{}})
+	data, err := note.Sign(&note.Note{Text: string(text)}, tc.signer)
+	if err != nil {
+		tc.t.Fatal(err)
+	}
+	tc.config[testName+"/latest"] = data
+	_, err = tc.client.Lookup("rsc.io/sampler", "v1.3.0")
+	tc.mustError(err, "rsc.io/sampler@v1.3.0: initializing sumdb.Client: checking tree#1: downloaded inconsistent tile")
+}
+
+func TestClientFork(t *testing.T) {
+	tc := newTestClient(t)
+	tc2 := tc.fork()
+
+	tc.addRecord("rsc.io/pkg1@v1.5.2", `rsc.io/pkg1 v1.5.2 h1:hash!=
+`)
+	tc.addRecord("rsc.io/pkg1@v1.5.4", `rsc.io/pkg1 v1.5.4 h1:hash!=
+`)
+	tc.mustLookup("rsc.io/pkg1", "v1.5.2", "rsc.io/pkg1 v1.5.2 h1:hash!=")
+
+	tc2.addRecord("rsc.io/pkg1@v1.5.3", `rsc.io/pkg1 v1.5.3 h1:hash!=
+`)
+	tc2.addRecord("rsc.io/pkg1@v1.5.4", `rsc.io/pkg1 v1.5.4 h1:hash!=
+`)
+	tc2.mustLookup("rsc.io/pkg1", "v1.5.4", "rsc.io/pkg1 v1.5.4 h1:hash!=")
+
+	key := "/lookup/rsc.io/pkg1@v1.5.2"
+	tc2.remote[key] = tc.remote[key]
+	_, err := tc2.client.Lookup("rsc.io/pkg1", "v1.5.2")
+	tc2.mustError(err, ErrSecurity.Error())
+
+	/*
+	   SECURITY ERROR
+	   go.sum database server misbehavior detected!
+
+	   old database:
+	   	go.sum database tree!
+	   	5
+	   	nWzN20+pwMt62p7jbv1/NlN95ePTlHijabv5zO/s36w=
+
+	   	— localhost.localdev/sumdb AAAMZ5/2FVAdMH58kmnz/0h299pwyskEbzDzoa2/YaPdhvLya4YWDFQQxu2TQb5GpwAH4NdWnTwuhILafisyf3CNbgg=
+
+	   new database:
+	   	go.sum database tree
+	   	6
+	   	wc4SkQt52o5W2nQ8To2ARs+mWuUJjss+sdleoiqxMmM=
+
+	   	— localhost.localdev/sumdb AAAMZ6oRNswlEZ6ZZhxrCvgl1MBy+nusq4JU+TG6Fe2NihWLqOzb+y2c2kzRLoCr4tvw9o36ucQEnhc20e4nA4Qc/wc=
+
+	   proof of misbehavior:
+	   	T7i+H/8ER4nXOiw4Bj0koZOkGjkxoNvlI34GpvhHhQg=
+	   	Nsuejv72de9hYNM5bqFv8rv3gm3zJQwv/DT/WNbLDLA=
+	   	mOmqqZ1aI/lzS94oq/JSbj7pD8Rv9S+xDyi12BtVSHo=
+	   	/7Aw5jVSMM9sFjQhaMg+iiDYPMk6decH7QLOGrL9Lx0=
+	*/
+
+	wants := []string{
+		"SECURITY ERROR",
+		"go.sum database server misbehavior detected!",
+		"old database:\n\tgo.sum database tree\n\t5\n",
+		"— localhost.localdev/sumdb AAAMZ5/2FVAd",
+		"new database:\n\tgo.sum database tree\n\t6\n",
+		"— localhost.localdev/sumdb AAAMZ6oRNswl",
+		"proof of misbehavior:\n\tT7i+H/8ER4nXOiw4Bj0k",
+	}
+	text := tc2.security.String()
+	for _, want := range wants {
+		if !strings.Contains(text, want) {
+			t.Fatalf("cannot find %q in security text:\n%s", want, text)
+		}
+	}
+}
+
+func TestClientGONOSUMDB(t *testing.T) {
+	tc := newTestClient(t)
+	tc.client.SetGONOSUMDB("p,*/q")
+	tc.client.Lookup("rsc.io/sampler", "v1.3.0") // initialize before we turn off network
+	tc.getOK = false
+
+	ok := []string{
+		"abc",
+		"a/p",
+		"pq",
+		"q",
+		"n/o/p/q",
+	}
+	skip := []string{
+		"p",
+		"p/x",
+		"x/q",
+		"x/q/z",
+	}
+
+	for _, path := range ok {
+		_, err := tc.client.Lookup(path, "v1.0.0")
+		if err == ErrGONOSUMDB {
+			t.Errorf("Lookup(%q): ErrGONOSUMDB, wanted failed actual lookup", path)
+		}
+	}
+	for _, path := range skip {
+		_, err := tc.client.Lookup(path, "v1.0.0")
+		if err != ErrGONOSUMDB {
+			t.Errorf("Lookup(%q): %v, wanted ErrGONOSUMDB", path, err)
+		}
+	}
+}
+
+// A testClient is a self-contained client-side testing environment.
+type testClient struct {
+	t          *testing.T // active test
+	client     *Client    // client being tested
+	tileHeight int        // tile height to use (default 2)
+	getOK      bool       // should tc.GetURL succeed?
+	getTileOK  bool       // should tc.GetURL of tiles succeed?
+	treeSize   int64
+	hashes     []tlog.Hash
+	remote     map[string][]byte
+	signer     note.Signer
+
+	// mu protects config, cache, log, security
+	// during concurrent use of the exported methods
+	// by the client itself (testClient is the Client's ClientOps,
+	// and the Client methods can both read and write these fields).
+	// Unexported methods invoked directly by the test
+	// (for example, addRecord) need not hold the mutex:
+	// for proper test execution those methods should only
+	// be called when the Client is idle and not using its ClientOps.
+	// Not holding the mutex in those methods ensures
+	// that if a mistake is made, go test -race will report it.
+	// (Holding the mutex would eliminate the race report but
+	// not the underlying problem.)
+	// Similarly, the get map is not protected by the mutex,
+	// because the Client methods only read it.
+	mu       sync.Mutex // prot
+	config   map[string][]byte
+	cache    map[string][]byte
+	security bytes.Buffer
+}
+
+// newTestClient returns a new testClient that will call t.Fatal on error
+// and has a few records already available on the remote server.
+func newTestClient(t *testing.T) *testClient {
+	tc := &testClient{
+		t:          t,
+		tileHeight: 2,
+		getOK:      true,
+		getTileOK:  true,
+		config:     make(map[string][]byte),
+		cache:      make(map[string][]byte),
+		remote:     make(map[string][]byte),
+	}
+
+	tc.config["key"] = []byte(testVerifierKey + "\n")
+	var err error
+	tc.signer, err = note.NewSigner(testSignerKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tc.newClient()
+
+	tc.addRecord("rsc.io/quote@v1.5.2", `rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
+rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
+rsc.io/quote v1.5.2 h2:xyzzy
+`)
+
+	tc.addRecord("golang.org/x/text@v0.0.0-20170915032832-14c0d48ead0c", `golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:qgOY6WgZOaTkIIMiVjBQcw93ERBE4m30iBm00nkL0i8=
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+`)
+	tc.addRecord("rsc.io/sampler@v1.3.0", `rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
+`)
+	tc.config[testName+"/latest"] = tc.signTree(1)
+
+	tc.addRecord("rsc.io/!quote@v1.5.2", `rsc.io/Quote v1.5.2 h1:uppercase!=
+`)
+	return tc
+}
+
+// newClient resets the Client associated with tc.
+// This clears any in-memory cache from the Client
+// but not tc's on-disk cache.
+func (tc *testClient) newClient() {
+	tc.client = NewClient(tc)
+	tc.client.SetTileHeight(tc.tileHeight)
+}
+
+// mustLookup does a lookup for path@vers and checks that the lines that come back match want.
+func (tc *testClient) mustLookup(path, vers, want string) {
+	tc.t.Helper()
+	lines, err := tc.client.Lookup(path, vers)
+	if err != nil {
+		tc.t.Fatal(err)
+	}
+	if strings.Join(lines, "\n") != want {
+		tc.t.Fatalf("Lookup(%q, %q):\n\t%s\nwant:\n\t%s", path, vers, strings.Join(lines, "\n\t"), strings.Replace(want, "\n", "\n\t", -1))
+	}
+}
+
+// mustHaveLatest checks that the on-disk configuration
+// for latest is a tree of size n.
+func (tc *testClient) mustHaveLatest(n int64) {
+	tc.t.Helper()
+
+	latest := tc.config[testName+"/latest"]
+	lines := strings.Split(string(latest), "\n")
+	if len(lines) < 2 || lines[1] != fmt.Sprint(n) {
+		tc.t.Fatalf("/latest should have tree %d, but has:\n%s", n, latest)
+	}
+}
+
+// mustError checks that err's error string contains the text.
+func (tc *testClient) mustError(err error, text string) {
+	tc.t.Helper()
+	if err == nil || !strings.Contains(err.Error(), text) {
+		tc.t.Fatalf("err = %v, want %q", err, text)
+	}
+}
+
+// fork returns a copy of tc.
+// Changes made to the new copy or to tc are not reflected in the other.
+func (tc *testClient) fork() *testClient {
+	tc2 := &testClient{
+		t:          tc.t,
+		getOK:      tc.getOK,
+		getTileOK:  tc.getTileOK,
+		tileHeight: tc.tileHeight,
+		treeSize:   tc.treeSize,
+		hashes:     append([]tlog.Hash{}, tc.hashes...),
+		signer:     tc.signer,
+		config:     copyMap(tc.config),
+		cache:      copyMap(tc.cache),
+		remote:     copyMap(tc.remote),
+	}
+	tc2.newClient()
+	return tc2
+}
+
+func copyMap(m map[string][]byte) map[string][]byte {
+	m2 := make(map[string][]byte)
+	for k, v := range m {
+		m2[k] = v
+	}
+	return m2
+}
+
+// ReadHashes is tc's implementation of tlog.HashReader, for use with
+// tlog.TreeHash and so on.
+func (tc *testClient) ReadHashes(indexes []int64) ([]tlog.Hash, error) {
+	var list []tlog.Hash
+	for _, id := range indexes {
+		list = append(list, tc.hashes[id])
+	}
+	return list, nil
+}
+
+// addRecord adds a log record using the given (!-encoded) key and data.
+func (tc *testClient) addRecord(key, data string) {
+	tc.t.Helper()
+
+	// Create record, add hashes to log tree.
+	id := tc.treeSize
+	tc.treeSize++
+	rec, err := tlog.FormatRecord(id, []byte(data))
+	if err != nil {
+		tc.t.Fatal(err)
+	}
+	hashes, err := tlog.StoredHashesForRecordHash(id, tlog.RecordHash([]byte(data)), tc)
+	if err != nil {
+		tc.t.Fatal(err)
+	}
+	tc.hashes = append(tc.hashes, hashes...)
+
+	// Create lookup result.
+	tc.remote["/lookup/"+key] = append(rec, tc.signTree(tc.treeSize)...)
+
+	// Create new tiles.
+	tiles := tlog.NewTiles(tc.tileHeight, id, tc.treeSize)
+	for _, tile := range tiles {
+		data, err := tlog.ReadTileData(tile, tc)
+		if err != nil {
+			tc.t.Fatal(err)
+		}
+		tc.remote["/"+tile.Path()] = data
+		// TODO delete old partial tiles
+	}
+}
+
+// signTree returns the signed head for the tree of the given size.
+func (tc *testClient) signTree(size int64) []byte {
+	h, err := tlog.TreeHash(size, tc)
+	if err != nil {
+		tc.t.Fatal(err)
+	}
+	text := tlog.FormatTree(tlog.Tree{N: size, Hash: h})
+	data, err := note.Sign(&note.Note{Text: string(text)}, tc.signer)
+	if err != nil {
+		tc.t.Fatal(err)
+	}
+	return data
+}
+
+// ReadRemote is for tc's implementation of Client.
+func (tc *testClient) ReadRemote(path string) ([]byte, error) {
+	// No mutex here because only the Client should be running
+	// and the Client cannot change tc.get.
+	if !tc.getOK {
+		return nil, fmt.Errorf("disallowed remote read %s", path)
+	}
+	if strings.Contains(path, "/tile/") && !tc.getTileOK {
+		return nil, fmt.Errorf("disallowed remote tile read %s", path)
+	}
+
+	data, ok := tc.remote[path]
+	if !ok {
+		return nil, fmt.Errorf("no remote path %s", path)
+	}
+	return data, nil
+}
+
+// ReadConfig is for tc's implementation of Client.
+func (tc *testClient) ReadConfig(file string) ([]byte, error) {
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+
+	data, ok := tc.config[file]
+	if !ok {
+		return nil, fmt.Errorf("no config %s", file)
+	}
+	return data, nil
+}
+
+// WriteConfig is for tc's implementation of Client.
+func (tc *testClient) WriteConfig(file string, old, new []byte) error {
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+
+	data := tc.config[file]
+	if !bytes.Equal(old, data) {
+		return ErrWriteConflict
+	}
+	tc.config[file] = new
+	return nil
+}
+
+// ReadCache is for tc's implementation of Client.
+func (tc *testClient) ReadCache(file string) ([]byte, error) {
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+
+	data, ok := tc.cache[file]
+	if !ok {
+		return nil, fmt.Errorf("no cache %s", file)
+	}
+	return data, nil
+}
+
+// WriteCache is for tc's implementation of Client.
+func (tc *testClient) WriteCache(file string, data []byte) {
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+
+	tc.cache[file] = data
+}
+
+// Log is for tc's implementation of Client.
+func (tc *testClient) Log(msg string) {
+	tc.t.Log(msg)
+}
+
+// SecurityError is for tc's implementation of Client.
+func (tc *testClient) SecurityError(msg string) {
+	tc.mu.Lock()
+	defer tc.mu.Unlock()
+
+	fmt.Fprintf(&tc.security, "%s\n", strings.TrimRight(msg, "\n"))
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/dirhash/hash.go

@@ -0,0 +1,135 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package dirhash defines hashes over directory trees.
+// These hashes are recorded in go.sum files and in the Go checksum database,
+// to allow verifying that a newly-downloaded module has the expected content.
+package dirhash
+
+import (
+	"archive/zip"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// DefaultHash is the default hash function used in new go.sum entries.
+var DefaultHash Hash = Hash1
+
+// A Hash is a directory hash function.
+// It accepts a list of files along with a function that opens the content of each file.
+// It opens, reads, hashes, and closes each file and returns the overall directory hash.
+type Hash func(files []string, open func(string) (io.ReadCloser, error)) (string, error)
+
+// Hash1 is the "h1:" directory hash function, using SHA-256.
+//
+// Hash1 is "h1:" followed by the base64-encoded SHA-256 hash of a summary
+// prepared as if by the Unix command:
+//
+//	sha256sum $(find . -type f | sort) | sha256sum
+//
+// More precisely, the hashed summary contains a single line for each file in the list,
+// ordered by sort.Strings applied to the file names, where each line consists of
+// the hexadecimal SHA-256 hash of the file content,
+// two spaces (U+0020), the file name, and a newline (U+000A).
+//
+// File names with newlines (U+000A) are disallowed.
+func Hash1(files []string, open func(string) (io.ReadCloser, error)) (string, error) {
+	h := sha256.New()
+	files = append([]string(nil), files...)
+	sort.Strings(files)
+	for _, file := range files {
+		if strings.Contains(file, "\n") {
+			return "", errors.New("dirhash: filenames with newlines are not supported")
+		}
+		r, err := open(file)
+		if err != nil {
+			return "", err
+		}
+		hf := sha256.New()
+		_, err = io.Copy(hf, r)
+		r.Close()
+		if err != nil {
+			return "", err
+		}
+		fmt.Fprintf(h, "%x  %s\n", hf.Sum(nil), file)
+	}
+	return "h1:" + base64.StdEncoding.EncodeToString(h.Sum(nil)), nil
+}
+
+// HashDir returns the hash of the local file system directory dir,
+// replacing the directory name itself with prefix in the file names
+// used in the hash function.
+func HashDir(dir, prefix string, hash Hash) (string, error) {
+	files, err := DirFiles(dir, prefix)
+	if err != nil {
+		return "", err
+	}
+	osOpen := func(name string) (io.ReadCloser, error) {
+		return os.Open(filepath.Join(dir, strings.TrimPrefix(name, prefix)))
+	}
+	return hash(files, osOpen)
+}
+
+// DirFiles returns the list of files in the tree rooted at dir,
+// replacing the directory name dir with prefix in each name.
+// The resulting names always use forward slashes.
+func DirFiles(dir, prefix string) ([]string, error) {
+	var files []string
+	dir = filepath.Clean(dir)
+	err := filepath.Walk(dir, func(file string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		} else if file == dir {
+			return fmt.Errorf("%s is not a directory", dir)
+		}
+
+		rel := file
+		if dir != "." {
+			rel = file[len(dir)+1:]
+		}
+		f := filepath.Join(prefix, rel)
+		files = append(files, filepath.ToSlash(f))
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return files, nil
+}
+
+// HashZip returns the hash of the file content in the named zip file.
+// Only the file names and their contents are included in the hash:
+// the exact zip file format encoding, compression method,
+// per-file modification times, and other metadata are ignored.
+func HashZip(zipfile string, hash Hash) (string, error) {
+	z, err := zip.OpenReader(zipfile)
+	if err != nil {
+		return "", err
+	}
+	defer z.Close()
+	var files []string
+	zfiles := make(map[string]*zip.File)
+	for _, file := range z.File {
+		files = append(files, file.Name)
+		zfiles[file.Name] = file
+	}
+	zipOpen := func(name string) (io.ReadCloser, error) {
+		f := zfiles[name]
+		if f == nil {
+			return nil, fmt.Errorf("file %q not found in zip", name) // should never happen
+		}
+		return f.Open()
+	}
+	return hash(files, zipOpen)
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/dirhash/hash_test.go

@@ -0,0 +1,143 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package dirhash
+
+import (
+	"archive/zip"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func h(s string) string {
+	return fmt.Sprintf("%x", sha256.Sum256([]byte(s)))
+}
+
+func htop(k string, s string) string {
+	sum := sha256.Sum256([]byte(s))
+	return k + ":" + base64.StdEncoding.EncodeToString(sum[:])
+}
+
+func TestHash1(t *testing.T) {
+	files := []string{"xyz", "abc"}
+	open := func(name string) (io.ReadCloser, error) {
+		return io.NopCloser(strings.NewReader("data for " + name)), nil
+	}
+	want := htop("h1", fmt.Sprintf("%s  %s\n%s  %s\n", h("data for abc"), "abc", h("data for xyz"), "xyz"))
+	out, err := Hash1(files, open)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out != want {
+		t.Errorf("Hash1(...) = %s, want %s", out, want)
+	}
+
+	_, err = Hash1([]string{"xyz", "a\nbc"}, open)
+	if err == nil {
+		t.Error("Hash1: expected error on newline in filenames")
+	}
+}
+
+func TestHashDir(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, "xyz"), []byte("data for xyz"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "abc"), []byte("data for abc"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	want := htop("h1", fmt.Sprintf("%s  %s\n%s  %s\n", h("data for abc"), "prefix/abc", h("data for xyz"), "prefix/xyz"))
+	out, err := HashDir(dir, "prefix", Hash1)
+	if err != nil {
+		t.Fatalf("HashDir: %v", err)
+	}
+	if out != want {
+		t.Errorf("HashDir(...) = %s, want %s", out, want)
+	}
+}
+
+func TestHashZip(t *testing.T) {
+	f, err := os.CreateTemp(t.TempDir(), "dirhash-test-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	z := zip.NewWriter(f)
+	w, err := z.Create("prefix/xyz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	w.Write([]byte("data for xyz"))
+	w, err = z.Create("prefix/abc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	w.Write([]byte("data for abc"))
+	if err := z.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	want := htop("h1", fmt.Sprintf("%s  %s\n%s  %s\n", h("data for abc"), "prefix/abc", h("data for xyz"), "prefix/xyz"))
+	out, err := HashZip(f.Name(), Hash1)
+	if err != nil {
+		t.Fatalf("HashDir: %v", err)
+	}
+	if out != want {
+		t.Errorf("HashDir(...) = %s, want %s", out, want)
+	}
+}
+
+func TestDirFiles(t *testing.T) {
+	t.Run("valid directory with files", func(t *testing.T) {
+		dir := t.TempDir()
+		if err := os.WriteFile(filepath.Join(dir, "xyz"), []byte("data for xyz"), 0666); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(dir, "abc"), []byte("data for abc"), 0666); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.Mkdir(filepath.Join(dir, "subdir"), 0777); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(dir, "subdir", "xyz"), []byte("data for subdir xyz"), 0666); err != nil {
+			t.Fatal(err)
+		}
+		prefix := "foo/bar@v2.3.4"
+		out, err := DirFiles(dir, prefix)
+		if err != nil {
+			t.Fatalf("DirFiles: %v", err)
+		}
+		for _, file := range out {
+			if !strings.HasPrefix(file, prefix) {
+				t.Errorf("Dir file = %s, want prefix %s", file, prefix)
+			}
+		}
+	})
+
+	t.Run("invalid directory", func(t *testing.T) {
+		path := filepath.Join(t.TempDir(), "not-a-directory.txt")
+		if err := os.WriteFile(path, []byte("This is a file."), 0644); err != nil {
+			t.Fatal(err)
+		}
+		defer os.RemoveAll(path)
+
+		out, err := DirFiles(path, "")
+		if err == nil {
+			t.Errorf("DirFiles(...) = %v, expected an error", err)
+		}
+		if len(out) > 0 {
+			t.Errorf("DirFiles(...) = unexpected files %s", out)
+		}
+	})
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/note/example_test.go

@@ -0,0 +1,128 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package note_test
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"golang.org/x/mod/sumdb/note"
+)
+
+func ExampleSign() {
+	skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+	text := "If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n"
+
+	signer, err := note.NewSigner(skey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	msg, err := note.Sign(&note.Note{Text: text}, signer)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	os.Stdout.Write(msg)
+
+	// Output:
+	// If you think cryptography is the answer to your problem,
+	// then you don't know what your problem is.
+	//
+	// — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+}
+
+func ExampleOpen() {
+	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	msg := []byte("If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n" +
+		"\n" +
+		"— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+	verifier, err := note.NewVerifier(vkey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	verifiers := note.VerifierList(verifier)
+
+	n, err := note.Open(msg, verifiers)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Printf("%s (%08x):\n%s", n.Sigs[0].Name, n.Sigs[0].Hash, n.Text)
+
+	// Output:
+	// PeterNeumann (c74f20a3):
+	// If you think cryptography is the answer to your problem,
+	// then you don't know what your problem is.
+}
+
+var rand = struct {
+	Reader io.Reader
+}{
+	zeroReader{},
+}
+
+type zeroReader struct{}
+
+func (zeroReader) Read(buf []byte) (int, error) {
+	for i := range buf {
+		buf[i] = 0
+	}
+	return len(buf), nil
+}
+
+func ExampleSign_add_signatures() {
+	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	msg := []byte("If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n" +
+		"\n" +
+		"— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+	verifier, err := note.NewVerifier(vkey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	verifiers := note.VerifierList(verifier)
+
+	n, err := note.Open(msg, verifiers)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	skey, vkey, err := note.GenerateKey(rand.Reader, "EnochRoot")
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	_ = vkey // give to verifiers
+
+	me, err := note.NewSigner(skey)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	msg, err = note.Sign(n, me)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	os.Stdout.Write(msg)
+
+	// Output:
+	// If you think cryptography is the answer to your problem,
+	// then you don't know what your problem is.
+	//
+	// — PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+	// — EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/note/note.go

@@ -0,0 +1,678 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package note defines the notes signed by the Go module database server.
+//
+// A note is text signed by one or more server keys.
+// The text should be ignored unless the note is signed by
+// a trusted server key and the signature has been verified
+// using the server's public key.
+//
+// A server's public key is identified by a name, typically the "host[/path]"
+// giving the base URL of the server's transparency log.
+// The syntactic restrictions on a name are that it be non-empty,
+// well-formed UTF-8 containing neither Unicode spaces nor plus (U+002B).
+//
+// A Go module database server signs texts using public key cryptography.
+// A given server may have multiple public keys, each
+// identified by a 32-bit hash of the public key.
+//
+// # Verifying Notes
+//
+// A [Verifier] allows verification of signatures by one server public key.
+// It can report the name of the server and the uint32 hash of the key,
+// and it can verify a purported signature by that key.
+//
+// The standard implementation of a Verifier is constructed
+// by [NewVerifier] starting from a verifier key, which is a
+// plain text string of the form "<name>+<hash>+<keydata>".
+//
+// A [Verifiers] allows looking up a Verifier by the combination
+// of server name and key hash.
+//
+// The standard implementation of a Verifiers is constructed
+// by VerifierList from a list of known verifiers.
+//
+// A [Note] represents a text with one or more signatures.
+// An implementation can reject a note with too many signatures
+// (for example, more than 100 signatures).
+//
+// A [Signature] represents a signature on a note, verified or not.
+//
+// The [Open] function takes as input a signed message
+// and a set of known verifiers. It decodes and verifies
+// the message signatures and returns a [Note] structure
+// containing the message text and (verified or unverified) signatures.
+//
+// # Signing Notes
+//
+// A [Signer] allows signing a text with a given key.
+// It can report the name of the server and the hash of the key
+// and can sign a raw text using that key.
+//
+// The standard implementation of a Signer is constructed
+// by [NewSigner] starting from an encoded signer key, which is a
+// plain text string of the form "PRIVATE+KEY+<name>+<hash>+<keydata>".
+// Anyone with an encoded signer key can sign messages using that key,
+// so it must be kept secret. The encoding begins with the literal text
+// "PRIVATE+KEY" to avoid confusion with the public server key.
+//
+// The [Sign] function takes as input a Note and a list of Signers
+// and returns an encoded, signed message.
+//
+// # Signed Note Format
+//
+// A signed note consists of a text ending in newline (U+000A),
+// followed by a blank line (only a newline),
+// followed by one or more signature lines of this form:
+// em dash (U+2014), space (U+0020),
+// server name, space, base64-encoded signature, newline.
+//
+// Signed notes must be valid UTF-8 and must not contain any
+// ASCII control characters (those below U+0020) other than newline.
+//
+// A signature is a base64 encoding of 4+n bytes.
+//
+// The first four bytes in the signature are the uint32 key hash
+// stored in big-endian order.
+//
+// The remaining n bytes are the result of using the specified key
+// to sign the note text (including the final newline but not the
+// separating blank line).
+//
+// # Generating Keys
+//
+// There is only one key type, Ed25519 with algorithm identifier 1.
+// New key types may be introduced in the future as needed,
+// although doing so will require deploying the new algorithms to all clients
+// before starting to depend on them for signatures.
+//
+// The [GenerateKey] function generates and returns a new signer
+// and corresponding verifier.
+//
+// # Example
+//
+// Here is a well-formed signed note:
+//
+//	If you think cryptography is the answer to your problem,
+//	then you don't know what your problem is.
+//
+//	— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+//
+// It can be constructed and displayed using:
+//
+//	skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+//	text := "If you think cryptography is the answer to your problem,\n" +
+//		"then you don't know what your problem is.\n"
+//
+//	signer, err := note.NewSigner(skey)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//
+//	msg, err := note.Sign(&note.Note{Text: text}, signer)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	os.Stdout.Write(msg)
+//
+// The note's text is two lines, including the final newline,
+// and the text is purportedly signed by a server named
+// "PeterNeumann". (Although server names are canonically
+// base URLs, the only syntactic requirement is that they
+// not contain spaces or newlines).
+//
+// If [Open] is given access to a [Verifiers] including the
+// [Verifier] for this key, then it will succeed at verifying
+// the encoded message and returning the parsed [Note]:
+//
+//	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+//	msg := []byte("If you think cryptography is the answer to your problem,\n" +
+//		"then you don't know what your problem is.\n" +
+//		"\n" +
+//		"— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+//
+//	verifier, err := note.NewVerifier(vkey)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	verifiers := note.VerifierList(verifier)
+//
+//	n, err := note.Open([]byte(msg), verifiers)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	fmt.Printf("%s (%08x):\n%s", n.Sigs[0].Name, n.Sigs[0].Hash, n.Text)
+//
+// You can add your own signature to this message by re-signing the note:
+//
+//	skey, vkey, err := note.GenerateKey(rand.Reader, "EnochRoot")
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	_ = vkey // give to verifiers
+//
+//	me, err := note.NewSigner(skey)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//
+//	msg, err := note.Sign(n, me)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	os.Stdout.Write(msg)
+//
+// This will print a doubly-signed message, like:
+//
+//	If you think cryptography is the answer to your problem,
+//	then you don't know what your problem is.
+//
+//	— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+//	— EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=
+package note
+
+import (
+	"bytes"
+	"crypto/ed25519"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A Verifier verifies messages signed with a specific key.
+type Verifier interface {
+	// Name returns the server name associated with the key.
+	Name() string
+
+	// KeyHash returns the key hash.
+	KeyHash() uint32
+
+	// Verify reports whether sig is a valid signature of msg.
+	Verify(msg, sig []byte) bool
+}
+
+// A Signer signs messages using a specific key.
+type Signer interface {
+	// Name returns the server name associated with the key.
+	Name() string
+
+	// KeyHash returns the key hash.
+	KeyHash() uint32
+
+	// Sign returns a signature for the given message.
+	Sign(msg []byte) ([]byte, error)
+}
+
+// keyHash computes the key hash for the given server name and encoded public key.
+func keyHash(name string, key []byte) uint32 {
+	h := sha256.New()
+	h.Write([]byte(name))
+	h.Write([]byte("\n"))
+	h.Write(key)
+	sum := h.Sum(nil)
+	return binary.BigEndian.Uint32(sum)
+}
+
+var (
+	errVerifierID   = errors.New("malformed verifier id")
+	errVerifierAlg  = errors.New("unknown verifier algorithm")
+	errVerifierHash = errors.New("invalid verifier hash")
+)
+
+const (
+	algEd25519 = 1
+)
+
+// isValidName reports whether name is valid.
+// It must be non-empty and not have any Unicode spaces or pluses.
+func isValidName(name string) bool {
+	return name != "" && utf8.ValidString(name) && strings.IndexFunc(name, unicode.IsSpace) < 0 && !strings.Contains(name, "+")
+}
+
+// NewVerifier construct a new [Verifier] from an encoded verifier key.
+func NewVerifier(vkey string) (Verifier, error) {
+	name, vkey := chop(vkey, "+")
+	hash16, key64 := chop(vkey, "+")
+	hash, err1 := strconv.ParseUint(hash16, 16, 32)
+	key, err2 := base64.StdEncoding.DecodeString(key64)
+	if len(hash16) != 8 || err1 != nil || err2 != nil || !isValidName(name) || len(key) == 0 {
+		return nil, errVerifierID
+	}
+	if uint32(hash) != keyHash(name, key) {
+		return nil, errVerifierHash
+	}
+
+	v := &verifier{
+		name: name,
+		hash: uint32(hash),
+	}
+
+	alg, key := key[0], key[1:]
+	switch alg {
+	default:
+		return nil, errVerifierAlg
+
+	case algEd25519:
+		if len(key) != 32 {
+			return nil, errVerifierID
+		}
+		v.verify = func(msg, sig []byte) bool {
+			return ed25519.Verify(key, msg, sig)
+		}
+	}
+
+	return v, nil
+}
+
+// chop chops s at the first instance of sep, if any,
+// and returns the text before and after sep.
+// If sep is not present, chop returns before is s and after is empty.
+func chop(s, sep string) (before, after string) {
+	i := strings.Index(s, sep)
+	if i < 0 {
+		return s, ""
+	}
+	return s[:i], s[i+len(sep):]
+}
+
+// verifier is a trivial Verifier implementation.
+type verifier struct {
+	name   string
+	hash   uint32
+	verify func([]byte, []byte) bool
+}
+
+func (v *verifier) Name() string                { return v.name }
+func (v *verifier) KeyHash() uint32             { return v.hash }
+func (v *verifier) Verify(msg, sig []byte) bool { return v.verify(msg, sig) }
+
+// NewSigner constructs a new [Signer] from an encoded signer key.
+func NewSigner(skey string) (Signer, error) {
+	priv1, skey := chop(skey, "+")
+	priv2, skey := chop(skey, "+")
+	name, skey := chop(skey, "+")
+	hash16, key64 := chop(skey, "+")
+	hash, err1 := strconv.ParseUint(hash16, 16, 32)
+	key, err2 := base64.StdEncoding.DecodeString(key64)
+	if priv1 != "PRIVATE" || priv2 != "KEY" || len(hash16) != 8 || err1 != nil || err2 != nil || !isValidName(name) || len(key) == 0 {
+		return nil, errSignerID
+	}
+
+	// Note: hash is the hash of the public key and we have the private key.
+	// Must verify hash after deriving public key.
+
+	s := &signer{
+		name: name,
+		hash: uint32(hash),
+	}
+
+	var pubkey []byte
+
+	alg, key := key[0], key[1:]
+	switch alg {
+	default:
+		return nil, errSignerAlg
+
+	case algEd25519:
+		if len(key) != 32 {
+			return nil, errSignerID
+		}
+		key = ed25519.NewKeyFromSeed(key)
+		pubkey = append([]byte{algEd25519}, key[32:]...)
+		s.sign = func(msg []byte) ([]byte, error) {
+			return ed25519.Sign(key, msg), nil
+		}
+	}
+
+	if uint32(hash) != keyHash(name, pubkey) {
+		return nil, errSignerHash
+	}
+
+	return s, nil
+}
+
+var (
+	errSignerID   = errors.New("malformed verifier id")
+	errSignerAlg  = errors.New("unknown verifier algorithm")
+	errSignerHash = errors.New("invalid verifier hash")
+)
+
+// signer is a trivial Signer implementation.
+type signer struct {
+	name string
+	hash uint32
+	sign func([]byte) ([]byte, error)
+}
+
+func (s *signer) Name() string                    { return s.name }
+func (s *signer) KeyHash() uint32                 { return s.hash }
+func (s *signer) Sign(msg []byte) ([]byte, error) { return s.sign(msg) }
+
+// GenerateKey generates a signer and verifier key pair for a named server.
+// The signer key skey is private and must be kept secret.
+func GenerateKey(rand io.Reader, name string) (skey, vkey string, err error) {
+	pub, priv, err := ed25519.GenerateKey(rand)
+	if err != nil {
+		return "", "", err
+	}
+	pubkey := append([]byte{algEd25519}, pub...)
+	privkey := append([]byte{algEd25519}, priv.Seed()...)
+	h := keyHash(name, pubkey)
+
+	skey = fmt.Sprintf("PRIVATE+KEY+%s+%08x+%s", name, h, base64.StdEncoding.EncodeToString(privkey))
+	vkey = fmt.Sprintf("%s+%08x+%s", name, h, base64.StdEncoding.EncodeToString(pubkey))
+	return skey, vkey, nil
+}
+
+// NewEd25519VerifierKey returns an encoded verifier key using the given name
+// and Ed25519 public key.
+func NewEd25519VerifierKey(name string, key ed25519.PublicKey) (string, error) {
+	if len(key) != ed25519.PublicKeySize {
+		return "", fmt.Errorf("invalid public key size %d, expected %d", len(key), ed25519.PublicKeySize)
+	}
+
+	pubkey := append([]byte{algEd25519}, key...)
+	hash := keyHash(name, pubkey)
+
+	b64Key := base64.StdEncoding.EncodeToString(pubkey)
+	return fmt.Sprintf("%s+%08x+%s", name, hash, b64Key), nil
+}
+
+// A Verifiers is a collection of known verifier keys.
+type Verifiers interface {
+	// Verifier returns the Verifier associated with the key
+	// identified by the name and hash.
+	// If the name, hash pair is unknown, Verifier should return
+	// an UnknownVerifierError.
+	Verifier(name string, hash uint32) (Verifier, error)
+}
+
+// An UnknownVerifierError indicates that the given key is not known.
+// The Open function records signatures without associated verifiers as
+// unverified signatures.
+type UnknownVerifierError struct {
+	Name    string
+	KeyHash uint32
+}
+
+func (e *UnknownVerifierError) Error() string {
+	return fmt.Sprintf("unknown key %s+%08x", e.Name, e.KeyHash)
+}
+
+// An ambiguousVerifierError indicates that the given name and hash
+// match multiple keys passed to [VerifierList].
+// (If this happens, some malicious actor has taken control of the
+// verifier list, at which point we may as well give up entirely,
+// but we diagnose the problem instead.)
+type ambiguousVerifierError struct {
+	name string
+	hash uint32
+}
+
+func (e *ambiguousVerifierError) Error() string {
+	return fmt.Sprintf("ambiguous key %s+%08x", e.name, e.hash)
+}
+
+// VerifierList returns a [Verifiers] implementation that uses the given list of verifiers.
+func VerifierList(list ...Verifier) Verifiers {
+	m := make(verifierMap)
+	for _, v := range list {
+		k := nameHash{v.Name(), v.KeyHash()}
+		m[k] = append(m[k], v)
+	}
+	return m
+}
+
+type nameHash struct {
+	name string
+	hash uint32
+}
+
+type verifierMap map[nameHash][]Verifier
+
+func (m verifierMap) Verifier(name string, hash uint32) (Verifier, error) {
+	v, ok := m[nameHash{name, hash}]
+	if !ok {
+		return nil, &UnknownVerifierError{name, hash}
+	}
+	if len(v) > 1 {
+		return nil, &ambiguousVerifierError{name, hash}
+	}
+	return v[0], nil
+}
+
+// A Note is a text and signatures.
+type Note struct {
+	Text           string      // text of note
+	Sigs           []Signature // verified signatures
+	UnverifiedSigs []Signature // unverified signatures
+}
+
+// A Signature is a single signature found in a note.
+type Signature struct {
+	// Name and Hash give the name and key hash
+	// for the key that generated the signature.
+	Name string
+	Hash uint32
+
+	// Base64 records the base64-encoded signature bytes.
+	Base64 string
+}
+
+// An UnverifiedNoteError indicates that the note
+// successfully parsed but had no verifiable signatures.
+type UnverifiedNoteError struct {
+	Note *Note
+}
+
+func (e *UnverifiedNoteError) Error() string {
+	return "note has no verifiable signatures"
+}
+
+// An InvalidSignatureError indicates that the given key was known
+// and the associated Verifier rejected the signature.
+type InvalidSignatureError struct {
+	Name string
+	Hash uint32
+}
+
+func (e *InvalidSignatureError) Error() string {
+	return fmt.Sprintf("invalid signature for key %s+%08x", e.Name, e.Hash)
+}
+
+var (
+	errMalformedNote      = errors.New("malformed note")
+	errInvalidSigner      = errors.New("invalid signer")
+	errMismatchedVerifier = errors.New("verifier name or hash doesn't match signature")
+
+	sigSplit  = []byte("\n\n")
+	sigPrefix = []byte("— ")
+)
+
+// Open opens and parses the message msg, checking signatures from the known verifiers.
+//
+// For each signature in the message, Open calls known.Verifier to find a verifier.
+// If known.Verifier returns a verifier and the verifier accepts the signature,
+// Open records the signature in the returned note's Sigs field.
+// If known.Verifier returns a verifier but the verifier rejects the signature,
+// Open returns an InvalidSignatureError.
+// If known.Verifier returns an UnknownVerifierError,
+// Open records the signature in the returned note's UnverifiedSigs field.
+// If known.Verifier returns any other error, Open returns that error.
+//
+// If no known verifier has signed an otherwise valid note,
+// Open returns an [UnverifiedNoteError].
+// In this case, the unverified note can be fetched from inside the error.
+func Open(msg []byte, known Verifiers) (*Note, error) {
+	if known == nil {
+		// Treat nil Verifiers as empty list, to produce useful error instead of crash.
+		known = VerifierList()
+	}
+
+	// Must have valid UTF-8 with no non-newline ASCII control characters.
+	for i := 0; i < len(msg); {
+		r, size := utf8.DecodeRune(msg[i:])
+		if r < 0x20 && r != '\n' || r == utf8.RuneError && size == 1 {
+			return nil, errMalformedNote
+		}
+		i += size
+	}
+
+	// Must end with signature block preceded by blank line.
+	split := bytes.LastIndex(msg, sigSplit)
+	if split < 0 {
+		return nil, errMalformedNote
+	}
+	text, sigs := msg[:split+1], msg[split+2:]
+	if len(sigs) == 0 || sigs[len(sigs)-1] != '\n' {
+		return nil, errMalformedNote
+	}
+
+	n := &Note{
+		Text: string(text),
+	}
+
+	// Parse and verify signatures.
+	// Ignore duplicate signatures.
+	seen := make(map[nameHash]bool)
+	seenUnverified := make(map[string]bool)
+	numSig := 0
+	for len(sigs) > 0 {
+		// Pull out next signature line.
+		// We know sigs[len(sigs)-1] == '\n', so IndexByte always finds one.
+		i := bytes.IndexByte(sigs, '\n')
+		line := sigs[:i]
+		sigs = sigs[i+1:]
+
+		if !bytes.HasPrefix(line, sigPrefix) {
+			return nil, errMalformedNote
+		}
+		line = line[len(sigPrefix):]
+		name, b64 := chop(string(line), " ")
+		sig, err := base64.StdEncoding.DecodeString(b64)
+		if err != nil || !isValidName(name) || b64 == "" || len(sig) < 5 {
+			return nil, errMalformedNote
+		}
+		hash := binary.BigEndian.Uint32(sig[0:4])
+		sig = sig[4:]
+
+		if numSig++; numSig > 100 {
+			// Avoid spending forever parsing a note with many signatures.
+			return nil, errMalformedNote
+		}
+
+		v, err := known.Verifier(name, hash)
+		if _, ok := err.(*UnknownVerifierError); ok {
+			// Drop repeated identical unverified signatures.
+			if seenUnverified[string(line)] {
+				continue
+			}
+			seenUnverified[string(line)] = true
+			n.UnverifiedSigs = append(n.UnverifiedSigs, Signature{Name: name, Hash: hash, Base64: b64})
+			continue
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		// Check that known.Verifier returned the right verifier.
+		if v.Name() != name || v.KeyHash() != hash {
+			return nil, errMismatchedVerifier
+		}
+
+		// Drop repeated signatures by a single verifier.
+		if seen[nameHash{name, hash}] {
+			continue
+		}
+		seen[nameHash{name, hash}] = true
+
+		ok := v.Verify(text, sig)
+		if !ok {
+			return nil, &InvalidSignatureError{name, hash}
+		}
+
+		n.Sigs = append(n.Sigs, Signature{Name: name, Hash: hash, Base64: b64})
+	}
+
+	// Parsed and verified all the signatures.
+	if len(n.Sigs) == 0 {
+		return nil, &UnverifiedNoteError{n}
+	}
+	return n, nil
+}
+
+// Sign signs the note with the given signers and returns the encoded message.
+// The new signatures from signers are listed in the encoded message after
+// the existing signatures already present in n.Sigs.
+// If any signer uses the same key as an existing signature,
+// the existing signature is elided from the output.
+func Sign(n *Note, signers ...Signer) ([]byte, error) {
+	var buf bytes.Buffer
+	if !strings.HasSuffix(n.Text, "\n") {
+		return nil, errMalformedNote
+	}
+	buf.WriteString(n.Text)
+
+	// Prepare signatures.
+	var sigs bytes.Buffer
+	have := make(map[nameHash]bool)
+	for _, s := range signers {
+		name := s.Name()
+		hash := s.KeyHash()
+		have[nameHash{name, hash}] = true
+		if !isValidName(name) {
+			return nil, errInvalidSigner
+		}
+
+		sig, err := s.Sign(buf.Bytes()) // buf holds n.Text
+		if err != nil {
+			return nil, err
+		}
+
+		var hbuf [4]byte
+		binary.BigEndian.PutUint32(hbuf[:], hash)
+		b64 := base64.StdEncoding.EncodeToString(append(hbuf[:], sig...))
+		sigs.WriteString("— ")
+		sigs.WriteString(name)
+		sigs.WriteString(" ")
+		sigs.WriteString(b64)
+		sigs.WriteString("\n")
+	}
+
+	buf.WriteString("\n")
+
+	// Emit existing signatures not replaced by new ones.
+	for _, list := range [][]Signature{n.Sigs, n.UnverifiedSigs} {
+		for _, sig := range list {
+			name, hash := sig.Name, sig.Hash
+			if !isValidName(name) {
+				return nil, errMalformedNote
+			}
+			if have[nameHash{name, hash}] {
+				continue
+			}
+			// Double-check hash against base64.
+			raw, err := base64.StdEncoding.DecodeString(sig.Base64)
+			if err != nil || len(raw) < 4 || binary.BigEndian.Uint32(raw) != hash {
+				return nil, errMalformedNote
+			}
+			buf.WriteString("— ")
+			buf.WriteString(sig.Name)
+			buf.WriteString(" ")
+			buf.WriteString(sig.Base64)
+			buf.WriteString("\n")
+		}
+	}
+	buf.Write(sigs.Bytes())
+
+	return buf.Bytes(), nil
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/note/note_test.go

@@ -0,0 +1,490 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package note
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"errors"
+	"strings"
+	"testing"
+	"testing/iotest"
+)
+
+func TestNewVerifier(t *testing.T) {
+	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	_, err := NewVerifier(vkey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Check various manglings are not accepted.
+	badKey := func(k string) {
+		_, err := NewVerifier(k)
+		if err == nil {
+			t.Errorf("NewVerifier(%q) succeeded, should have failed", k)
+		}
+	}
+
+	b := []byte(vkey)
+	for i := 0; i <= len(b); i++ {
+		for j := i + 1; j <= len(b); j++ {
+			if i != 0 || j != len(b) {
+				badKey(string(b[i:j]))
+			}
+		}
+	}
+	for i := 0; i < len(b); i++ {
+		b[i]++
+		badKey(string(b))
+		b[i]--
+	}
+
+	badKey("PeterNeumann+cc469956+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TWBADKEY==") // wrong length key, with adjusted key hash
+	badKey("PeterNeumann+173116ae+ZRpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW")         // unknown algorithm, with adjusted key hash
+}
+
+func TestNewSigner(t *testing.T) {
+	skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+	_, err := NewSigner(skey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Check various manglings are not accepted.
+	b := []byte(skey)
+	for i := 0; i <= len(b); i++ {
+		for j := i + 1; j <= len(b); j++ {
+			if i == 0 && j == len(b) {
+				continue
+			}
+			_, err := NewSigner(string(b[i:j]))
+			if err == nil {
+				t.Errorf("NewSigner(%q) succeeded, should have failed", b[i:j])
+			}
+		}
+	}
+	for i := 0; i < len(b); i++ {
+		b[i]++
+		_, err := NewSigner(string(b))
+		if err == nil {
+			t.Errorf("NewSigner(%q) succeeded, should have failed", b)
+		}
+		b[i]--
+	}
+}
+
+func testSignerAndVerifier(t *testing.T, Name string, signer Signer, verifier Verifier) {
+	if name := signer.Name(); name != Name {
+		t.Errorf("signer.Name() = %q, want %q", name, Name)
+	}
+	if name := verifier.Name(); name != Name {
+		t.Errorf("verifier.Name() = %q, want %q", name, Name)
+	}
+	shash := signer.KeyHash()
+	vhash := verifier.KeyHash()
+	if shash != vhash {
+		t.Errorf("signer.KeyHash() = %#08x != verifier.KeyHash() = %#08x", shash, vhash)
+	}
+
+	msg := []byte("hi")
+	sig, err := signer.Sign(msg)
+	if err != nil {
+		t.Fatalf("signer.Sign: %v", err)
+	}
+	if !verifier.Verify(msg, sig) {
+		t.Fatalf("verifier.Verify failed on signature returned by signer.Sign")
+	}
+	sig[0]++
+	if verifier.Verify(msg, sig) {
+		t.Fatalf("verifier.Verify succeeded on corrupt signature")
+	}
+	sig[0]--
+	msg[0]++
+	if verifier.Verify(msg, sig) {
+		t.Fatalf("verifier.Verify succeeded on corrupt message")
+	}
+}
+
+func TestGenerateKey(t *testing.T) {
+	// Generate key pair, make sure it is all self-consistent.
+	const Name = "EnochRoot"
+
+	skey, vkey, err := GenerateKey(rand.Reader, Name)
+	if err != nil {
+		t.Fatalf("GenerateKey: %v", err)
+	}
+	signer, err := NewSigner(skey)
+	if err != nil {
+		t.Fatalf("NewSigner: %v", err)
+	}
+	verifier, err := NewVerifier(vkey)
+	if err != nil {
+		t.Fatalf("NewVerifier: %v", err)
+	}
+
+	testSignerAndVerifier(t, Name, signer, verifier)
+
+	// Check that GenerateKey returns error from rand reader.
+	_, _, err = GenerateKey(iotest.TimeoutReader(iotest.OneByteReader(rand.Reader)), Name)
+	if err == nil {
+		t.Fatalf("GenerateKey succeeded with error-returning rand reader")
+	}
+}
+
+func TestFromEd25519(t *testing.T) {
+	const Name = "EnochRoot"
+
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatalf("GenerateKey: %v", err)
+	}
+	signer, err := newSignerFromEd25519Seed(Name, priv.Seed())
+	if err != nil {
+		t.Fatalf("newSignerFromEd25519Seed: %v", err)
+	}
+	vkey, err := NewEd25519VerifierKey(Name, pub)
+	if err != nil {
+		t.Fatalf("NewEd25519VerifierKey: %v", err)
+	}
+	verifier, err := NewVerifier(vkey)
+	if err != nil {
+		t.Fatalf("NewVerifier: %v", err)
+	}
+
+	testSignerAndVerifier(t, Name, signer, verifier)
+
+	// Check that wrong key sizes return errors.
+	_, err = NewEd25519VerifierKey(Name, pub[:len(pub)-1])
+	if err == nil {
+		t.Errorf("NewEd25519VerifierKey succeeded with a seed of the wrong size")
+	}
+}
+
+// newSignerFromEd25519Seed constructs a new signer from a verifier name and a
+// crypto/ed25519 private key seed.
+func newSignerFromEd25519Seed(name string, seed []byte) (Signer, error) {
+	if len(seed) != ed25519.SeedSize {
+		return nil, errors.New("invalid seed size")
+	}
+	priv := ed25519.NewKeyFromSeed(seed)
+	pub := priv[32:]
+
+	pubkey := append([]byte{algEd25519}, pub...)
+	hash := keyHash(name, pubkey)
+
+	s := &signer{
+		name: name,
+		hash: hash,
+		sign: func(msg []byte) ([]byte, error) {
+			return ed25519.Sign(priv, msg), nil
+		},
+	}
+	return s, nil
+}
+
+func TestSign(t *testing.T) {
+	skey := "PRIVATE+KEY+PeterNeumann+c74f20a3+AYEKFALVFGyNhPJEMzD1QIDr+Y7hfZx09iUvxdXHKDFz"
+	text := "If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n"
+
+	signer, err := NewSigner(skey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	msg, err := Sign(&Note{Text: text}, signer)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := `If you think cryptography is the answer to your problem,
+then you don't know what your problem is.
+
+— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=
+`
+	if string(msg) != want {
+		t.Errorf("Sign: wrong output\nhave:\n%s\nwant:\n%s", msg, want)
+	}
+
+	// Check that existing signature is replaced by new one.
+	msg, err = Sign(&Note{Text: text, Sigs: []Signature{{Name: "PeterNeumann", Hash: 0xc74f20a3, Base64: "BADSIGN="}}}, signer)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(msg) != want {
+		t.Errorf("Sign replacing signature: wrong output\nhave:\n%s\nwant:\n%s", msg, want)
+	}
+
+	// Check various bad inputs.
+	_, err = Sign(&Note{Text: "abc"}, signer)
+	if err == nil || err.Error() != "malformed note" {
+		t.Fatalf("Sign with short text: %v, want malformed note error", err)
+	}
+
+	_, err = Sign(&Note{Text: text, Sigs: []Signature{{Name: "a+b", Base64: "ABCD"}}})
+	if err == nil || err.Error() != "malformed note" {
+		t.Fatalf("Sign with bad name: %v, want malformed note error", err)
+	}
+
+	_, err = Sign(&Note{Text: text, Sigs: []Signature{{Name: "PeterNeumann", Hash: 0xc74f20a3, Base64: "BADHASH="}}})
+	if err == nil || err.Error() != "malformed note" {
+		t.Fatalf("Sign with bad pre-filled signature: %v, want malformed note error", err)
+	}
+
+	_, err = Sign(&Note{Text: text}, &badSigner{signer})
+	if err == nil || err.Error() != "invalid signer" {
+		t.Fatalf("Sign with bad signer: %v, want invalid signer error", err)
+	}
+
+	_, err = Sign(&Note{Text: text}, &errSigner{signer})
+	if err != errSurprise {
+		t.Fatalf("Sign with failing signer: %v, want errSurprise", err)
+	}
+}
+
+func TestVerifierList(t *testing.T) {
+	peterKey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	peterVerifier, err := NewVerifier(peterKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	enochKey := "EnochRoot+af0cfe78+ATtqJ7zOtqQtYqOo0CpvDXNlMhV3HeJDpjrASKGLWdop"
+	enochVerifier, err := NewVerifier(enochKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	list := VerifierList(peterVerifier, enochVerifier, enochVerifier)
+	v, err := list.Verifier("PeterNeumann", 0xc74f20a3)
+	if v != peterVerifier || err != nil {
+		t.Fatalf("list.Verifier(peter) = %v, %v, want %v, nil", v, err, peterVerifier)
+	}
+	v, err = list.Verifier("PeterNeumann", 0xc74f20a4)
+	if v != nil || err == nil || err.Error() != "unknown key PeterNeumann+c74f20a4" {
+		t.Fatalf("list.Verifier(peter bad hash) = %v, %v, want nil, unknown key error", v, err)
+	}
+
+	v, err = list.Verifier("PeterNeuman", 0xc74f20a3)
+	if v != nil || err == nil || err.Error() != "unknown key PeterNeuman+c74f20a3" {
+		t.Fatalf("list.Verifier(peter bad name) = %v, %v, want nil, unknown key error", v, err)
+	}
+	v, err = list.Verifier("EnochRoot", 0xaf0cfe78)
+	if v != nil || err == nil || err.Error() != "ambiguous key EnochRoot+af0cfe78" {
+		t.Fatalf("list.Verifier(enoch) = %v, %v, want nil, ambiguous key error", v, err)
+	}
+}
+
+type badSigner struct {
+	Signer
+}
+
+func (b *badSigner) Name() string {
+	return "bad name"
+}
+
+var errSurprise = errors.New("surprise!")
+
+type errSigner struct {
+	Signer
+}
+
+func (e *errSigner) Sign([]byte) ([]byte, error) {
+	return nil, errSurprise
+}
+
+type fixedVerifier struct{ v Verifier }
+
+func (v fixedVerifier) Verifier(name string, hash uint32) (Verifier, error) {
+	return v.v, nil
+}
+
+func TestOpen(t *testing.T) {
+	peterKey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	peterVerifier, err := NewVerifier(peterKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	enochKey := "EnochRoot+af0cfe78+ATtqJ7zOtqQtYqOo0CpvDXNlMhV3HeJDpjrASKGLWdop"
+	enochVerifier, err := NewVerifier(enochKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	text := `If you think cryptography is the answer to your problem,
+then you don't know what your problem is.
+`
+	peterSig := "— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n"
+	enochSig := "— EnochRoot rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ=\n"
+
+	peter := Signature{"PeterNeumann", 0xc74f20a3, "x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM="}
+	enoch := Signature{"EnochRoot", 0xaf0cfe78, "rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ="}
+
+	// Check one signature verified, one not.
+	n, err := Open([]byte(text+"\n"+peterSig+enochSig), VerifierList(peterVerifier))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n.Text != text {
+		t.Errorf("n.Text = %q, want %q", n.Text, text)
+	}
+	if len(n.Sigs) != 1 || n.Sigs[0] != peter {
+		t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter})
+	}
+	if len(n.UnverifiedSigs) != 1 || n.UnverifiedSigs[0] != enoch {
+		t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter})
+	}
+
+	// Check both verified.
+	n, err = Open([]byte(text+"\n"+peterSig+enochSig), VerifierList(peterVerifier, enochVerifier))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(n.Sigs) != 2 || n.Sigs[0] != peter || n.Sigs[1] != enoch {
+		t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter, enoch})
+	}
+	if len(n.UnverifiedSigs) != 0 {
+		t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.Sigs, []Signature{})
+	}
+
+	// Check both unverified.
+	n, err = Open([]byte(text+"\n"+peterSig+enochSig), VerifierList())
+	if n != nil || err == nil {
+		t.Fatalf("Open unverified = %v, %v, want nil, error", n, err)
+	}
+	e, ok := err.(*UnverifiedNoteError)
+	if !ok {
+		t.Fatalf("Open unverified: err is %T, want *UnverifiedNoteError", err)
+	}
+	if err.Error() != "note has no verifiable signatures" {
+		t.Fatalf("Open unverified: err.Error() = %q, want %q", err.Error(), "note has no verifiable signatures")
+	}
+
+	n = e.Note
+	if n == nil {
+		t.Fatalf("Open unverified: missing note in UnverifiedNoteError")
+	}
+	if len(n.Sigs) != 0 {
+		t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{})
+	}
+	if len(n.UnverifiedSigs) != 2 || n.UnverifiedSigs[0] != peter || n.UnverifiedSigs[1] != enoch {
+		t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter, enoch})
+	}
+
+	// Check duplicated verifier.
+	_, err = Open([]byte(text+"\n"+enochSig), VerifierList(enochVerifier, peterVerifier, enochVerifier))
+	if err == nil || err.Error() != "ambiguous key EnochRoot+af0cfe78" {
+		t.Fatalf("Open with duplicated verifier: err=%v, want ambiguous key", err)
+	}
+
+	// Check unused duplicated verifier.
+	_, err = Open([]byte(text+"\n"+peterSig), VerifierList(enochVerifier, peterVerifier, enochVerifier))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Check too many signatures.
+	n, err = Open([]byte(text+"\n"+strings.Repeat(peterSig, 101)), VerifierList(peterVerifier))
+	if n != nil || err == nil || err.Error() != "malformed note" {
+		t.Fatalf("Open too many verified signatures = %v, %v, want nil, malformed note error", n, err)
+	}
+	n, err = Open([]byte(text+"\n"+strings.Repeat(peterSig, 101)), VerifierList())
+	if n != nil || err == nil || err.Error() != "malformed note" {
+		t.Fatalf("Open too many verified signatures = %v, %v, want nil, malformed note error", n, err)
+	}
+
+	// Invalid signature.
+	n, err = Open([]byte(text+"\n"+peterSig[:60]+"ABCD"+peterSig[60:]), VerifierList(peterVerifier))
+	if n != nil || err == nil || err.Error() != "invalid signature for key PeterNeumann+c74f20a3" {
+		t.Fatalf("Open too many verified signatures = %v, %v, want nil, invalid signature error", n, err)
+	}
+
+	// Duplicated verified and unverified signatures.
+	enochABCD := Signature{"EnochRoot", 0xaf0cfe78, "rwz+eBzmZa0SO3NbfRGzPCpDckykFXSdeX+MNtCOXm2/5n" + "ABCD" + "2tiOHp+vAF1aGrQ5ovTG01oOTGwnWLox33WWd1RvMc+QQ="}
+	n, err = Open([]byte(text+"\n"+peterSig+peterSig+enochSig+enochSig+enochSig[:60]+"ABCD"+enochSig[60:]), VerifierList(peterVerifier))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(n.Sigs) != 1 || n.Sigs[0] != peter {
+		t.Errorf("n.Sigs:\nhave %v\nwant %v", n.Sigs, []Signature{peter})
+	}
+	if len(n.UnverifiedSigs) != 2 || n.UnverifiedSigs[0] != enoch || n.UnverifiedSigs[1] != enochABCD {
+		t.Errorf("n.UnverifiedSigs:\nhave %v\nwant %v", n.UnverifiedSigs, []Signature{enoch, enochABCD})
+	}
+
+	// Invalid encoded message syntax.
+	badMsgs := []string{
+		text,
+		text + "\n",
+		text + "\n" + peterSig[:len(peterSig)-1],
+		"\x01" + text + "\n" + peterSig,
+		"\xff" + text + "\n" + peterSig,
+		text + "\n" + "— Bad Name x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=",
+		text + "\n" + peterSig + "Unexpected line.\n",
+	}
+	for _, msg := range badMsgs {
+		n, err := Open([]byte(msg), VerifierList(peterVerifier))
+		if n != nil || err == nil || err.Error() != "malformed note" {
+			t.Fatalf("Open bad msg = %v, %v, want nil, malformed note error\nmsg:\n%s", n, err, msg)
+		}
+	}
+
+	// Verifiers returns a Verifier for the wrong name or hash.
+	misnamedSig := strings.Replace(peterSig, "PeterNeumann", "CarmenSandiego", -1)
+	_, err = Open([]byte(text+"\n"+misnamedSig), fixedVerifier{peterVerifier})
+	if err != errMismatchedVerifier {
+		t.Fatalf("Open with wrong Verifier, err=%v, want errMismatchedVerifier", err)
+	}
+	wrongHash := strings.Replace(peterSig, "x08g", "xxxx", -1)
+	_, err = Open([]byte(text+"\n"+wrongHash), fixedVerifier{peterVerifier})
+	if err != errMismatchedVerifier {
+		t.Fatalf("Open with wrong Verifier, err=%v, want errMismatchedVerifier", err)
+	}
+}
+
+func BenchmarkOpen(b *testing.B) {
+	vkey := "PeterNeumann+c74f20a3+ARpc2QcUPDhMQegwxbzhKqiBfsVkmqq/LDE4izWy10TW"
+	msg := []byte("If you think cryptography is the answer to your problem,\n" +
+		"then you don't know what your problem is.\n" +
+		"\n" +
+		"— PeterNeumann x08go/ZJkuBS9UG/SffcvIAQxVBtiFupLLr8pAcElZInNIuGUgYN1FFYC2pZSNXgKvqfqdngotpRZb6KE6RyyBwJnAM=\n")
+
+	verifier, err := NewVerifier(vkey)
+	if err != nil {
+		b.Fatal(err)
+	}
+	verifiers := VerifierList(verifier)
+	verifiers0 := VerifierList()
+
+	// Try with 0 signatures and 1 signature so we can tell how much each signature adds.
+
+	b.Run("Sig0", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_, err := Open(msg, verifiers0)
+			e, ok := err.(*UnverifiedNoteError)
+			if !ok {
+				b.Fatal("expected UnverifiedNoteError")
+			}
+			n := e.Note
+			if len(n.Sigs) != 0 || len(n.UnverifiedSigs) != 1 {
+				b.Fatal("wrong signature count")
+			}
+		}
+	})
+
+	b.Run("Sig1", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			n, err := Open(msg, verifiers)
+			if err != nil {
+				b.Fatal(err)
+			}
+			if len(n.Sigs) != 1 || len(n.UnverifiedSigs) != 0 {
+				b.Fatal("wrong signature count")
+			}
+		}
+	})
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/server.go

@@ -0,0 +1,181 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package sumdb implements the HTTP protocols for serving or accessing a module checksum database.
+package sumdb
+
+import (
+	"context"
+	"net/http"
+	"os"
+	"strings"
+
+	"golang.org/x/mod/internal/lazyregexp"
+	"golang.org/x/mod/module"
+	"golang.org/x/mod/sumdb/tlog"
+)
+
+// A ServerOps provides the external operations
+// (underlying database access and so on) needed by the [Server].
+type ServerOps interface {
+	// Signed returns the signed hash of the latest tree.
+	Signed(ctx context.Context) ([]byte, error)
+
+	// ReadRecords returns the content for the n records id through id+n-1.
+	ReadRecords(ctx context.Context, id, n int64) ([][]byte, error)
+
+	// Lookup looks up a record for the given module,
+	// returning the record ID.
+	Lookup(ctx context.Context, m module.Version) (int64, error)
+
+	// ReadTileData reads the content of tile t.
+	// It is only invoked for hash tiles (t.L ≥ 0).
+	ReadTileData(ctx context.Context, t tlog.Tile) ([]byte, error)
+}
+
+// A Server is the checksum database HTTP server,
+// which implements http.Handler and should be invoked
+// to serve the paths listed in [ServerPaths].
+type Server struct {
+	ops ServerOps
+}
+
+// NewServer returns a new Server using the given operations.
+func NewServer(ops ServerOps) *Server {
+	return &Server{ops: ops}
+}
+
+// ServerPaths are the URL paths the Server can (and should) serve.
+//
+// Typically a server will do:
+//
+//	srv := sumdb.NewServer(ops)
+//	for _, path := range sumdb.ServerPaths {
+//		http.Handle(path, srv)
+//	}
+var ServerPaths = []string{
+	"/lookup/",
+	"/latest",
+	"/tile/",
+}
+
+var modVerRE = lazyregexp.New(`^[^@]+@v[0-9]+\.[0-9]+\.[0-9]+(-[^@]*)?(\+incompatible)?$`)
+
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+
+	switch {
+	default:
+		http.NotFound(w, r)
+
+	case strings.HasPrefix(r.URL.Path, "/lookup/"):
+		mod := strings.TrimPrefix(r.URL.Path, "/lookup/")
+		if !modVerRE.MatchString(mod) {
+			http.Error(w, "invalid module@version syntax", http.StatusBadRequest)
+			return
+		}
+		i := strings.Index(mod, "@")
+		escPath, escVers := mod[:i], mod[i+1:]
+		path, err := module.UnescapePath(escPath)
+		if err != nil {
+			reportError(w, err)
+			return
+		}
+		vers, err := module.UnescapeVersion(escVers)
+		if err != nil {
+			reportError(w, err)
+			return
+		}
+		id, err := s.ops.Lookup(ctx, module.Version{Path: path, Version: vers})
+		if err != nil {
+			reportError(w, err)
+			return
+		}
+		records, err := s.ops.ReadRecords(ctx, id, 1)
+		if err != nil {
+			// This should never happen - the lookup says the record exists.
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		if len(records) != 1 {
+			http.Error(w, "invalid record count returned by ReadRecords", http.StatusInternalServerError)
+			return
+		}
+		msg, err := tlog.FormatRecord(id, records[0])
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		signed, err := s.ops.Signed(ctx)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
+		w.Write(msg)
+		w.Write(signed)
+
+	case r.URL.Path == "/latest":
+		data, err := s.ops.Signed(ctx)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
+		w.Write(data)
+
+	case strings.HasPrefix(r.URL.Path, "/tile/"):
+		t, err := tlog.ParseTilePath(r.URL.Path[1:])
+		if err != nil {
+			http.Error(w, "invalid tile syntax", http.StatusBadRequest)
+			return
+		}
+		if t.L == -1 {
+			// Record data.
+			start := t.N << uint(t.H)
+			records, err := s.ops.ReadRecords(ctx, start, int64(t.W))
+			if err != nil {
+				reportError(w, err)
+				return
+			}
+			if len(records) != t.W {
+				http.Error(w, "invalid record count returned by ReadRecords", http.StatusInternalServerError)
+				return
+			}
+			var data []byte
+			for i, text := range records {
+				msg, err := tlog.FormatRecord(start+int64(i), text)
+				if err != nil {
+					http.Error(w, err.Error(), http.StatusInternalServerError)
+					return
+				}
+				data = append(data, msg...)
+			}
+			w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
+			w.Write(data)
+			return
+		}
+
+		data, err := s.ops.ReadTileData(ctx, t)
+		if err != nil {
+			reportError(w, err)
+			return
+		}
+		w.Header().Set("Content-Type", "application/octet-stream")
+		w.Write(data)
+	}
+}
+
+// reportError reports err to w.
+// If it's a not-found, the reported error is 404.
+// Otherwise it is an internal server error.
+// The caller must only call reportError in contexts where
+// a not-found err should be reported as 404.
+func reportError(w http.ResponseWriter, err error) {
+	if os.IsNotExist(err) {
+		http.Error(w, err.Error(), http.StatusNotFound)
+		return
+	}
+	http.Error(w, err.Error(), http.StatusInternalServerError)
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/storage/mem.go

@@ -0,0 +1,114 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package storage
+
+import (
+	"context"
+	"errors"
+	"math/rand"
+	"sync"
+)
+
+// Mem is an in-memory implementation of [Storage].
+// It is meant for tests and does not store any data to persistent storage.
+//
+// The zero value is an empty Mem ready for use.
+type Mem struct {
+	mu    sync.RWMutex
+	table map[string]string
+}
+
+// A memTx is a transaction in a Mem.
+type memTx struct {
+	m      *Mem
+	writes []Write
+}
+
+// errRetry is an internal sentinel indicating that the transaction should be retried.
+// It is never returned to the caller.
+var errRetry = errors.New("retry")
+
+// ReadOnly runs f in a read-only transaction.
+func (m *Mem) ReadOnly(ctx context.Context, f func(context.Context, Transaction) error) error {
+	tx := &memTx{m: m}
+	for {
+		err := func() error {
+			m.mu.Lock()
+			defer m.mu.Unlock()
+
+			if err := f(ctx, tx); err != nil {
+				return err
+			}
+			// Spurious retry with 10% probability.
+			if rand.Intn(10) == 0 {
+				return errRetry
+			}
+			return nil
+		}()
+		if err != errRetry {
+			return err
+		}
+	}
+}
+
+// ReadWrite runs f in a read-write transaction.
+func (m *Mem) ReadWrite(ctx context.Context, f func(context.Context, Transaction) error) error {
+	tx := &memTx{m: m}
+	for {
+		err := func() error {
+			m.mu.Lock()
+			defer m.mu.Unlock()
+
+			tx.writes = []Write{}
+			if err := f(ctx, tx); err != nil {
+				return err
+			}
+			// Spurious retry with 10% probability.
+			if rand.Intn(10) == 0 {
+				return errRetry
+			}
+			if m.table == nil {
+				m.table = make(map[string]string)
+			}
+			for _, w := range tx.writes {
+				if w.Value == "" {
+					delete(m.table, w.Key)
+				} else {
+					m.table[w.Key] = w.Value
+				}
+			}
+			return nil
+		}()
+		if err != errRetry {
+			return err
+		}
+	}
+}
+
+// ReadValues returns the values associated with the given keys.
+func (tx *memTx) ReadValues(ctx context.Context, keys []string) ([]string, error) {
+	vals := make([]string, len(keys))
+	for i, key := range keys {
+		vals[i] = tx.m.table[key]
+	}
+	return vals, nil
+}
+
+// ReadValue returns the value associated with the single key.
+func (tx *memTx) ReadValue(ctx context.Context, key string) (string, error) {
+	return tx.m.table[key], nil
+}
+
+// BufferWrites buffers a list of writes to be applied
+// to the table when the transaction commits.
+// The changes are not visible to reads within the transaction.
+// The map argument is not used after the call returns.
+func (tx *memTx) BufferWrites(list []Write) error {
+	if tx.writes == nil {
+		panic("BufferWrite on read-only transaction")
+	}
+	tx.writes = append(tx.writes, list...)
+	return nil
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/storage/mem_test.go

@@ -0,0 +1,14 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package storage
+
+import (
+	"context"
+	"testing"
+)
+
+func TestMem(t *testing.T) {
+	TestStorage(t, context.Background(), new(Mem))
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/storage/storage.go

@@ -0,0 +1,56 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package storage defines storage interfaces for and a basic implementation of a checksum database.
+package storage
+
+import "context"
+
+// A Storage is a transaction key-value storage system.
+type Storage interface {
+	// ReadOnly runs f in a read-only transaction.
+	// It is equivalent to ReadWrite except that the
+	// transaction's BufferWrite method will fail unconditionally.
+	// (The implementation may be able to optimize the
+	// transaction if it knows at the start that no writes will happen.)
+	ReadOnly(ctx context.Context, f func(context.Context, Transaction) error) error
+
+	// ReadWrite runs f in a read-write transaction.
+	// If f returns an error, the transaction aborts and returns that error.
+	// If f returns nil, the transaction attempts to commit and then return nil.
+	// Otherwise it tries again. Note that f may be called multiple times and that
+	// the result only describes the effect of the final call to f.
+	// The caller must take care not to use any state computed during
+	// earlier calls to f, or even the last call to f when an error is returned.
+	ReadWrite(ctx context.Context, f func(context.Context, Transaction) error) error
+}
+
+// A Transaction provides read and write operations within a transaction,
+// as executed by [Storage]'s ReadOnly or ReadWrite methods.
+type Transaction interface {
+	// ReadValue reads the value associated with a single key.
+	// If there is no value associated with that key, ReadKey returns an empty value.
+	// An error is only returned for problems accessing the storage.
+	ReadValue(ctx context.Context, key string) (value string, err error)
+
+	// ReadValues reads the values associated with the given keys.
+	// If there is no value stored for a given key, ReadValues returns an empty value for that key.
+	// An error is only returned for problems accessing the storage.
+	ReadValues(ctx context.Context, keys []string) (values []string, err error)
+
+	// BufferWrites buffers the given writes,
+	// to be applied at the end of the transaction.
+	// BufferWrites panics if this is a ReadOnly transaction.
+	// It returns an error if it detects any other problems.
+	// The behavior of multiple writes buffered using the same key
+	// is undefined: it may return an error or not.
+	BufferWrites(writes []Write) error
+}
+
+// A Write is a single change to be applied at the end of a read-write transaction.
+// A Write with an empty value deletes the value associated with the given key.
+type Write struct {
+	Key   string
+	Value string
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/storage/test.go

@@ -0,0 +1,75 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package storage
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"testing"
+)
+
+// TestStorage tests a Storage implementation.
+func TestStorage(t *testing.T, ctx context.Context, storage Storage) {
+	s := storage
+
+	// Insert records.
+	err := s.ReadWrite(ctx, func(ctx context.Context, tx Transaction) error {
+		for i := 0; i < 10; i++ {
+			err := tx.BufferWrites([]Write{
+				{Key: fmt.Sprint(i), Value: fmt.Sprint(-i)},
+				{Key: fmt.Sprint(1000 + i), Value: fmt.Sprint(-1000 - i)},
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Read the records back.
+	testRead := func() {
+		err := s.ReadOnly(ctx, func(ctx context.Context, tx Transaction) error {
+			for i := int64(0); i < 1010; i++ {
+				if i == 10 {
+					i = 1000
+				}
+				val, err := tx.ReadValue(ctx, fmt.Sprint(i))
+				if err != nil {
+					t.Fatalf("reading %v: %v", i, err)
+				}
+				if want := fmt.Sprint(-i); val != want {
+					t.Fatalf("ReadValue %v = %q, want %v", i, val, want)
+				}
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	testRead()
+
+	// Buffered writes in failed transaction should not be applied.
+	err = s.ReadWrite(ctx, func(ctx context.Context, tx Transaction) error {
+		tx.BufferWrites([]Write{
+			{Key: fmt.Sprint(0), Value: ""},          // delete
+			{Key: fmt.Sprint(1), Value: "overwrite"}, // overwrite
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		return io.ErrUnexpectedEOF
+	})
+	if err != io.ErrUnexpectedEOF {
+		t.Fatalf("ReadWrite returned %v, want ErrUnexpectedEOF", err)
+	}
+
+	// All same values should still be there.
+	testRead()
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/test.go

@@ -0,0 +1,124 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sumdb
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"golang.org/x/mod/module"
+	"golang.org/x/mod/sumdb/note"
+	"golang.org/x/mod/sumdb/tlog"
+)
+
+// NewTestServer constructs a new [TestServer]
+// that will sign its tree with the given signer key
+// (see [golang.org/x/mod/sumdb/note])
+// and fetch new records as needed by calling gosum.
+func NewTestServer(signer string, gosum func(path, vers string) ([]byte, error)) *TestServer {
+	return &TestServer{signer: signer, gosum: gosum}
+}
+
+// A TestServer is an in-memory implementation of [ServerOps] for testing.
+type TestServer struct {
+	signer string
+	gosum  func(path, vers string) ([]byte, error)
+
+	mu      sync.Mutex
+	hashes  testHashes
+	records [][]byte
+	lookup  map[string]int64
+}
+
+// testHashes implements tlog.HashReader, reading from a slice.
+type testHashes []tlog.Hash
+
+func (h testHashes) ReadHashes(indexes []int64) ([]tlog.Hash, error) {
+	var list []tlog.Hash
+	for _, id := range indexes {
+		list = append(list, h[id])
+	}
+	return list, nil
+}
+
+func (s *TestServer) Signed(ctx context.Context) ([]byte, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	size := int64(len(s.records))
+	h, err := tlog.TreeHash(size, s.hashes)
+	if err != nil {
+		return nil, err
+	}
+	text := tlog.FormatTree(tlog.Tree{N: size, Hash: h})
+	signer, err := note.NewSigner(s.signer)
+	if err != nil {
+		return nil, err
+	}
+	return note.Sign(&note.Note{Text: string(text)}, signer)
+}
+
+func (s *TestServer) ReadRecords(ctx context.Context, id, n int64) ([][]byte, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	var list [][]byte
+	for i := int64(0); i < n; i++ {
+		if id+i >= int64(len(s.records)) {
+			return nil, fmt.Errorf("missing records")
+		}
+		list = append(list, s.records[id+i])
+	}
+	return list, nil
+}
+
+func (s *TestServer) Lookup(ctx context.Context, m module.Version) (int64, error) {
+	key := m.String()
+	s.mu.Lock()
+	id, ok := s.lookup[key]
+	s.mu.Unlock()
+	if ok {
+		return id, nil
+	}
+
+	// Look up module and compute go.sum lines.
+	data, err := s.gosum(m.Path, m.Version)
+	if err != nil {
+		return 0, err
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// We ran the fetch without the lock.
+	// If another fetch happened and committed, use it instead.
+	id, ok = s.lookup[key]
+	if ok {
+		return id, nil
+	}
+
+	// Add record.
+	id = int64(len(s.records))
+	s.records = append(s.records, data)
+	if s.lookup == nil {
+		s.lookup = make(map[string]int64)
+	}
+	s.lookup[key] = id
+	hashes, err := tlog.StoredHashesForRecordHash(id, tlog.RecordHash(data), s.hashes)
+	if err != nil {
+		panic(err)
+	}
+	s.hashes = append(s.hashes, hashes...)
+
+	return id, nil
+}
+
+func (s *TestServer) ReadTileData(ctx context.Context, t tlog.Tile) ([]byte, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	return tlog.ReadTileData(t, s.hashes)
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/ct_test.go

@@ -0,0 +1,96 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tlog
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"testing"
+)
+
+func TestCertificateTransparency(t *testing.T) {
+	// Test that we can verify actual Certificate Transparency proofs.
+	// (The other tests check that we can verify our own proofs;
+	// this is a test that the two are compatible.)
+
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+
+	var root ctTree
+	httpGET(t, "http://ct.googleapis.com/logs/argon2020/ct/v1/get-sth", &root)
+
+	var leaf ctEntries
+	httpGET(t, "http://ct.googleapis.com/logs/argon2020/ct/v1/get-entries?start=10000&end=10000", &leaf)
+	hash := RecordHash(leaf.Entries[0].Data)
+
+	var rp ctRecordProof
+	httpGET(t, "http://ct.googleapis.com/logs/argon2020/ct/v1/get-proof-by-hash?tree_size="+fmt.Sprint(root.Size)+"&hash="+url.QueryEscape(hash.String()), &rp)
+
+	err := CheckRecord(rp.Proof, root.Size, root.Hash, 10000, hash)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var tp ctTreeProof
+	httpGET(t, "http://ct.googleapis.com/logs/argon2020/ct/v1/get-sth-consistency?first=3654490&second="+fmt.Sprint(root.Size), &tp)
+
+	oh, _ := ParseHash("AuIZ5V6sDUj1vn3Y1K85oOaQ7y+FJJKtyRTl1edIKBQ=")
+	err = CheckTree(tp.Proof, root.Size, root.Hash, 3654490, oh)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+type ctTree struct {
+	Size int64 `json:"tree_size"`
+	Hash Hash  `json:"sha256_root_hash"`
+}
+
+type ctEntries struct {
+	Entries []*ctEntry
+}
+
+type ctEntry struct {
+	Data []byte `json:"leaf_input"`
+}
+
+type ctRecordProof struct {
+	Index int64       `json:"leaf_index"`
+	Proof RecordProof `json:"audit_path"`
+}
+
+type ctTreeProof struct {
+	Proof TreeProof `json:"consistency"`
+}
+
+func httpGET(t *testing.T, url string, targ interface{}) {
+	if testing.Verbose() {
+		println()
+		println(url)
+	}
+	resp, err := http.Get(url)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if testing.Verbose() {
+		os.Stdout.Write(data)
+	}
+	err = json.Unmarshal(data, targ)
+	if err != nil {
+		println(url)
+		os.Stdout.Write(data)
+		t.Fatal(err)
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/note.go

@@ -0,0 +1,135 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tlog
+
+import (
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"unicode/utf8"
+)
+
+// A Tree is a tree description, to be signed by a go.sum database server.
+type Tree struct {
+	N    int64
+	Hash Hash
+}
+
+// FormatTree formats a tree description for inclusion in a note.
+//
+// The encoded form is three lines, each ending in a newline (U+000A):
+//
+//	go.sum database tree
+//	N
+//	Hash
+//
+// where N is in decimal and Hash is in base64.
+//
+// A future backwards-compatible encoding may add additional lines,
+// which the parser can ignore.
+// A future backwards-incompatible encoding would use a different
+// first line (for example, "go.sum database tree v2").
+func FormatTree(tree Tree) []byte {
+	return []byte(fmt.Sprintf("go.sum database tree\n%d\n%s\n", tree.N, tree.Hash))
+}
+
+var errMalformedTree = errors.New("malformed tree note")
+var treePrefix = []byte("go.sum database tree\n")
+
+// ParseTree parses a formatted tree root description.
+func ParseTree(text []byte) (tree Tree, err error) {
+	// The message looks like:
+	//
+	//	go.sum database tree
+	//	2
+	//	nND/nri/U0xuHUrYSy0HtMeal2vzD9V4k/BO79C+QeI=
+	//
+	// For forwards compatibility, extra text lines after the encoding are ignored.
+	if !bytes.HasPrefix(text, treePrefix) || bytes.Count(text, []byte("\n")) < 3 || len(text) > 1e6 {
+		return Tree{}, errMalformedTree
+	}
+
+	lines := strings.SplitN(string(text), "\n", 4)
+	n, err := strconv.ParseInt(lines[1], 10, 64)
+	if err != nil || n < 0 || lines[1] != strconv.FormatInt(n, 10) {
+		return Tree{}, errMalformedTree
+	}
+
+	h, err := base64.StdEncoding.DecodeString(lines[2])
+	if err != nil || len(h) != HashSize {
+		return Tree{}, errMalformedTree
+	}
+
+	var hash Hash
+	copy(hash[:], h)
+	return Tree{n, hash}, nil
+}
+
+var errMalformedRecord = errors.New("malformed record data")
+
+// FormatRecord formats a record for serving to a client
+// in a lookup response or data tile.
+//
+// The encoded form is the record ID as a single number,
+// then the text of the record, and then a terminating blank line.
+// Record text must be valid UTF-8 and must not contain any ASCII control
+// characters (those below U+0020) other than newline (U+000A).
+// It must end in a terminating newline and not contain any blank lines.
+func FormatRecord(id int64, text []byte) (msg []byte, err error) {
+	if !isValidRecordText(text) {
+		return nil, errMalformedRecord
+	}
+	msg = []byte(fmt.Sprintf("%d\n", id))
+	msg = append(msg, text...)
+	msg = append(msg, '\n')
+	return msg, nil
+}
+
+// isValidRecordText reports whether text is syntactically valid record text.
+func isValidRecordText(text []byte) bool {
+	var last rune
+	for i := 0; i < len(text); {
+		r, size := utf8.DecodeRune(text[i:])
+		if r < 0x20 && r != '\n' || r == utf8.RuneError && size == 1 || last == '\n' && r == '\n' {
+			return false
+		}
+		i += size
+		last = r
+	}
+	if last != '\n' {
+		return false
+	}
+	return true
+}
+
+// ParseRecord parses a record description at the start of text,
+// stopping immediately after the terminating blank line.
+// It returns the record id, the record text, and the remainder of text.
+func ParseRecord(msg []byte) (id int64, text, rest []byte, err error) {
+	// Leading record id.
+	i := bytes.IndexByte(msg, '\n')
+	if i < 0 {
+		return 0, nil, nil, errMalformedRecord
+	}
+	id, err = strconv.ParseInt(string(msg[:i]), 10, 64)
+	if err != nil {
+		return 0, nil, nil, errMalformedRecord
+	}
+	msg = msg[i+1:]
+
+	// Record text.
+	i = bytes.Index(msg, []byte("\n\n"))
+	if i < 0 {
+		return 0, nil, nil, errMalformedRecord
+	}
+	text, rest = msg[:i+1], msg[i+2:]
+	if !isValidRecordText(text) {
+		return 0, nil, nil, errMalformedRecord
+	}
+	return id, text, rest, nil
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/note_test.go

@@ -0,0 +1,133 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tlog
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestFormatTree(t *testing.T) {
+	n := int64(123456789012)
+	h := RecordHash([]byte("hello world"))
+	golden := "go.sum database tree\n123456789012\nTszzRgjTG6xce+z2AG31kAXYKBgQVtCSCE40HmuwBb0=\n"
+	b := FormatTree(Tree{n, h})
+	if string(b) != golden {
+		t.Errorf("FormatTree(...) = %q, want %q", b, golden)
+	}
+}
+
+func TestParseTree(t *testing.T) {
+	in := "go.sum database tree\n123456789012\nTszzRgjTG6xce+z2AG31kAXYKBgQVtCSCE40HmuwBb0=\n"
+	goldH := RecordHash([]byte("hello world"))
+	goldN := int64(123456789012)
+	tree, err := ParseTree([]byte(in))
+	if tree.N != goldN || tree.Hash != goldH || err != nil {
+		t.Fatalf("ParseTree(...) = Tree{%d, %v}, %v, want Tree{%d, %v}, nil", tree.N, tree.Hash, err, goldN, goldH)
+	}
+
+	// Check invalid trees.
+	var badTrees = []string{
+		"not-" + in,
+		"go.sum database tree\n0xabcdef\nTszzRgjTG6xce+z2AG31kAXYKBgQVtCSCE40HmuwBb0=\n",
+		"go.sum database tree\n123456789012\nTszzRgjTG6xce+z2AG31kAXYKBgQVtCSCE40HmuwBTOOBIG=\n",
+	}
+	for _, bad := range badTrees {
+		_, err := ParseTree([]byte(bad))
+		if err == nil {
+			t.Fatalf("ParseTree(%q) succeeded, want failure", in)
+		}
+	}
+
+	// Check junk on end is ignored.
+	var goodTrees = []string{
+		in + "JOE",
+		in + "JOE\n",
+		in + strings.Repeat("JOE\n", 1000),
+	}
+	for _, good := range goodTrees {
+		_, err := ParseTree([]byte(good))
+		if tree.N != goldN || tree.Hash != goldH || err != nil {
+			t.Fatalf("ParseTree(...+%q) = Tree{%d, %v}, %v, want Tree{%d, %v}, nil", good[len(in):], tree.N, tree.Hash, err, goldN, goldH)
+		}
+	}
+}
+
+func TestFormatRecord(t *testing.T) {
+	id := int64(123456789012)
+	text := "hello, world\n"
+	golden := "123456789012\nhello, world\n\n"
+	msg, err := FormatRecord(id, []byte(text))
+	if err != nil {
+		t.Fatalf("FormatRecord: %v", err)
+	}
+	if string(msg) != golden {
+		t.Fatalf("FormatRecord(...) = %q, want %q", msg, golden)
+	}
+
+	var badTexts = []string{
+		"",
+		"hello\nworld",
+		"hello\n\nworld\n",
+		"hello\x01world\n",
+	}
+	for _, bad := range badTexts {
+		msg, err := FormatRecord(id, []byte(bad))
+		if err == nil {
+			t.Errorf("FormatRecord(id, %q) = %q, want error", bad, msg)
+		}
+	}
+}
+
+func TestParseRecord(t *testing.T) {
+	in := "123456789012\nhello, world\n\njunk on end\x01\xff"
+	goldID := int64(123456789012)
+	goldText := "hello, world\n"
+	goldRest := "junk on end\x01\xff"
+	id, text, rest, err := ParseRecord([]byte(in))
+	if id != goldID || string(text) != goldText || string(rest) != goldRest || err != nil {
+		t.Fatalf("ParseRecord(%q) = %d, %q, %q, %v, want %d, %q, %q, nil", in, id, text, rest, err, goldID, goldText, goldRest)
+	}
+
+	in = "123456789012\nhello, world\n\n"
+	id, text, rest, err = ParseRecord([]byte(in))
+	if id != goldID || string(text) != goldText || len(rest) != 0 || err != nil {
+		t.Fatalf("ParseRecord(%q) = %d, %q, %q, %v, want %d, %q, %q, nil", in, id, text, rest, err, goldID, goldText, "")
+	}
+	if rest == nil {
+		t.Fatalf("ParseRecord(%q): rest = []byte(nil), want []byte{}", in)
+	}
+
+	// Check invalid records.
+	var badRecords = []string{
+		"not-" + in,
+		"123\nhello\x01world\n\n",
+		"123\nhello\xffworld\n\n",
+		"123\nhello world\n",
+		"0x123\nhello world\n\n",
+	}
+	for _, bad := range badRecords {
+		id, text, rest, err := ParseRecord([]byte(bad))
+		if err == nil {
+			t.Fatalf("ParseRecord(%q) = %d, %q, %q, nil, want error", in, id, text, rest)
+		}
+	}
+}
+
+// FuzzParseTree tests that ParseTree never crashes
+func FuzzParseTree(f *testing.F) {
+	f.Add([]byte("go.sum database tree\n123456789012\nTszzRgjTG6xce+z2AG31kAXYKBgQVtCSCE40HmuwBb0=\n"))
+	f.Fuzz(func(t *testing.T, text []byte) {
+		ParseTree(text)
+	})
+}
+
+// FuzzParseRecord tests that ParseRecord never crashes
+func FuzzParseRecord(f *testing.F) {
+	f.Add([]byte("12345\nhello\n\n"))
+	f.Fuzz(func(t *testing.T, msg []byte) {
+		ParseRecord(msg)
+	})
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/tile.go

@@ -0,0 +1,435 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tlog
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// A Tile is a description of a transparency log tile.
+// A tile of height H at level L offset N lists W consecutive hashes
+// at level H*L of the tree starting at offset N*(2**H).
+// A complete tile lists 2**H hashes; a partial tile lists fewer.
+// Note that a tile represents the entire subtree of height H
+// with those hashes as the leaves. The levels above H*L
+// can be reconstructed by hashing the leaves.
+//
+// Each Tile can be encoded as a “tile coordinate path”
+// of the form tile/H/L/NNN[.p/W].
+// The .p/W suffix is present only for partial tiles, meaning W < 2**H.
+// The NNN element is an encoding of N into 3-digit path elements.
+// All but the last path element begins with an "x".
+// For example,
+// Tile{H: 3, L: 4, N: 1234067, W: 1}'s path
+// is tile/3/4/x001/x234/067.p/1, and
+// Tile{H: 3, L: 4, N: 1234067, W: 8}'s path
+// is tile/3/4/x001/x234/067.
+// See the [Tile.Path] method and the [ParseTilePath] function.
+//
+// The special level L=-1 holds raw record data instead of hashes.
+// In this case, the level encodes into a tile path as the path element
+// "data" instead of "-1".
+//
+// See also https://golang.org/design/25530-sumdb#checksum-database
+// and https://research.swtch.com/tlog#tiling_a_log.
+type Tile struct {
+	H int   // height of tile (1 ≤ H ≤ 30)
+	L int   // level in tiling (-1 ≤ L ≤ 63)
+	N int64 // number within level (0 ≤ N, unbounded)
+	W int   // width of tile (1 ≤ W ≤ 2**H; 2**H is complete tile)
+}
+
+// TileForIndex returns the tile of fixed height h ≥ 1
+// and least width storing the given hash storage index.
+//
+// If h ≤ 0, [TileForIndex] panics.
+func TileForIndex(h int, index int64) Tile {
+	if h <= 0 {
+		panic(fmt.Sprintf("TileForIndex: invalid height %d", h))
+	}
+	t, _, _ := tileForIndex(h, index)
+	return t
+}
+
+// tileForIndex returns the tile of height h ≥ 1
+// storing the given hash index, which can be
+// reconstructed using tileHash(data[start:end]).
+func tileForIndex(h int, index int64) (t Tile, start, end int) {
+	level, n := SplitStoredHashIndex(index)
+	t.H = h
+	t.L = level / h
+	level -= t.L * h // now level within tile
+	t.N = n << uint(level) >> uint(t.H)
+	n -= t.N << uint(t.H) >> uint(level) // now n within tile at level
+	t.W = int((n + 1) << uint(level))
+	return t, int(n<<uint(level)) * HashSize, int((n+1)<<uint(level)) * HashSize
+}
+
+// HashFromTile returns the hash at the given storage index,
+// provided that t == TileForIndex(t.H, index) or a wider version,
+// and data is t's tile data (of length at least t.W*HashSize).
+func HashFromTile(t Tile, data []byte, index int64) (Hash, error) {
+	if t.H < 1 || t.H > 30 || t.L < 0 || t.L >= 64 || t.W < 1 || t.W > 1<<uint(t.H) {
+		return Hash{}, fmt.Errorf("invalid tile %v", t.Path())
+	}
+	if len(data) < t.W*HashSize {
+		return Hash{}, fmt.Errorf("data len %d too short for tile %v", len(data), t.Path())
+	}
+	t1, start, end := tileForIndex(t.H, index)
+	if t.L != t1.L || t.N != t1.N || t.W < t1.W {
+		return Hash{}, fmt.Errorf("index %v is in %v not %v", index, t1.Path(), t.Path())
+	}
+	return tileHash(data[start:end]), nil
+}
+
+// tileHash computes the subtree hash corresponding to the (2^K)-1 hashes in data.
+func tileHash(data []byte) Hash {
+	if len(data) == 0 {
+		panic("bad math in tileHash")
+	}
+	if len(data) == HashSize {
+		var h Hash
+		copy(h[:], data)
+		return h
+	}
+	n := len(data) / 2
+	return NodeHash(tileHash(data[:n]), tileHash(data[n:]))
+}
+
+// NewTiles returns the coordinates of the tiles of height h ≥ 1
+// that must be published when publishing from a tree of
+// size newTreeSize to replace a tree of size oldTreeSize.
+// (No tiles need to be published for a tree of size zero.)
+//
+// If h ≤ 0, NewTiles panics.
+func NewTiles(h int, oldTreeSize, newTreeSize int64) []Tile {
+	if h <= 0 {
+		panic(fmt.Sprintf("NewTiles: invalid height %d", h))
+	}
+	H := uint(h)
+	var tiles []Tile
+	for level := uint(0); newTreeSize>>(H*level) > 0; level++ {
+		oldN := oldTreeSize >> (H * level)
+		newN := newTreeSize >> (H * level)
+		for n := oldN >> H; n < newN>>H; n++ {
+			tiles = append(tiles, Tile{H: h, L: int(level), N: n, W: 1 << H})
+		}
+		n := newN >> H
+		maxW := int(newN - n<<H)
+		minW := 1
+		if oldN > n<<H {
+			minW = int(oldN - n<<H)
+		}
+		for w := minW; w <= maxW; w++ {
+			tiles = append(tiles, Tile{H: h, L: int(level), N: n, W: w})
+		}
+	}
+	return tiles
+}
+
+// ReadTileData reads the hashes for tile t from r
+// and returns the corresponding tile data.
+func ReadTileData(t Tile, r HashReader) ([]byte, error) {
+	size := t.W
+	if size == 0 {
+		size = 1 << uint(t.H)
+	}
+	start := t.N << uint(t.H)
+	indexes := make([]int64, size)
+	for i := 0; i < size; i++ {
+		indexes[i] = StoredHashIndex(t.H*t.L, start+int64(i))
+	}
+
+	hashes, err := r.ReadHashes(indexes)
+	if err != nil {
+		return nil, err
+	}
+	if len(hashes) != len(indexes) {
+		return nil, fmt.Errorf("tlog: ReadHashes(%d indexes) = %d hashes", len(indexes), len(hashes))
+	}
+
+	tile := make([]byte, size*HashSize)
+	for i := 0; i < size; i++ {
+		copy(tile[i*HashSize:], hashes[i][:])
+	}
+	return tile, nil
+}
+
+// To limit the size of any particular directory listing,
+// we encode the (possibly very large) number N
+// by encoding three digits at a time.
+// For example, 123456789 encodes as x123/x456/789.
+// Each directory has at most 1000 each xNNN, NNN, and NNN.p children,
+// so there are at most 3000 entries in any one directory.
+const pathBase = 1000
+
+// Path returns a tile coordinate path describing t.
+func (t Tile) Path() string {
+	n := t.N
+	nStr := fmt.Sprintf("%03d", n%pathBase)
+	for n >= pathBase {
+		n /= pathBase
+		nStr = fmt.Sprintf("x%03d/%s", n%pathBase, nStr)
+	}
+	pStr := ""
+	if t.W != 1<<uint(t.H) {
+		pStr = fmt.Sprintf(".p/%d", t.W)
+	}
+	var L string
+	if t.L == -1 {
+		L = "data"
+	} else {
+		L = fmt.Sprintf("%d", t.L)
+	}
+	return fmt.Sprintf("tile/%d/%s/%s%s", t.H, L, nStr, pStr)
+}
+
+// ParseTilePath parses a tile coordinate path.
+func ParseTilePath(path string) (Tile, error) {
+	f := strings.Split(path, "/")
+	if len(f) < 4 || f[0] != "tile" {
+		return Tile{}, &badPathError{path}
+	}
+	h, err1 := strconv.Atoi(f[1])
+	isData := false
+	if f[2] == "data" {
+		isData = true
+		f[2] = "0"
+	}
+	l, err2 := strconv.Atoi(f[2])
+	if err1 != nil || err2 != nil || h < 1 || l < 0 || h > 30 {
+		return Tile{}, &badPathError{path}
+	}
+	w := 1 << uint(h)
+	if dotP := f[len(f)-2]; strings.HasSuffix(dotP, ".p") {
+		ww, err := strconv.Atoi(f[len(f)-1])
+		if err != nil || ww <= 0 || ww >= w {
+			return Tile{}, &badPathError{path}
+		}
+		w = ww
+		f[len(f)-2] = dotP[:len(dotP)-len(".p")]
+		f = f[:len(f)-1]
+	}
+	f = f[3:]
+	n := int64(0)
+	for _, s := range f {
+		nn, err := strconv.Atoi(strings.TrimPrefix(s, "x"))
+		if err != nil || nn < 0 || nn >= pathBase {
+			return Tile{}, &badPathError{path}
+		}
+		n = n*pathBase + int64(nn)
+	}
+	if isData {
+		l = -1
+	}
+	t := Tile{H: h, L: l, N: n, W: w}
+	if path != t.Path() {
+		return Tile{}, &badPathError{path}
+	}
+	return t, nil
+}
+
+type badPathError struct {
+	path string
+}
+
+func (e *badPathError) Error() string {
+	return fmt.Sprintf("malformed tile path %q", e.path)
+}
+
+// A TileReader reads tiles from a go.sum database log.
+type TileReader interface {
+	// Height returns the height of the available tiles.
+	Height() int
+
+	// ReadTiles returns the data for each requested tile.
+	// If ReadTiles returns err == nil, it must also return
+	// a data record for each tile (len(data) == len(tiles))
+	// and each data record must be the correct length
+	// (len(data[i]) == tiles[i].W*HashSize).
+	//
+	// An implementation of ReadTiles typically reads
+	// them from an on-disk cache or else from a remote
+	// tile server. Tile data downloaded from a server should
+	// be considered suspect and not saved into a persistent
+	// on-disk cache before returning from ReadTiles.
+	// When the client confirms the validity of the tile data,
+	// it will call SaveTiles to signal that they can be safely
+	// written to persistent storage.
+	// See also https://research.swtch.com/tlog#authenticating_tiles.
+	ReadTiles(tiles []Tile) (data [][]byte, err error)
+
+	// SaveTiles informs the TileReader that the tile data
+	// returned by ReadTiles has been confirmed as valid
+	// and can be saved in persistent storage (on disk).
+	SaveTiles(tiles []Tile, data [][]byte)
+}
+
+// TileHashReader returns a HashReader that satisfies requests
+// by loading tiles of the given tree.
+//
+// The returned [HashReader] checks that loaded tiles are
+// valid for the given tree. Therefore, any hashes returned
+// by the HashReader are already proven to be in the tree.
+func TileHashReader(tree Tree, tr TileReader) HashReader {
+	return &tileHashReader{tree: tree, tr: tr}
+}
+
+type tileHashReader struct {
+	tree Tree
+	tr   TileReader
+}
+
+// tileParent returns t's k'th tile parent in the tiles for a tree of size n.
+// If there is no such parent, tileParent returns Tile{}.
+func tileParent(t Tile, k int, n int64) Tile {
+	t.L += k
+	t.N >>= uint(k * t.H)
+	t.W = 1 << uint(t.H)
+	if max := n >> uint(t.L*t.H); t.N<<uint(t.H)+int64(t.W) >= max {
+		if t.N<<uint(t.H) >= max {
+			return Tile{}
+		}
+		t.W = int(max - t.N<<uint(t.H))
+	}
+	return t
+}
+
+func (r *tileHashReader) ReadHashes(indexes []int64) ([]Hash, error) {
+	h := r.tr.Height()
+
+	tileOrder := make(map[Tile]int) // tileOrder[tileKey(tiles[i])] = i
+	var tiles []Tile
+
+	// Plan to fetch tiles necessary to recompute tree hash.
+	// If it matches, those tiles are authenticated.
+	stx := subTreeIndex(0, r.tree.N, nil)
+	stxTileOrder := make([]int, len(stx))
+	for i, x := range stx {
+		tile, _, _ := tileForIndex(h, x)
+		tile = tileParent(tile, 0, r.tree.N)
+		if j, ok := tileOrder[tile]; ok {
+			stxTileOrder[i] = j
+			continue
+		}
+		stxTileOrder[i] = len(tiles)
+		tileOrder[tile] = len(tiles)
+		tiles = append(tiles, tile)
+	}
+
+	// Plan to fetch tiles containing the indexes,
+	// along with any parent tiles needed
+	// for authentication. For most calls,
+	// the parents are being fetched anyway.
+	indexTileOrder := make([]int, len(indexes))
+	for i, x := range indexes {
+		if x >= StoredHashIndex(0, r.tree.N) {
+			return nil, fmt.Errorf("indexes not in tree")
+		}
+
+		tile, _, _ := tileForIndex(h, x)
+
+		// Walk up parent tiles until we find one we've requested.
+		// That one will be authenticated.
+		k := 0
+		for ; ; k++ {
+			p := tileParent(tile, k, r.tree.N)
+			if j, ok := tileOrder[p]; ok {
+				if k == 0 {
+					indexTileOrder[i] = j
+				}
+				break
+			}
+		}
+
+		// Walk back down recording child tiles after parents.
+		// This loop ends by revisiting the tile for this index
+		// (tileParent(tile, 0, r.tree.N)) unless k == 0, in which
+		// case the previous loop did it.
+		for k--; k >= 0; k-- {
+			p := tileParent(tile, k, r.tree.N)
+			if p.W != 1<<uint(p.H) {
+				// Only full tiles have parents.
+				// This tile has a parent, so it must be full.
+				return nil, fmt.Errorf("bad math in tileHashReader: %d %d %v", r.tree.N, x, p)
+			}
+			tileOrder[p] = len(tiles)
+			if k == 0 {
+				indexTileOrder[i] = len(tiles)
+			}
+			tiles = append(tiles, p)
+		}
+	}
+
+	// Fetch all the tile data.
+	data, err := r.tr.ReadTiles(tiles)
+	if err != nil {
+		return nil, err
+	}
+	if len(data) != len(tiles) {
+		return nil, fmt.Errorf("TileReader returned bad result slice (len=%d, want %d)", len(data), len(tiles))
+	}
+	for i, tile := range tiles {
+		if len(data[i]) != tile.W*HashSize {
+			return nil, fmt.Errorf("TileReader returned bad result slice (%v len=%d, want %d)", tile.Path(), len(data[i]), tile.W*HashSize)
+		}
+	}
+
+	// Authenticate the initial tiles against the tree hash.
+	// They are arranged so that parents are authenticated before children.
+	// First the tiles needed for the tree hash.
+	th, err := HashFromTile(tiles[stxTileOrder[len(stx)-1]], data[stxTileOrder[len(stx)-1]], stx[len(stx)-1])
+	if err != nil {
+		return nil, err
+	}
+	for i := len(stx) - 2; i >= 0; i-- {
+		h, err := HashFromTile(tiles[stxTileOrder[i]], data[stxTileOrder[i]], stx[i])
+		if err != nil {
+			return nil, err
+		}
+		th = NodeHash(h, th)
+	}
+	if th != r.tree.Hash {
+		// The tiles do not support the tree hash.
+		// We know at least one is wrong, but not which one.
+		return nil, fmt.Errorf("downloaded inconsistent tile")
+	}
+
+	// Authenticate full tiles against their parents.
+	for i := len(stx); i < len(tiles); i++ {
+		tile := tiles[i]
+		p := tileParent(tile, 1, r.tree.N)
+		j, ok := tileOrder[p]
+		if !ok {
+			return nil, fmt.Errorf("bad math in tileHashReader %d %v: lost parent of %v", r.tree.N, indexes, tile)
+		}
+		h, err := HashFromTile(p, data[j], StoredHashIndex(p.L*p.H, tile.N))
+		if err != nil {
+			return nil, fmt.Errorf("bad math in tileHashReader %d %v: lost hash of %v: %v", r.tree.N, indexes, tile, err)
+		}
+		if h != tileHash(data[i]) {
+			return nil, fmt.Errorf("downloaded inconsistent tile")
+		}
+	}
+
+	// Now we have all the tiles needed for the requested hashes,
+	// and we've authenticated the full tile set against the trusted tree hash.
+	r.tr.SaveTiles(tiles, data)
+
+	// Pull out the requested hashes.
+	hashes := make([]Hash, len(indexes))
+	for i, x := range indexes {
+		j := indexTileOrder[i]
+		h, err := HashFromTile(tiles[j], data[j], x)
+		if err != nil {
+			return nil, fmt.Errorf("bad math in tileHashReader %d %v: lost hash %v: %v", r.tree.N, indexes, x, err)
+		}
+		hashes[i] = h
+	}
+
+	return hashes, nil
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/tile_test.go

@@ -0,0 +1,24 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tlog
+
+import (
+	"testing"
+)
+
+// FuzzParseTilePath tests that ParseTilePath never crashes
+func FuzzParseTilePath(f *testing.F) {
+	f.Add("tile/4/0/001")
+	f.Add("tile/4/0/001.p/5")
+	f.Add("tile/3/5/x123/x456/078")
+	f.Add("tile/3/5/x123/x456/078.p/2")
+	f.Add("tile/1/0/x003/x057/500")
+	f.Add("tile/3/5/123/456/078")
+	f.Add("tile/3/-1/123/456/078")
+	f.Add("tile/1/data/x003/x057/500")
+	f.Fuzz(func(t *testing.T, path string) {
+		ParseTilePath(path)
+	})
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/tlog.go

@@ -0,0 +1,597 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tlog implements a tamper-evident log
+// used in the Go module go.sum database server.
+//
+// This package follows the design of Certificate Transparency (RFC 6962)
+// and its proofs are compatible with that system.
+// See TestCertificateTransparency.
+package tlog
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"math/bits"
+)
+
+// A Hash is a hash identifying a log record or tree root.
+type Hash [HashSize]byte
+
+// HashSize is the size of a Hash in bytes.
+const HashSize = 32
+
+// String returns a base64 representation of the hash for printing.
+func (h Hash) String() string {
+	return base64.StdEncoding.EncodeToString(h[:])
+}
+
+// MarshalJSON marshals the hash as a JSON string containing the base64-encoded hash.
+func (h Hash) MarshalJSON() ([]byte, error) {
+	return []byte(`"` + h.String() + `"`), nil
+}
+
+// UnmarshalJSON unmarshals a hash from JSON string containing the a base64-encoded hash.
+func (h *Hash) UnmarshalJSON(data []byte) error {
+	if len(data) != 1+44+1 || data[0] != '"' || data[len(data)-2] != '=' || data[len(data)-1] != '"' {
+		return errors.New("cannot decode hash")
+	}
+
+	// As of Go 1.12, base64.StdEncoding.Decode insists on
+	// slicing into target[33:] even when it only writes 32 bytes.
+	// Since we already checked that the hash ends in = above,
+	// we can use base64.RawStdEncoding with the = removed;
+	// RawStdEncoding does not exhibit the same bug.
+	// We decode into a temporary to avoid writing anything to *h
+	// unless the entire input is well-formed.
+	var tmp Hash
+	n, err := base64.RawStdEncoding.Decode(tmp[:], data[1:len(data)-2])
+	if err != nil || n != HashSize {
+		return errors.New("cannot decode hash")
+	}
+	*h = tmp
+	return nil
+}
+
+// ParseHash parses the base64-encoded string form of a hash.
+func ParseHash(s string) (Hash, error) {
+	data, err := base64.StdEncoding.DecodeString(s)
+	if err != nil || len(data) != HashSize {
+		return Hash{}, fmt.Errorf("malformed hash")
+	}
+	var h Hash
+	copy(h[:], data)
+	return h, nil
+}
+
+// maxpow2 returns k, the maximum power of 2 smaller than n,
+// as well as l = log₂ k (so k = 1<<l).
+func maxpow2(n int64) (k int64, l int) {
+	l = 0
+	for 1<<uint(l+1) < n {
+		l++
+	}
+	return 1 << uint(l), l
+}
+
+var zeroPrefix = []byte{0x00}
+
+// RecordHash returns the content hash for the given record data.
+func RecordHash(data []byte) Hash {
+	// SHA256(0x00 || data)
+	// https://tools.ietf.org/html/rfc6962#section-2.1
+	h := sha256.New()
+	h.Write(zeroPrefix)
+	h.Write(data)
+	var h1 Hash
+	h.Sum(h1[:0])
+	return h1
+}
+
+// NodeHash returns the hash for an interior tree node with the given left and right hashes.
+func NodeHash(left, right Hash) Hash {
+	// SHA256(0x01 || left || right)
+	// https://tools.ietf.org/html/rfc6962#section-2.1
+	// We use a stack buffer to assemble the hash input
+	// to avoid allocating a hash struct with sha256.New.
+	var buf [1 + HashSize + HashSize]byte
+	buf[0] = 0x01
+	copy(buf[1:], left[:])
+	copy(buf[1+HashSize:], right[:])
+	return sha256.Sum256(buf[:])
+}
+
+// For information about the stored hash index ordering,
+// see section 3.3 of Crosby and Wallach's paper
+// "Efficient Data Structures for Tamper-Evident Logging".
+// https://www.usenix.org/legacy/event/sec09/tech/full_papers/crosby.pdf
+
+// StoredHashIndex maps the tree coordinates (level, n)
+// to a dense linear ordering that can be used for hash storage.
+// Hash storage implementations that store hashes in sequential
+// storage can use this function to compute where to read or write
+// a given hash.
+func StoredHashIndex(level int, n int64) int64 {
+	// Level L's n'th hash is written right after level L+1's 2n+1'th hash.
+	// Work our way down to the level 0 ordering.
+	// We'll add back the original level count at the end.
+	for l := level; l > 0; l-- {
+		n = 2*n + 1
+	}
+
+	// Level 0's n'th hash is written at n+n/2+n/4+... (eventually n/2ⁱ hits zero).
+	i := int64(0)
+	for ; n > 0; n >>= 1 {
+		i += n
+	}
+
+	return i + int64(level)
+}
+
+// SplitStoredHashIndex is the inverse of [StoredHashIndex].
+// That is, SplitStoredHashIndex(StoredHashIndex(level, n)) == level, n.
+func SplitStoredHashIndex(index int64) (level int, n int64) {
+	// Determine level 0 record before index.
+	// StoredHashIndex(0, n) < 2*n,
+	// so the n we want is in [index/2, index/2+log₂(index)].
+	n = index / 2
+	indexN := StoredHashIndex(0, n)
+	if indexN > index {
+		panic("bad math")
+	}
+	for {
+		// Each new record n adds 1 + trailingZeros(n) hashes.
+		x := indexN + 1 + int64(bits.TrailingZeros64(uint64(n+1)))
+		if x > index {
+			break
+		}
+		n++
+		indexN = x
+	}
+	// The hash we want was committed with record n,
+	// meaning it is one of (0, n), (1, n/2), (2, n/4), ...
+	level = int(index - indexN)
+	return level, n >> uint(level)
+}
+
+// StoredHashCount returns the number of stored hashes
+// that are expected for a tree with n records.
+func StoredHashCount(n int64) int64 {
+	if n == 0 {
+		return 0
+	}
+	// The tree will have the hashes up to the last leaf hash.
+	numHash := StoredHashIndex(0, n-1) + 1
+	// And it will have any hashes for subtrees completed by that leaf.
+	for i := uint64(n - 1); i&1 != 0; i >>= 1 {
+		numHash++
+	}
+	return numHash
+}
+
+// StoredHashes returns the hashes that must be stored when writing
+// record n with the given data. The hashes should be stored starting
+// at StoredHashIndex(0, n). The result will have at most 1 + log₂ n hashes,
+// but it will average just under two per call for a sequence of calls for n=1..k.
+//
+// StoredHashes may read up to log n earlier hashes from r
+// in order to compute hashes for completed subtrees.
+func StoredHashes(n int64, data []byte, r HashReader) ([]Hash, error) {
+	return StoredHashesForRecordHash(n, RecordHash(data), r)
+}
+
+// StoredHashesForRecordHash is like [StoredHashes] but takes
+// as its second argument RecordHash(data) instead of data itself.
+func StoredHashesForRecordHash(n int64, h Hash, r HashReader) ([]Hash, error) {
+	// Start with the record hash.
+	hashes := []Hash{h}
+
+	// Build list of indexes needed for hashes for completed subtrees.
+	// Each trailing 1 bit in the binary representation of n completes a subtree
+	// and consumes a hash from an adjacent subtree.
+	m := int(bits.TrailingZeros64(uint64(n + 1)))
+	indexes := make([]int64, m)
+	for i := 0; i < m; i++ {
+		// We arrange indexes in sorted order.
+		// Note that n>>i is always odd.
+		indexes[m-1-i] = StoredHashIndex(i, n>>uint(i)-1)
+	}
+
+	// Fetch hashes.
+	old, err := r.ReadHashes(indexes)
+	if err != nil {
+		return nil, err
+	}
+	if len(old) != len(indexes) {
+		return nil, fmt.Errorf("tlog: ReadHashes(%d indexes) = %d hashes", len(indexes), len(old))
+	}
+
+	// Build new hashes.
+	for i := 0; i < m; i++ {
+		h = NodeHash(old[m-1-i], h)
+		hashes = append(hashes, h)
+	}
+	return hashes, nil
+}
+
+// A HashReader can read hashes for nodes in the log's tree structure.
+type HashReader interface {
+	// ReadHashes returns the hashes with the given stored hash indexes
+	// (see StoredHashIndex and SplitStoredHashIndex).
+	// ReadHashes must return a slice of hashes the same length as indexes,
+	// or else it must return a non-nil error.
+	// ReadHashes may run faster if indexes is sorted in increasing order.
+	ReadHashes(indexes []int64) ([]Hash, error)
+}
+
+// A HashReaderFunc is a function implementing [HashReader].
+type HashReaderFunc func([]int64) ([]Hash, error)
+
+func (f HashReaderFunc) ReadHashes(indexes []int64) ([]Hash, error) {
+	return f(indexes)
+}
+
+// TreeHash computes the hash for the root of the tree with n records,
+// using the HashReader to obtain previously stored hashes
+// (those returned by StoredHashes during the writes of those n records).
+// TreeHash makes a single call to ReadHash requesting at most 1 + log₂ n hashes.
+// The tree of size zero is defined to have an all-zero Hash.
+func TreeHash(n int64, r HashReader) (Hash, error) {
+	if n == 0 {
+		return Hash{}, nil
+	}
+	indexes := subTreeIndex(0, n, nil)
+	hashes, err := r.ReadHashes(indexes)
+	if err != nil {
+		return Hash{}, err
+	}
+	if len(hashes) != len(indexes) {
+		return Hash{}, fmt.Errorf("tlog: ReadHashes(%d indexes) = %d hashes", len(indexes), len(hashes))
+	}
+	hash, hashes := subTreeHash(0, n, hashes)
+	if len(hashes) != 0 {
+		panic("tlog: bad index math in TreeHash")
+	}
+	return hash, nil
+}
+
+// subTreeIndex returns the storage indexes needed to compute
+// the hash for the subtree containing records [lo, hi),
+// appending them to need and returning the result.
+// See https://tools.ietf.org/html/rfc6962#section-2.1
+func subTreeIndex(lo, hi int64, need []int64) []int64 {
+	// See subTreeHash below for commentary.
+	for lo < hi {
+		k, level := maxpow2(hi - lo + 1)
+		if lo&(k-1) != 0 {
+			panic("tlog: bad math in subTreeIndex")
+		}
+		need = append(need, StoredHashIndex(level, lo>>uint(level)))
+		lo += k
+	}
+	return need
+}
+
+// subTreeHash computes the hash for the subtree containing records [lo, hi),
+// assuming that hashes are the hashes corresponding to the indexes
+// returned by subTreeIndex(lo, hi).
+// It returns any leftover hashes.
+func subTreeHash(lo, hi int64, hashes []Hash) (Hash, []Hash) {
+	// Repeatedly partition the tree into a left side with 2^level nodes,
+	// for as large a level as possible, and a right side with the fringe.
+	// The left hash is stored directly and can be read from storage.
+	// The right side needs further computation.
+	numTree := 0
+	for lo < hi {
+		k, _ := maxpow2(hi - lo + 1)
+		if lo&(k-1) != 0 || lo >= hi {
+			panic("tlog: bad math in subTreeHash")
+		}
+		numTree++
+		lo += k
+	}
+
+	if len(hashes) < numTree {
+		panic("tlog: bad index math in subTreeHash")
+	}
+
+	// Reconstruct hash.
+	h := hashes[numTree-1]
+	for i := numTree - 2; i >= 0; i-- {
+		h = NodeHash(hashes[i], h)
+	}
+	return h, hashes[numTree:]
+}
+
+// A RecordProof is a verifiable proof that a particular log root contains a particular record.
+// RFC 6962 calls this a “Merkle audit path.”
+type RecordProof []Hash
+
+// ProveRecord returns the proof that the tree of size t contains the record with index n.
+func ProveRecord(t, n int64, r HashReader) (RecordProof, error) {
+	if t < 0 || n < 0 || n >= t {
+		return nil, fmt.Errorf("tlog: invalid inputs in ProveRecord")
+	}
+	indexes := leafProofIndex(0, t, n, nil)
+	if len(indexes) == 0 {
+		return RecordProof{}, nil
+	}
+	hashes, err := r.ReadHashes(indexes)
+	if err != nil {
+		return nil, err
+	}
+	if len(hashes) != len(indexes) {
+		return nil, fmt.Errorf("tlog: ReadHashes(%d indexes) = %d hashes", len(indexes), len(hashes))
+	}
+
+	p, hashes := leafProof(0, t, n, hashes)
+	if len(hashes) != 0 {
+		panic("tlog: bad index math in ProveRecord")
+	}
+	return p, nil
+}
+
+// leafProofIndex builds the list of indexes needed to construct the proof
+// that leaf n is contained in the subtree with leaves [lo, hi).
+// It appends those indexes to need and returns the result.
+// See https://tools.ietf.org/html/rfc6962#section-2.1.1
+func leafProofIndex(lo, hi, n int64, need []int64) []int64 {
+	// See leafProof below for commentary.
+	if !(lo <= n && n < hi) {
+		panic("tlog: bad math in leafProofIndex")
+	}
+	if lo+1 == hi {
+		return need
+	}
+	if k, _ := maxpow2(hi - lo); n < lo+k {
+		need = leafProofIndex(lo, lo+k, n, need)
+		need = subTreeIndex(lo+k, hi, need)
+	} else {
+		need = subTreeIndex(lo, lo+k, need)
+		need = leafProofIndex(lo+k, hi, n, need)
+	}
+	return need
+}
+
+// leafProof constructs the proof that leaf n is contained in the subtree with leaves [lo, hi).
+// It returns any leftover hashes as well.
+// See https://tools.ietf.org/html/rfc6962#section-2.1.1
+func leafProof(lo, hi, n int64, hashes []Hash) (RecordProof, []Hash) {
+	// We must have lo <= n < hi or else the code here has a bug.
+	if !(lo <= n && n < hi) {
+		panic("tlog: bad math in leafProof")
+	}
+
+	if lo+1 == hi { // n == lo
+		// Reached the leaf node.
+		// The verifier knows what the leaf hash is, so we don't need to send it.
+		return RecordProof{}, hashes
+	}
+
+	// Walk down the tree toward n.
+	// Record the hash of the path not taken (needed for verifying the proof).
+	var p RecordProof
+	var th Hash
+	if k, _ := maxpow2(hi - lo); n < lo+k {
+		// n is on left side
+		p, hashes = leafProof(lo, lo+k, n, hashes)
+		th, hashes = subTreeHash(lo+k, hi, hashes)
+	} else {
+		// n is on right side
+		th, hashes = subTreeHash(lo, lo+k, hashes)
+		p, hashes = leafProof(lo+k, hi, n, hashes)
+	}
+	return append(p, th), hashes
+}
+
+var errProofFailed = errors.New("invalid transparency proof")
+
+// CheckRecord verifies that p is a valid proof that the tree of size t
+// with hash th has an n'th record with hash h.
+func CheckRecord(p RecordProof, t int64, th Hash, n int64, h Hash) error {
+	if t < 0 || n < 0 || n >= t {
+		return fmt.Errorf("tlog: invalid inputs in CheckRecord")
+	}
+	th2, err := runRecordProof(p, 0, t, n, h)
+	if err != nil {
+		return err
+	}
+	if th2 == th {
+		return nil
+	}
+	return errProofFailed
+}
+
+// runRecordProof runs the proof p that leaf n is contained in the subtree with leaves [lo, hi).
+// Running the proof means constructing and returning the implied hash of that
+// subtree.
+func runRecordProof(p RecordProof, lo, hi, n int64, leafHash Hash) (Hash, error) {
+	// We must have lo <= n < hi or else the code here has a bug.
+	if !(lo <= n && n < hi) {
+		panic("tlog: bad math in runRecordProof")
+	}
+
+	if lo+1 == hi { // m == lo
+		// Reached the leaf node.
+		// The proof must not have any unnecessary hashes.
+		if len(p) != 0 {
+			return Hash{}, errProofFailed
+		}
+		return leafHash, nil
+	}
+
+	if len(p) == 0 {
+		return Hash{}, errProofFailed
+	}
+
+	k, _ := maxpow2(hi - lo)
+	if n < lo+k {
+		th, err := runRecordProof(p[:len(p)-1], lo, lo+k, n, leafHash)
+		if err != nil {
+			return Hash{}, err
+		}
+		return NodeHash(th, p[len(p)-1]), nil
+	} else {
+		th, err := runRecordProof(p[:len(p)-1], lo+k, hi, n, leafHash)
+		if err != nil {
+			return Hash{}, err
+		}
+		return NodeHash(p[len(p)-1], th), nil
+	}
+}
+
+// A TreeProof is a verifiable proof that a particular log tree contains
+// as a prefix all records present in an earlier tree.
+// RFC 6962 calls this a “Merkle consistency proof.”
+type TreeProof []Hash
+
+// ProveTree returns the proof that the tree of size t contains
+// as a prefix all the records from the tree of smaller size n.
+func ProveTree(t, n int64, h HashReader) (TreeProof, error) {
+	if t < 1 || n < 1 || n > t {
+		return nil, fmt.Errorf("tlog: invalid inputs in ProveTree")
+	}
+	indexes := treeProofIndex(0, t, n, nil)
+	if len(indexes) == 0 {
+		return TreeProof{}, nil
+	}
+	hashes, err := h.ReadHashes(indexes)
+	if err != nil {
+		return nil, err
+	}
+	if len(hashes) != len(indexes) {
+		return nil, fmt.Errorf("tlog: ReadHashes(%d indexes) = %d hashes", len(indexes), len(hashes))
+	}
+
+	p, hashes := treeProof(0, t, n, hashes)
+	if len(hashes) != 0 {
+		panic("tlog: bad index math in ProveTree")
+	}
+	return p, nil
+}
+
+// treeProofIndex builds the list of indexes needed to construct
+// the sub-proof related to the subtree containing records [lo, hi).
+// See https://tools.ietf.org/html/rfc6962#section-2.1.2.
+func treeProofIndex(lo, hi, n int64, need []int64) []int64 {
+	// See treeProof below for commentary.
+	if !(lo < n && n <= hi) {
+		panic("tlog: bad math in treeProofIndex")
+	}
+
+	if n == hi {
+		if lo == 0 {
+			return need
+		}
+		return subTreeIndex(lo, hi, need)
+	}
+
+	if k, _ := maxpow2(hi - lo); n <= lo+k {
+		need = treeProofIndex(lo, lo+k, n, need)
+		need = subTreeIndex(lo+k, hi, need)
+	} else {
+		need = subTreeIndex(lo, lo+k, need)
+		need = treeProofIndex(lo+k, hi, n, need)
+	}
+	return need
+}
+
+// treeProof constructs the sub-proof related to the subtree containing records [lo, hi).
+// It returns any leftover hashes as well.
+// See https://tools.ietf.org/html/rfc6962#section-2.1.2.
+func treeProof(lo, hi, n int64, hashes []Hash) (TreeProof, []Hash) {
+	// We must have lo < n <= hi or else the code here has a bug.
+	if !(lo < n && n <= hi) {
+		panic("tlog: bad math in treeProof")
+	}
+
+	// Reached common ground.
+	if n == hi {
+		if lo == 0 {
+			// This subtree corresponds exactly to the old tree.
+			// The verifier knows that hash, so we don't need to send it.
+			return TreeProof{}, hashes
+		}
+		th, hashes := subTreeHash(lo, hi, hashes)
+		return TreeProof{th}, hashes
+	}
+
+	// Interior node for the proof.
+	// Decide whether to walk down the left or right side.
+	var p TreeProof
+	var th Hash
+	if k, _ := maxpow2(hi - lo); n <= lo+k {
+		// m is on left side
+		p, hashes = treeProof(lo, lo+k, n, hashes)
+		th, hashes = subTreeHash(lo+k, hi, hashes)
+	} else {
+		// m is on right side
+		th, hashes = subTreeHash(lo, lo+k, hashes)
+		p, hashes = treeProof(lo+k, hi, n, hashes)
+	}
+	return append(p, th), hashes
+}
+
+// CheckTree verifies that p is a valid proof that the tree of size t with hash th
+// contains as a prefix the tree of size n with hash h.
+func CheckTree(p TreeProof, t int64, th Hash, n int64, h Hash) error {
+	if t < 1 || n < 1 || n > t {
+		return fmt.Errorf("tlog: invalid inputs in CheckTree")
+	}
+	h2, th2, err := runTreeProof(p, 0, t, n, h)
+	if err != nil {
+		return err
+	}
+	if th2 == th && h2 == h {
+		return nil
+	}
+	return errProofFailed
+}
+
+// runTreeProof runs the sub-proof p related to the subtree containing records [lo, hi),
+// where old is the hash of the old tree with n records.
+// Running the proof means constructing and returning the implied hashes of that
+// subtree in both the old and new tree.
+func runTreeProof(p TreeProof, lo, hi, n int64, old Hash) (Hash, Hash, error) {
+	// We must have lo < n <= hi or else the code here has a bug.
+	if !(lo < n && n <= hi) {
+		panic("tlog: bad math in runTreeProof")
+	}
+
+	// Reached common ground.
+	if n == hi {
+		if lo == 0 {
+			if len(p) != 0 {
+				return Hash{}, Hash{}, errProofFailed
+			}
+			return old, old, nil
+		}
+		if len(p) != 1 {
+			return Hash{}, Hash{}, errProofFailed
+		}
+		return p[0], p[0], nil
+	}
+
+	if len(p) == 0 {
+		return Hash{}, Hash{}, errProofFailed
+	}
+
+	// Interior node for the proof.
+	k, _ := maxpow2(hi - lo)
+	if n <= lo+k {
+		oh, th, err := runTreeProof(p[:len(p)-1], lo, lo+k, n, old)
+		if err != nil {
+			return Hash{}, Hash{}, err
+		}
+		return oh, NodeHash(th, p[len(p)-1]), nil
+	} else {
+		oh, th, err := runTreeProof(p[:len(p)-1], lo+k, hi, n, old)
+		if err != nil {
+			return Hash{}, Hash{}, err
+		}
+		return NodeHash(p[len(p)-1], oh), NodeHash(p[len(p)-1], th), nil
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/sumdb/tlog/tlog_test.go

@@ -0,0 +1,269 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tlog
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+type testHashStorage []Hash
+
+func (t testHashStorage) ReadHash(level int, n int64) (Hash, error) {
+	return t[StoredHashIndex(level, n)], nil
+}
+
+func (t testHashStorage) ReadHashes(index []int64) ([]Hash, error) {
+	// It's not required by HashReader that indexes be in increasing order,
+	// but check that the functions we are testing only ever ask for
+	// indexes in increasing order.
+	for i := 1; i < len(index); i++ {
+		if index[i-1] >= index[i] {
+			panic("indexes out of order")
+		}
+	}
+
+	out := make([]Hash, len(index))
+	for i, x := range index {
+		out[i] = t[x]
+	}
+	return out, nil
+}
+
+type testTilesStorage struct {
+	unsaved int
+	m       map[Tile][]byte
+}
+
+func (t testTilesStorage) Height() int {
+	return 2
+}
+
+func (t *testTilesStorage) SaveTiles(tiles []Tile, data [][]byte) {
+	t.unsaved -= len(tiles)
+}
+
+func (t *testTilesStorage) ReadTiles(tiles []Tile) ([][]byte, error) {
+	out := make([][]byte, len(tiles))
+	for i, tile := range tiles {
+		out[i] = t.m[tile]
+	}
+	t.unsaved += len(tiles)
+	return out, nil
+}
+
+func TestTree(t *testing.T) {
+	var trees []Hash
+	var leafhashes []Hash
+	var storage testHashStorage
+	tiles := make(map[Tile][]byte)
+	const testH = 2
+	for i := int64(0); i < 100; i++ {
+		data := []byte(fmt.Sprintf("leaf %d", i))
+		hashes, err := StoredHashes(i, data, storage)
+		if err != nil {
+			t.Fatal(err)
+		}
+		leafhashes = append(leafhashes, RecordHash(data))
+		oldStorage := len(storage)
+		storage = append(storage, hashes...)
+		if count := StoredHashCount(i + 1); count != int64(len(storage)) {
+			t.Errorf("StoredHashCount(%d) = %d, have %d StoredHashes", i+1, count, len(storage))
+		}
+		th, err := TreeHash(i+1, storage)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for _, tile := range NewTiles(testH, i, i+1) {
+			data, err := ReadTileData(tile, storage)
+			if err != nil {
+				t.Fatal(err)
+			}
+			old := Tile{H: tile.H, L: tile.L, N: tile.N, W: tile.W - 1}
+			oldData := tiles[old]
+			if len(oldData) != len(data)-HashSize || !bytes.Equal(oldData, data[:len(oldData)]) {
+				t.Fatalf("tile %v not extending earlier tile %v", tile.Path(), old.Path())
+			}
+			tiles[tile] = data
+		}
+		for _, tile := range NewTiles(testH, 0, i+1) {
+			data, err := ReadTileData(tile, storage)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !bytes.Equal(tiles[tile], data) {
+				t.Fatalf("mismatch at %+v", tile)
+			}
+		}
+		for _, tile := range NewTiles(testH, i/2, i+1) {
+			data, err := ReadTileData(tile, storage)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !bytes.Equal(tiles[tile], data) {
+				t.Fatalf("mismatch at %+v", tile)
+			}
+		}
+
+		// Check that all the new hashes are readable from their tiles.
+		for j := oldStorage; j < len(storage); j++ {
+			tile := TileForIndex(testH, int64(j))
+			data, ok := tiles[tile]
+			if !ok {
+				t.Log(NewTiles(testH, 0, i+1))
+				t.Fatalf("TileForIndex(%d, %d) = %v, not yet stored (i=%d, stored %d)", testH, j, tile.Path(), i, len(storage))
+				continue
+			}
+			h, err := HashFromTile(tile, data, int64(j))
+			if err != nil {
+				t.Fatal(err)
+			}
+			if h != storage[j] {
+				t.Errorf("HashFromTile(%v, %d) = %v, want %v", tile.Path(), int64(j), h, storage[j])
+			}
+		}
+
+		trees = append(trees, th)
+
+		// Check that leaf proofs work, for all trees and leaves so far.
+		for j := int64(0); j <= i; j++ {
+			p, err := ProveRecord(i+1, j, storage)
+			if err != nil {
+				t.Fatalf("ProveRecord(%d, %d): %v", i+1, j, err)
+			}
+			if err := CheckRecord(p, i+1, th, j, leafhashes[j]); err != nil {
+				t.Fatalf("CheckRecord(%d, %d): %v", i+1, j, err)
+			}
+			for k := range p {
+				p[k][0] ^= 1
+				if err := CheckRecord(p, i+1, th, j, leafhashes[j]); err == nil {
+					t.Fatalf("CheckRecord(%d, %d) succeeded with corrupt proof hash #%d!", i+1, j, k)
+				}
+				p[k][0] ^= 1
+			}
+		}
+
+		// Check that leaf proofs work using TileReader.
+		// To prove a leaf that way, all you have to do is read and verify its hash.
+		storage := &testTilesStorage{m: tiles}
+		thr := TileHashReader(Tree{i + 1, th}, storage)
+		for j := int64(0); j <= i; j++ {
+			h, err := thr.ReadHashes([]int64{StoredHashIndex(0, j)})
+			if err != nil {
+				t.Fatalf("TileHashReader(%d).ReadHashes(%d): %v", i+1, j, err)
+			}
+			if h[0] != leafhashes[j] {
+				t.Fatalf("TileHashReader(%d).ReadHashes(%d) returned wrong hash", i+1, j)
+			}
+
+			// Even though reading the hash suffices,
+			// check we can generate the proof too.
+			p, err := ProveRecord(i+1, j, thr)
+			if err != nil {
+				t.Fatalf("ProveRecord(%d, %d, TileHashReader(%d)): %v", i+1, j, i+1, err)
+			}
+			if err := CheckRecord(p, i+1, th, j, leafhashes[j]); err != nil {
+				t.Fatalf("CheckRecord(%d, %d, TileHashReader(%d)): %v", i+1, j, i+1, err)
+			}
+		}
+		if storage.unsaved != 0 {
+			t.Fatalf("TileHashReader(%d) did not save %d tiles", i+1, storage.unsaved)
+		}
+
+		// Check that ReadHashes will give an error if the index is not in the tree.
+		if _, err := thr.ReadHashes([]int64{(i + 1) * 2}); err == nil {
+			t.Fatalf("TileHashReader(%d).ReadHashes(%d) for index not in tree <nil>, want err", i, i+1)
+		}
+		if storage.unsaved != 0 {
+			t.Fatalf("TileHashReader(%d) did not save %d tiles", i+1, storage.unsaved)
+		}
+
+		// Check that tree proofs work, for all trees so far, using TileReader.
+		// To prove a tree that way, all you have to do is compute and verify its hash.
+		for j := int64(0); j <= i; j++ {
+			h, err := TreeHash(j+1, thr)
+			if err != nil {
+				t.Fatalf("TreeHash(%d, TileHashReader(%d)): %v", j, i+1, err)
+			}
+			if h != trees[j] {
+				t.Fatalf("TreeHash(%d, TileHashReader(%d)) = %x, want %x (%v)", j, i+1, h[:], trees[j][:], trees[j])
+			}
+
+			// Even though computing the subtree hash suffices,
+			// check that we can generate the proof too.
+			p, err := ProveTree(i+1, j+1, thr)
+			if err != nil {
+				t.Fatalf("ProveTree(%d, %d): %v", i+1, j+1, err)
+			}
+			if err := CheckTree(p, i+1, th, j+1, trees[j]); err != nil {
+				t.Fatalf("CheckTree(%d, %d): %v [%v]", i+1, j+1, err, p)
+			}
+			for k := range p {
+				p[k][0] ^= 1
+				if err := CheckTree(p, i+1, th, j+1, trees[j]); err == nil {
+					t.Fatalf("CheckTree(%d, %d) succeeded with corrupt proof hash #%d!", i+1, j+1, k)
+				}
+				p[k][0] ^= 1
+			}
+		}
+		if storage.unsaved != 0 {
+			t.Fatalf("TileHashReader(%d) did not save %d tiles", i+1, storage.unsaved)
+		}
+	}
+}
+
+func TestSplitStoredHashIndex(t *testing.T) {
+	for l := 0; l < 10; l++ {
+		for n := int64(0); n < 100; n++ {
+			x := StoredHashIndex(l, n)
+			l1, n1 := SplitStoredHashIndex(x)
+			if l1 != l || n1 != n {
+				t.Fatalf("StoredHashIndex(%d, %d) = %d, but SplitStoredHashIndex(%d) = %d, %d", l, n, x, x, l1, n1)
+			}
+		}
+	}
+}
+
+// TODO(rsc): Test invalid paths too, like "tile/3/5/123/456/078".
+var tilePaths = []struct {
+	path string
+	tile Tile
+}{
+	{"tile/4/0/001", Tile{4, 0, 1, 16}},
+	{"tile/4/0/001.p/5", Tile{4, 0, 1, 5}},
+	{"tile/3/5/x123/x456/078", Tile{3, 5, 123456078, 8}},
+	{"tile/3/5/x123/x456/078.p/2", Tile{3, 5, 123456078, 2}},
+	{"tile/1/0/x003/x057/500", Tile{1, 0, 3057500, 2}},
+	{"tile/3/5/123/456/078", Tile{}},
+	{"tile/3/-1/123/456/078", Tile{}},
+	{"tile/1/data/x003/x057/500", Tile{1, -1, 3057500, 2}},
+}
+
+func TestTilePath(t *testing.T) {
+	for _, tt := range tilePaths {
+		if tt.tile.H > 0 {
+			p := tt.tile.Path()
+			if p != tt.path {
+				t.Errorf("%+v.Path() = %q, want %q", tt.tile, p, tt.path)
+			}
+		}
+		tile, err := ParseTilePath(tt.path)
+		if err != nil {
+			if tt.tile.H == 0 {
+				// Expected error.
+				continue
+			}
+			t.Errorf("ParseTilePath(%q): %v", tt.path, err)
+		} else if tile != tt.tile {
+			if tt.tile.H == 0 {
+				t.Errorf("ParseTilePath(%q): expected error, got %+v", tt.path, tt.tile)
+				continue
+			}
+			t.Errorf("ParseTilePath(%q) = %+v, want %+v", tt.path, tile, tt.tile)
+		}
+	}
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/check_dir/empty.txt

@@ -0,0 +1,6 @@
+-- want --
+valid:
+
+omitted:
+
+invalid:

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/check_dir/various.txt

@@ -0,0 +1,20 @@
+-- want --
+valid:
+$work/valid.go
+
+omitted:
+$work/.hg_archival.txt: file is inserted by 'hg archive' and is always omitted
+$work/.git: directory is a version control repository
+$work/sub: directory is in another module
+$work/vendor/x/y: file is in vendor directory
+
+invalid:
+$work/GO.MOD: go.mod files must have lowercase names
+$work/invalid.go': malformed file path "invalid.go'": invalid char '\''
+-- valid.go --
+-- GO.MOD --
+-- invalid.go' --
+-- vendor/x/y --
+-- sub/go.mod --
+-- .hg_archival.txt --
+-- .git/x --

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/check_files/empty.txt

@@ -0,0 +1,6 @@
+-- want --
+valid:
+
+omitted:
+
+invalid:

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/check_files/various.txt

@@ -0,0 +1,25 @@
+-- want --
+valid:
+valid.go
+
+omitted:
+vendor/x/y: file is in vendor directory
+sub/go.mod: file is in another module
+.hg_archival.txt: file is inserted by 'hg archive' and is always omitted
+
+invalid:
+not/../clean: file path is not clean
+GO.MOD: go.mod files must have lowercase names
+invalid.go': malformed file path "invalid.go'": invalid char '\''
+valid.go: multiple entries for file "valid.go"
+-- valid.go --
+-- not/../clean --
+-- GO.MOD --
+-- invalid.go' --
+-- vendor/x/y --
+-- sub/go.mod --
+-- .hg_archival.txt --
+-- valid.go --
+duplicate
+-- valid.go --
+another duplicate

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/check_zip/empty.txt

@@ -0,0 +1,8 @@
+path=example.com/empty
+version=v1.0.0
+-- want --
+valid:
+
+omitted:
+
+invalid:

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/check_zip/various.txt

@@ -0,0 +1,21 @@
+path=example.com/various
+version=v1.0.0
+-- want --
+valid:
+example.com/various@v1.0.0/valid.go
+
+omitted:
+
+invalid:
+noprefix: path does not have prefix "example.com/various@v1.0.0/"
+example.com/various@v1.0.0/not/../clean: file path is not clean
+example.com/various@v1.0.0/invalid.go': malformed file path "invalid.go'": invalid char '\''
+example.com/various@v1.0.0/GO.MOD: go.mod files must have lowercase names
+example.com/various@v1.0.0/valid.go: multiple entries for file "valid.go"
+-- noprefix --
+-- example.com/various@v1.0.0/valid.go --
+-- example.com/various@v1.0.0/not/../clean --
+-- example.com/various@v1.0.0/invalid.go' --
+-- example.com/various@v1.0.0/GO.MOD --
+-- example.com/various@v1.0.0/valid.go --
+duplicate

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/bad_file_path.txt

@@ -0,0 +1,5 @@
+path=example.com/m
+version=v1.0.0
+wantErr=malformed file path "bad.go'": invalid char '\''
+-- bad.go' --
+package bad

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/bad_gomod_case.txt

@@ -0,0 +1,5 @@
+path=example.com/m
+version=v1.0.0
+wantErr=GO.MOD: go.mod files must have lowercase names
+-- GO.MOD --
+module example.com/m

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/bad_mod_path.txt

@@ -0,0 +1,3 @@
+path=cache
+version=v1.0.0
+wantErr=missing dot in first path element

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/bad_mod_path_version_suffix.txt

@@ -0,0 +1,3 @@
+path=example.com/m
+version=v2.0.0
+wantErr=invalid version: should be v0 or v1, not v2

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/bad_version.txt

@@ -0,0 +1,3 @@
+path=example.com/m
+version=v1.0.0+bad
+wantErr=version "v1.0.0+bad" is not canonical (should be "v1.0.0")

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/dup_file.txt

@@ -0,0 +1,7 @@
+path=example.com/m
+version=v1.0.0
+wantErr=multiple entries for file "dup.go"
+-- dup.go --
+package d1
+-- dup.go --
+package d2

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/dup_file_and_dir.txt

@@ -0,0 +1,7 @@
+path=example.com/m
+version=v1.0.0
+wantErr=entry "a.go" is both a file and a directory
+-- a.go --
+package a
+-- a.go/b.go --
+package b

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/empty.txt

@@ -0,0 +1,3 @@
+path=example.com/empty
+version=v1.0.0
+hash=h1:47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/exclude_cap_go_mod_submodule.txt

@@ -0,0 +1,9 @@
+path=example.com/m
+version=v1.0.0
+hash=h1:xctQQey8/y7IcBjFZDP/onWLSXhlqcsC3i1fgSdpMHk=
+-- a.go --
+package a
+-- b/GO.MOD --
+MODULE EXAMPLE.COM/M/B
+-- b/b.go --
+package b

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/exclude_submodule.txt

@@ -0,0 +1,11 @@
+path=example.com/m
+version=v1.0.0
+hash=h1:XduFAgX/GaspZa8Jv4pfzoGEzNaU/r88PiCunijw5ok=
+-- go.mod --
+module example.com/m
+
+go 1.13
+-- sub/go.mod --
+module example.com/m/sub
+-- sub/x.go' --
+invalid name, but this shouldn't be read

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/exclude_vendor.txt

@@ -0,0 +1,14 @@
+path=example.com/m
+version=v1.0.0
+hash=h1:5u93LDLN0Me+NGfZtRpA5mHxY8svfykHpq4CMSaBZyc=
+-- go.mod --
+module example.com/m
+
+go 1.13
+-- vendor/modules.txt --
+included
+see comment in isVendoredPackage and golang.org/issue/31562.
+-- vendor/example.com/x/x.go --
+excluded
+-- sub/vendor/sub.txt --
+excluded

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/file_case_conflict.txt

@@ -0,0 +1,7 @@
+path=example.com/m
+version=v1.0.0
+wantErr=case-insensitive file name collision: "m.go" and "M.GO"
+-- m.go --
+package m
+-- M.GO --
+package m

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/go_mod_dir.txt

@@ -0,0 +1,5 @@
+path=example.com/m
+version=v1.0.0
+hash=h1:Mun5l9cBlDnnV6JasTpio2aZJSbFj++h+814mnKC/OM=
+-- go.mod/a.go --
+package a

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/invalid_utf8_mod_path.txt

@@ -0,0 +1,3 @@
+path=ÿ  # 0xFF
+version=v1.0.0
+wantErr=malformed module path "\xff": invalid UTF-8

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create/simple.txt

@@ -0,0 +1,22 @@
+path=example.com/m
+version=v1.0.0
+hash=h1:tpqYOOmuilagXzyqoJ3roUjp8gneQeTv5YVpL6BG7/k=
+-- go.mod --
+module example.com/m
+
+go 1.13
+-- m.go --
+package m
+
+func Foo() int { return 42 }
+-- cmd/hello/hello.go --
+package main
+
+import (
+  "fmt"
+  "example.com/m"
+)
+
+func main() {
+  fmt.Println(m.Foo())
+}

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create_from_dir/bad_file_path.txt

@@ -0,0 +1,5 @@
+path=example.com/m
+version=v1.0.0
+wantErr=malformed file path "bad.go'": invalid char '\''
+-- bad.go' --
+package bad

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create_from_dir/bad_gomod_case.txt

@@ -0,0 +1,5 @@
+path=example.com/m
+version=v1.0.0
+wantErr=GO.MOD: go.mod files must have lowercase names
+-- GO.MOD --
+module example.com/m

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create_from_dir/bad_mod_path.txt

@@ -0,0 +1,3 @@
+path=cache
+version=v1.0.0
+wantErr=missing dot in first path element

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create_from_dir/bad_mod_path_version_suffix.txt

@@ -0,0 +1,3 @@
+path=example.com/m
+version=v2.0.0
+wantErr=invalid version: should be v0 or v1, not v2

go/pkg/mod/golang.org/x/mod@v0.14.0/zip/testdata/create_from_dir/bad_version.txt

@@ -0,0 +1,3 @@
+path=example.com/m
+version=v1.0.0+bad
+wantErr=version "v1.0.0+bad" is not canonical (should be "v1.0.0")