whatcanGOwrong

go/pkg/mod/golang.org/x/tools@v0.24.0/cmd/godoc/doc.go

@@ -0,0 +1,113 @@
+// Copyright 2009 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.
+
+/*
+Godoc extracts and generates documentation for Go programs.
+
+It runs as a web server and presents the documentation as a
+web page.
+
+	godoc -http=:6060
+
+Usage:
+
+	godoc [flag]
+
+The flags are:
+
+	-v
+		verbose mode
+	-timestamps=true
+		show timestamps with directory listings
+	-index
+		enable identifier and full text search index
+		(no search box is shown if -index is not set)
+	-index_files=""
+		glob pattern specifying index files; if not empty,
+		the index is read from these files in sorted order
+	-index_throttle=0.75
+		index throttle value; a value of 0 means no time is allocated
+		to the indexer (the indexer will never finish), a value of 1.0
+		means that index creation is running at full throttle (other
+		goroutines may get no time while the index is built)
+	-index_interval=0
+		interval of indexing; a value of 0 sets it to 5 minutes, a
+		negative value indexes only once at startup
+	-play=false
+		enable playground
+	-links=true
+		link identifiers to their declarations
+	-write_index=false
+		write index to a file; the file name must be specified with
+		-index_files
+	-maxresults=10000
+		maximum number of full text search results shown
+		(no full text index is built if maxresults <= 0)
+	-notes="BUG"
+		regular expression matching note markers to show
+		(e.g., "BUG|TODO", ".*")
+	-goroot=$GOROOT
+		Go root directory
+	-http=addr
+		HTTP service address (e.g., '127.0.0.1:6060' or just ':6060')
+	-templates=""
+		directory containing alternate template files; if set,
+		the directory may provide alternative template files
+		for the files in $GOROOT/lib/godoc
+	-url=path
+		print to standard output the data that would be served by
+		an HTTP request for path
+	-zip=""
+		zip file providing the file system to serve; disabled if empty
+
+By default, godoc looks at the packages it finds via $GOROOT and $GOPATH (if set).
+This behavior can be altered by providing an alternative $GOROOT with the -goroot
+flag.
+
+When the -index flag is set, a search index is maintained.
+The index is created at startup.
+
+The index contains both identifier and full text search information (searchable
+via regular expressions). The maximum number of full text search results shown
+can be set with the -maxresults flag; if set to 0, no full text results are
+shown, and only an identifier index but no full text search index is created.
+
+By default, godoc uses the system's GOOS/GOARCH. You can provide the URL parameters
+"GOOS" and "GOARCH" to set the output on the web page for the target system.
+
+The presentation mode of web pages served by godoc can be controlled with the
+"m" URL parameter; it accepts a comma-separated list of flag names as value:
+
+	all	show documentation for all declarations, not just the exported ones
+	methods	show all embedded methods, not just those of unexported anonymous fields
+	src	show the original source code rather than the extracted documentation
+	flat	present flat (not indented) directory listings using full paths
+
+For instance, https://golang.org/pkg/math/big/?m=all shows the documentation
+for all (not just the exported) declarations of package big.
+
+By default, godoc serves files from the file system of the underlying OS.
+Instead, a .zip file may be provided via the -zip flag, which contains
+the file system to serve. The file paths stored in the .zip file must use
+slash ('/') as path separator; and they must be unrooted. $GOROOT (or -goroot)
+must be set to the .zip file directory path containing the Go root directory.
+For instance, for a .zip file created by the command:
+
+	zip -r go.zip $HOME/go
+
+one may run godoc as follows:
+
+	godoc -http=:6060 -zip=go.zip -goroot=$HOME/go
+
+Godoc documentation is converted to HTML or to text using the go/doc package;
+see https://golang.org/pkg/go/doc/#ToHTML for the exact rules.
+Godoc also shows example code that is runnable by the testing package;
+see https://golang.org/pkg/testing/#hdr-Examples for the conventions.
+See "Godoc: documenting Go code" for how to write good comments for godoc:
+https://golang.org/doc/articles/godoc_documenting_go_code.html
+
+Deprecated: godoc cannot select what version of a package is displayed.
+Instead, use golang.org/x/pkgsite/cmd/pkgsite.
+*/
+package main // import "golang.org/x/tools/cmd/godoc"

go/pkg/mod/golang.org/x/tools@v0.24.0/cmd/godoc/godoc_test.go

@@ -0,0 +1,464 @@
+// Copyright 2013 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 main
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"go/build"
+	"io"
+	"net"
+	"net/http"
+	"os"
+	"os/exec"
+	"regexp"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"golang.org/x/tools/go/packages/packagestest"
+	"golang.org/x/tools/internal/testenv"
+)
+
+func TestMain(m *testing.M) {
+	if os.Getenv("GODOC_TEST_IS_GODOC") != "" {
+		main()
+		os.Exit(0)
+	}
+
+	// Inform subprocesses that they should run the cmd/godoc main instead of
+	// running tests. It's a close approximation to building and running the real
+	// command, and much less complicated and expensive to build and clean up.
+	os.Setenv("GODOC_TEST_IS_GODOC", "1")
+
+	os.Exit(m.Run())
+}
+
+var exe struct {
+	path string
+	err  error
+	once sync.Once
+}
+
+func godocPath(t *testing.T) string {
+	if !testenv.HasExec() {
+		t.Skipf("skipping test: exec not supported on %s/%s", runtime.GOOS, runtime.GOARCH)
+	}
+
+	exe.once.Do(func() {
+		exe.path, exe.err = os.Executable()
+	})
+	if exe.err != nil {
+		t.Fatal(exe.err)
+	}
+	return exe.path
+}
+
+func serverAddress(t *testing.T) string {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		ln, err = net.Listen("tcp6", "[::1]:0")
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	return ln.Addr().String()
+}
+
+func waitForServerReady(t *testing.T, ctx context.Context, cmd *exec.Cmd, addr string) {
+	waitForServer(t, ctx,
+		fmt.Sprintf("http://%v/", addr),
+		"Go Documentation Server",
+		false)
+}
+
+func waitForSearchReady(t *testing.T, ctx context.Context, cmd *exec.Cmd, addr string) {
+	waitForServer(t, ctx,
+		fmt.Sprintf("http://%v/search?q=FALLTHROUGH", addr),
+		"The list of tokens.",
+		false)
+}
+
+func waitUntilScanComplete(t *testing.T, ctx context.Context, addr string) {
+	waitForServer(t, ctx,
+		fmt.Sprintf("http://%v/pkg", addr),
+		"Scan is not yet complete",
+		// setting reverse as true, which means this waits
+		// until the string is not returned in the response anymore
+		true)
+}
+
+const pollInterval = 50 * time.Millisecond
+
+// waitForServer waits for server to meet the required condition,
+// failing the test if ctx is canceled before that occurs.
+func waitForServer(t *testing.T, ctx context.Context, url, match string, reverse bool) {
+	start := time.Now()
+	for {
+		if ctx.Err() != nil {
+			t.Helper()
+			t.Fatalf("server failed to respond in %v", time.Since(start))
+		}
+
+		time.Sleep(pollInterval)
+		res, err := http.Get(url)
+		if err != nil {
+			continue
+		}
+		body, err := io.ReadAll(res.Body)
+		res.Body.Close()
+		if err != nil || res.StatusCode != http.StatusOK {
+			continue
+		}
+		switch {
+		case !reverse && bytes.Contains(body, []byte(match)),
+			reverse && !bytes.Contains(body, []byte(match)):
+			return
+		}
+	}
+}
+
+// hasTag checks whether a given release tag is contained in the current version
+// of the go binary.
+func hasTag(t string) bool {
+	for _, v := range build.Default.ReleaseTags {
+		if t == v {
+			return true
+		}
+	}
+	return false
+}
+
+func TestURL(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping on plan9; fails to start up quickly enough")
+	}
+	bin := godocPath(t)
+
+	testcase := func(url string, contents string) func(t *testing.T) {
+		return func(t *testing.T) {
+			stdout, stderr := new(bytes.Buffer), new(bytes.Buffer)
+
+			args := []string{fmt.Sprintf("-url=%s", url)}
+			cmd := testenv.Command(t, bin, args...)
+			cmd.Stdout = stdout
+			cmd.Stderr = stderr
+			cmd.Args[0] = "godoc"
+
+			// Set GOPATH variable to a non-existing absolute path
+			// and GOPROXY=off to disable module fetches.
+			// We cannot just unset GOPATH variable because godoc would default it to ~/go.
+			// (We don't want the indexer looking at the local workspace during tests.)
+			cmd.Env = append(os.Environ(),
+				"GOPATH=/does_not_exist",
+				"GOPROXY=off",
+				"GO111MODULE=off")
+
+			if err := cmd.Run(); err != nil {
+				t.Fatalf("failed to run godoc -url=%q: %s\nstderr:\n%s", url, err, stderr)
+			}
+
+			if !strings.Contains(stdout.String(), contents) {
+				t.Errorf("did not find substring %q in output of godoc -url=%q:\n%s", contents, url, stdout)
+			}
+		}
+	}
+
+	t.Run("index", testcase("/", "These packages are part of the Go Project but outside the main Go tree."))
+	t.Run("fmt", testcase("/pkg/fmt", "Package fmt implements formatted I/O"))
+}
+
+// Basic integration test for godoc HTTP interface.
+func TestWeb(t *testing.T) {
+	bin := godocPath(t)
+
+	for _, x := range packagestest.All {
+		t.Run(x.Name(), func(t *testing.T) {
+			testWeb(t, x, bin, false)
+		})
+	}
+}
+
+// Basic integration test for godoc HTTP interface.
+func TestWebIndex(t *testing.T) {
+	t.Skip("slow test of to-be-deleted code (golang/go#59056)")
+	if testing.Short() {
+		t.Skip("skipping slow test in -short mode")
+	}
+	bin := godocPath(t)
+	testWeb(t, packagestest.GOPATH, bin, true)
+}
+
+// Basic integration test for godoc HTTP interface.
+func testWeb(t *testing.T, x packagestest.Exporter, bin string, withIndex bool) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skip("skipping on plan9: fails to start up quickly enough")
+	case "android", "ios":
+		t.Skip("skipping on mobile: lacks GOROOT/api in test environment")
+	}
+
+	// Write a fake GOROOT/GOPATH with some third party packages.
+	e := packagestest.Export(t, x, []packagestest.Module{
+		{
+			Name: "godoc.test/repo1",
+			Files: map[string]interface{}{
+				"a/a.go": `// Package a is a package in godoc.test/repo1.
+package a; import _ "godoc.test/repo2/a"; const Name = "repo1a"`,
+				"b/b.go": `package b; const Name = "repo1b"`,
+			},
+		},
+		{
+			Name: "godoc.test/repo2",
+			Files: map[string]interface{}{
+				"a/a.go": `package a; const Name = "repo2a"`,
+				"b/b.go": `package b; const Name = "repo2b"`,
+			},
+		},
+	})
+	defer e.Cleanup()
+
+	// Start the server.
+	addr := serverAddress(t)
+	args := []string{fmt.Sprintf("-http=%s", addr)}
+	if withIndex {
+		args = append(args, "-index", "-index_interval=-1s")
+	}
+	cmd := testenv.Command(t, bin, args...)
+	cmd.Dir = e.Config.Dir
+	cmd.Env = e.Config.Env
+	cmdOut := new(strings.Builder)
+	cmd.Stdout = cmdOut
+	cmd.Stderr = cmdOut
+	cmd.Args[0] = "godoc"
+
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("failed to start godoc: %s", err)
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		err := cmd.Wait()
+		t.Logf("%v: %v", cmd, err)
+		cancel()
+	}()
+	defer func() {
+		// Shut down the server cleanly if possible.
+		if runtime.GOOS == "windows" {
+			cmd.Process.Kill() // Windows doesn't support os.Interrupt.
+		} else {
+			cmd.Process.Signal(os.Interrupt)
+		}
+		<-ctx.Done()
+		t.Logf("server output:\n%s", cmdOut)
+	}()
+
+	if withIndex {
+		waitForSearchReady(t, ctx, cmd, addr)
+	} else {
+		waitForServerReady(t, ctx, cmd, addr)
+		waitUntilScanComplete(t, ctx, addr)
+	}
+
+	tests := []struct {
+		path        string
+		contains    []string // substring
+		match       []string // regexp
+		notContains []string
+		needIndex   bool
+		releaseTag  string // optional release tag that must be in go/build.ReleaseTags
+	}{
+		{
+			path: "/",
+			contains: []string{
+				"Go Documentation Server",
+				"Standard library",
+				"These packages are part of the Go Project but outside the main Go tree.",
+			},
+		},
+		{
+			path:     "/pkg/fmt/",
+			contains: []string{"Package fmt implements formatted I/O"},
+		},
+		{
+			path:     "/src/fmt/",
+			contains: []string{"scan_test.go"},
+		},
+		{
+			path:     "/src/fmt/print.go",
+			contains: []string{"// Println formats using"},
+		},
+		{
+			path: "/pkg",
+			contains: []string{
+				"Standard library",
+				"Package fmt implements formatted I/O",
+				"Third party",
+				"Package a is a package in godoc.test/repo1.",
+			},
+			notContains: []string{
+				"internal/syscall",
+				"cmd/gc",
+			},
+		},
+		{
+			path: "/pkg/?m=all",
+			contains: []string{
+				"Standard library",
+				"Package fmt implements formatted I/O",
+				"internal/syscall/?m=all",
+			},
+			notContains: []string{
+				"cmd/gc",
+			},
+		},
+		{
+			path: "/search?q=ListenAndServe",
+			contains: []string{
+				"/src",
+			},
+			notContains: []string{
+				"/pkg/bootstrap",
+			},
+			needIndex: true,
+		},
+		{
+			path: "/pkg/strings/",
+			contains: []string{
+				`href="/src/strings/strings.go"`,
+			},
+		},
+		{
+			path: "/cmd/compile/internal/amd64/",
+			contains: []string{
+				`href="/src/cmd/compile/internal/amd64/ssa.go"`,
+			},
+		},
+		{
+			path: "/pkg/math/bits/",
+			contains: []string{
+				`Added in Go 1.9`,
+			},
+		},
+		{
+			path: "/pkg/net/",
+			contains: []string{
+				`// IPv6 scoped addressing zone; added in Go 1.1`,
+			},
+		},
+		{
+			path: "/pkg/net/http/httptrace/",
+			match: []string{
+				`Got1xxResponse.*// Go 1\.11`,
+			},
+			releaseTag: "go1.11",
+		},
+		// Verify we don't add version info to a struct field added the same time
+		// as the struct itself:
+		{
+			path: "/pkg/net/http/httptrace/",
+			match: []string{
+				`(?m)GotFirstResponseByte func\(\)\s*$`,
+			},
+		},
+		// Remove trailing periods before adding semicolons:
+		{
+			path: "/pkg/database/sql/",
+			contains: []string{
+				"The number of connections currently in use; added in Go 1.11",
+				"The number of idle connections; added in Go 1.11",
+			},
+			releaseTag: "go1.11",
+		},
+
+		// Third party packages.
+		{
+			path:     "/pkg/godoc.test/repo1/a",
+			contains: []string{`const <span id="Name">Name</span> = &#34;repo1a&#34;`},
+		},
+		{
+			path:     "/pkg/godoc.test/repo2/b",
+			contains: []string{`const <span id="Name">Name</span> = &#34;repo2b&#34;`},
+		},
+	}
+	for _, test := range tests {
+		if test.needIndex && !withIndex {
+			continue
+		}
+		url := fmt.Sprintf("http://%s%s", addr, test.path)
+		resp, err := http.Get(url)
+		if err != nil {
+			t.Errorf("GET %s failed: %s", url, err)
+			continue
+		}
+		body, err := io.ReadAll(resp.Body)
+		strBody := string(body)
+		resp.Body.Close()
+		if err != nil {
+			t.Errorf("GET %s: failed to read body: %s (response: %v)", url, err, resp)
+		}
+		isErr := false
+		for _, substr := range test.contains {
+			if test.releaseTag != "" && !hasTag(test.releaseTag) {
+				continue
+			}
+			if !bytes.Contains(body, []byte(substr)) {
+				t.Errorf("GET %s: wanted substring %q in body", url, substr)
+				isErr = true
+			}
+		}
+		for _, re := range test.match {
+			if test.releaseTag != "" && !hasTag(test.releaseTag) {
+				continue
+			}
+			if ok, err := regexp.MatchString(re, strBody); !ok || err != nil {
+				if err != nil {
+					t.Fatalf("Bad regexp %q: %v", re, err)
+				}
+				t.Errorf("GET %s: wanted to match %s in body", url, re)
+				isErr = true
+			}
+		}
+		for _, substr := range test.notContains {
+			if bytes.Contains(body, []byte(substr)) {
+				t.Errorf("GET %s: didn't want substring %q in body", url, substr)
+				isErr = true
+			}
+		}
+		if isErr {
+			t.Errorf("GET %s: got:\n%s", url, body)
+		}
+	}
+}
+
+// Test for golang.org/issue/35476.
+func TestNoMainModule(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in -short mode")
+	}
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping on plan9; for consistency with other tests that build godoc binary")
+	}
+	bin := godocPath(t)
+	tempDir := t.TempDir()
+
+	// Run godoc in an empty directory with module mode explicitly on,
+	// so that 'go env GOMOD' reports os.DevNull.
+	cmd := testenv.Command(t, bin, "-url=/")
+	cmd.Dir = tempDir
+	cmd.Env = append(os.Environ(), "GO111MODULE=on")
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	err := cmd.Run()
+	if err != nil {
+		t.Fatalf("godoc command failed: %v\nstderr=%q", err, stderr.String())
+	}
+	if strings.Contains(stderr.String(), "go mod download") {
+		t.Errorf("stderr contains 'go mod download', is that intentional?\nstderr=%q", stderr.String())
+	}
+}

go/pkg/mod/golang.org/x/tools@v0.24.0/cmd/godoc/goroot.go

@@ -0,0 +1,30 @@
+// 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 main
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+func findGOROOT() string {
+	if env := os.Getenv("GOROOT"); env != "" {
+		return filepath.Clean(env)
+	}
+	def := filepath.Clean(runtime.GOROOT())
+	if runtime.Compiler == "gccgo" {
+		// gccgo has no real GOROOT, and it certainly doesn't
+		// depend on the executable's location.
+		return def
+	}
+	out, err := exec.Command("go", "env", "GOROOT").Output()
+	if err != nil {
+		return def
+	}
+	return strings.TrimSpace(string(out))
+}

go/pkg/mod/golang.org/x/tools@v0.24.0/cmd/godoc/handlers.go

@@ -0,0 +1,98 @@
+// Copyright 2010 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 main
+
+import (
+	"encoding/json"
+	"go/format"
+	"log"
+	"net/http"
+	"text/template"
+
+	"golang.org/x/tools/godoc"
+	"golang.org/x/tools/godoc/redirect"
+	"golang.org/x/tools/godoc/vfs"
+
+	_ "golang.org/x/tools/playground" // register "/compile" playground redirect
+)
+
+var (
+	pres *godoc.Presentation
+	fs   = vfs.NameSpace{}
+)
+
+func registerHandlers(pres *godoc.Presentation) {
+	if pres == nil {
+		panic("nil Presentation")
+	}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
+		if req.URL.Path == "/" {
+			http.Redirect(w, req, "/pkg/", http.StatusFound)
+			return
+		}
+		pres.ServeHTTP(w, req)
+	})
+	mux.Handle("/pkg/C/", redirect.Handler("/cmd/cgo/"))
+	mux.HandleFunc("/fmt", fmtHandler)
+	redirect.Register(mux)
+
+	http.Handle("/", mux)
+}
+
+func readTemplate(name string) *template.Template {
+	if pres == nil {
+		panic("no global Presentation set yet")
+	}
+	path := "lib/godoc/" + name
+
+	// use underlying file system fs to read the template file
+	// (cannot use template ParseFile functions directly)
+	data, err := vfs.ReadFile(fs, path)
+	if err != nil {
+		log.Fatal("readTemplate: ", err)
+	}
+	// be explicit with errors (for app engine use)
+	t, err := template.New(name).Funcs(pres.FuncMap()).Parse(string(data))
+	if err != nil {
+		log.Fatal("readTemplate: ", err)
+	}
+	return t
+}
+
+func readTemplates(p *godoc.Presentation) {
+	p.CallGraphHTML = readTemplate("callgraph.html")
+	p.DirlistHTML = readTemplate("dirlist.html")
+	p.ErrorHTML = readTemplate("error.html")
+	p.ExampleHTML = readTemplate("example.html")
+	p.GodocHTML = readTemplate("godoc.html")
+	p.ImplementsHTML = readTemplate("implements.html")
+	p.MethodSetHTML = readTemplate("methodset.html")
+	p.PackageHTML = readTemplate("package.html")
+	p.PackageRootHTML = readTemplate("packageroot.html")
+	p.SearchHTML = readTemplate("search.html")
+	p.SearchDocHTML = readTemplate("searchdoc.html")
+	p.SearchCodeHTML = readTemplate("searchcode.html")
+	p.SearchTxtHTML = readTemplate("searchtxt.html")
+}
+
+type fmtResponse struct {
+	Body  string
+	Error string
+}
+
+// fmtHandler takes a Go program in its "body" form value, formats it with
+// standard gofmt formatting, and writes a fmtResponse as a JSON object.
+func fmtHandler(w http.ResponseWriter, r *http.Request) {
+	resp := new(fmtResponse)
+	body, err := format.Source([]byte(r.FormValue("body")))
+	if err != nil {
+		resp.Error = err.Error()
+	} else {
+		resp.Body = string(body)
+	}
+	w.Header().Set("Content-type", "application/json; charset=utf-8")
+	json.NewEncoder(w).Encode(resp)
+}

go/pkg/mod/golang.org/x/tools@v0.24.0/cmd/godoc/main.go

@@ -0,0 +1,504 @@
+// Copyright 2009 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.
+
+// godoc: Go Documentation Server
+
+// Web server tree:
+//
+//	http://godoc/		redirect to /pkg/
+//	http://godoc/src/	serve files from $GOROOT/src; .go gets pretty-printed
+//	http://godoc/cmd/	serve documentation about commands
+//	http://godoc/pkg/	serve documentation about packages
+//				(idea is if you say import "compress/zlib", you go to
+//				http://godoc/pkg/compress/zlib)
+//
+
+package main
+
+import (
+	"archive/zip"
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	_ "expvar" // to serve /debug/vars
+	"flag"
+	"fmt"
+	"go/build"
+	"io"
+	"log"
+	"net/http"
+	_ "net/http/pprof" // to serve /debug/pprof/*
+	"net/url"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+
+	"golang.org/x/tools/godoc"
+	"golang.org/x/tools/godoc/static"
+	"golang.org/x/tools/godoc/vfs"
+	"golang.org/x/tools/godoc/vfs/gatefs"
+	"golang.org/x/tools/godoc/vfs/mapfs"
+	"golang.org/x/tools/godoc/vfs/zipfs"
+	"golang.org/x/tools/internal/gocommand"
+)
+
+const defaultAddr = "localhost:6060" // default webserver address
+
+var (
+	// file system to serve
+	// (with e.g.: zip -r go.zip $GOROOT -i \*.go -i \*.html -i \*.css -i \*.js -i \*.txt -i \*.c -i \*.h -i \*.s -i \*.png -i \*.jpg -i \*.sh -i favicon.ico)
+	zipfile = flag.String("zip", "", "zip file providing the file system to serve; disabled if empty")
+
+	// file-based index
+	writeIndex = flag.Bool("write_index", false, "write index to a file; the file name must be specified with -index_files")
+
+	// network
+	httpAddr = flag.String("http", defaultAddr, "HTTP service address")
+
+	// layout control
+	urlFlag = flag.String("url", "", "print HTML for named URL")
+
+	verbose = flag.Bool("v", false, "verbose mode")
+
+	// file system roots
+	// TODO(gri) consider the invariant that goroot always end in '/'
+	goroot = flag.String("goroot", findGOROOT(), "Go root directory")
+
+	// layout control
+	showTimestamps = flag.Bool("timestamps", false, "show timestamps with directory listings")
+	templateDir    = flag.String("templates", "", "load templates/JS/CSS from disk in this directory")
+	showPlayground = flag.Bool("play", false, "enable playground")
+	declLinks      = flag.Bool("links", true, "link identifiers to their declarations")
+
+	// search index
+	indexEnabled  = flag.Bool("index", false, "enable search index")
+	indexFiles    = flag.String("index_files", "", "glob pattern specifying index files; if not empty, the index is read from these files in sorted order")
+	indexInterval = flag.Duration("index_interval", 0, "interval of indexing; 0 for default (5m), negative to only index once at startup")
+	maxResults    = flag.Int("maxresults", 10000, "maximum number of full text search results shown")
+	indexThrottle = flag.Float64("index_throttle", 0.75, "index throttle value; 0.0 = no time allocated, 1.0 = full throttle")
+
+	// source code notes
+	notesRx = flag.String("notes", "BUG", "regular expression matching note markers to show")
+)
+
+// An httpResponseRecorder is an http.ResponseWriter
+type httpResponseRecorder struct {
+	body   *bytes.Buffer
+	header http.Header
+	code   int
+}
+
+func (w *httpResponseRecorder) Header() http.Header         { return w.header }
+func (w *httpResponseRecorder) Write(b []byte) (int, error) { return w.body.Write(b) }
+func (w *httpResponseRecorder) WriteHeader(code int)        { w.code = code }
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: godoc -http="+defaultAddr+"\n")
+	flag.PrintDefaults()
+	os.Exit(2)
+}
+
+func loggingHandler(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		log.Printf("%s\t%s", req.RemoteAddr, req.URL)
+		h.ServeHTTP(w, req)
+	})
+}
+
+func handleURLFlag() {
+	// Try up to 10 fetches, following redirects.
+	urlstr := *urlFlag
+	for i := 0; i < 10; i++ {
+		// Prepare request.
+		u, err := url.Parse(urlstr)
+		if err != nil {
+			log.Fatal(err)
+		}
+		req := &http.Request{
+			URL: u,
+		}
+
+		// Invoke default HTTP handler to serve request
+		// to our buffering httpWriter.
+		w := &httpResponseRecorder{code: 200, header: make(http.Header), body: new(bytes.Buffer)}
+		http.DefaultServeMux.ServeHTTP(w, req)
+
+		// Return data, error, or follow redirect.
+		switch w.code {
+		case 200: // ok
+			os.Stdout.Write(w.body.Bytes())
+			return
+		case 301, 302, 303, 307: // redirect
+			redirect := w.header.Get("Location")
+			if redirect == "" {
+				log.Fatalf("HTTP %d without Location header", w.code)
+			}
+			urlstr = redirect
+		default:
+			log.Fatalf("HTTP error %d", w.code)
+		}
+	}
+	log.Fatalf("too many redirects")
+}
+
+func initCorpus(corpus *godoc.Corpus) {
+	err := corpus.Init()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+
+	// Check usage.
+	if flag.NArg() > 0 {
+		fmt.Fprintln(os.Stderr, `Unexpected arguments. Use "go doc" for command-line help output instead. For example, "go doc fmt.Printf".`)
+		usage()
+	}
+	if *httpAddr == "" && *urlFlag == "" && !*writeIndex {
+		fmt.Fprintln(os.Stderr, "At least one of -http, -url, or -write_index must be set to a non-zero value.")
+		usage()
+	}
+
+	// Set the resolved goroot.
+	vfs.GOROOT = *goroot
+
+	fsGate := make(chan bool, 20)
+
+	// Determine file system to use.
+	if *zipfile == "" {
+		// use file system of underlying OS
+		rootfs := gatefs.New(vfs.OS(*goroot), fsGate)
+		fs.Bind("/", rootfs, "/", vfs.BindReplace)
+	} else {
+		// use file system specified via .zip file (path separator must be '/')
+		rc, err := zip.OpenReader(*zipfile)
+		if err != nil {
+			log.Fatalf("%s: %s\n", *zipfile, err)
+		}
+		defer rc.Close() // be nice (e.g., -writeIndex mode)
+		fs.Bind("/", zipfs.New(rc, *zipfile), *goroot, vfs.BindReplace)
+	}
+	if *templateDir != "" {
+		fs.Bind("/lib/godoc", vfs.OS(*templateDir), "/", vfs.BindBefore)
+		fs.Bind("/favicon.ico", vfs.OS(*templateDir), "/favicon.ico", vfs.BindReplace)
+	} else {
+		fs.Bind("/lib/godoc", mapfs.New(static.Files), "/", vfs.BindReplace)
+		fs.Bind("/favicon.ico", mapfs.New(static.Files), "/favicon.ico", vfs.BindReplace)
+	}
+
+	// Get the GOMOD value, use it to determine if godoc is being invoked in module mode.
+	goModFile, err := goMod()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to determine go env GOMOD value: %v", err)
+		goModFile = "" // Fall back to GOPATH mode.
+	}
+
+	if goModFile != "" {
+		fmt.Printf("using module mode; GOMOD=%s\n", goModFile)
+
+		// Detect whether to use vendor mode or not.
+		vendorEnabled, mainModVendor, err := gocommand.VendorEnabled(context.Background(), gocommand.Invocation{}, &gocommand.Runner{})
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to determine if vendoring is enabled: %v", err)
+			os.Exit(1)
+		}
+		if vendorEnabled {
+			// Bind the root directory of the main module.
+			fs.Bind(path.Join("/src", mainModVendor.Path), gatefs.New(vfs.OS(mainModVendor.Dir), fsGate), "/", vfs.BindAfter)
+
+			// Bind the vendor directory.
+			//
+			// Note that in module mode, vendor directories in locations
+			// other than the main module's root directory are ignored.
+			// See https://golang.org/ref/mod#vendoring.
+			vendorDir := filepath.Join(mainModVendor.Dir, "vendor")
+			fs.Bind("/src", gatefs.New(vfs.OS(vendorDir), fsGate), "/", vfs.BindAfter)
+
+		} else {
+			// Try to download dependencies that are not in the module cache in order to
+			// show their documentation.
+			// This may fail if module downloading is disallowed (GOPROXY=off) or due to
+			// limited connectivity, in which case we print errors to stderr and show
+			// documentation only for packages that are available.
+			fillModuleCache(os.Stderr, goModFile)
+
+			// Determine modules in the build list.
+			mods, err := buildList(goModFile)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "failed to determine the build list of the main module: %v", err)
+				os.Exit(1)
+			}
+
+			// Bind module trees into Go root.
+			for _, m := range mods {
+				if m.Dir == "" {
+					// Module is not available in the module cache, skip it.
+					continue
+				}
+				dst := path.Join("/src", m.Path)
+				fs.Bind(dst, gatefs.New(vfs.OS(m.Dir), fsGate), "/", vfs.BindAfter)
+			}
+		}
+	} else {
+		fmt.Println("using GOPATH mode")
+
+		// Bind $GOPATH trees into Go root.
+		for _, p := range filepath.SplitList(build.Default.GOPATH) {
+			fs.Bind("/src", gatefs.New(vfs.OS(p), fsGate), "/src", vfs.BindAfter)
+		}
+	}
+
+	var corpus *godoc.Corpus
+	if goModFile != "" {
+		corpus = godoc.NewCorpus(moduleFS{fs})
+	} else {
+		corpus = godoc.NewCorpus(fs)
+	}
+	corpus.Verbose = *verbose
+	corpus.MaxResults = *maxResults
+	corpus.IndexEnabled = *indexEnabled
+	if *maxResults == 0 {
+		corpus.IndexFullText = false
+	}
+	corpus.IndexFiles = *indexFiles
+	corpus.IndexDirectory = func(dir string) bool {
+		return dir != "/pkg" && !strings.HasPrefix(dir, "/pkg/")
+	}
+	corpus.IndexThrottle = *indexThrottle
+	corpus.IndexInterval = *indexInterval
+	if *writeIndex || *urlFlag != "" {
+		corpus.IndexThrottle = 1.0
+		corpus.IndexEnabled = true
+		initCorpus(corpus)
+	} else {
+		go initCorpus(corpus)
+	}
+
+	// Initialize the version info before readTemplates, which saves
+	// the map value in a method value.
+	corpus.InitVersionInfo()
+
+	pres = godoc.NewPresentation(corpus)
+	pres.ShowTimestamps = *showTimestamps
+	pres.ShowPlayground = *showPlayground
+	pres.DeclLinks = *declLinks
+	if *notesRx != "" {
+		pres.NotesRx = regexp.MustCompile(*notesRx)
+	}
+
+	readTemplates(pres)
+	registerHandlers(pres)
+
+	if *writeIndex {
+		// Write search index and exit.
+		if *indexFiles == "" {
+			log.Fatal("no index file specified")
+		}
+
+		log.Println("initialize file systems")
+		*verbose = true // want to see what happens
+
+		corpus.UpdateIndex()
+
+		log.Println("writing index file", *indexFiles)
+		f, err := os.Create(*indexFiles)
+		if err != nil {
+			log.Fatal(err)
+		}
+		index, _ := corpus.CurrentIndex()
+		_, err = index.WriteTo(f)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		log.Println("done")
+		return
+	}
+
+	// Print content that would be served at the URL *urlFlag.
+	if *urlFlag != "" {
+		handleURLFlag()
+		return
+	}
+
+	var handler http.Handler = http.DefaultServeMux
+	if *verbose {
+		log.Printf("Go Documentation Server")
+		log.Printf("version = %s", runtime.Version())
+		log.Printf("address = %s", *httpAddr)
+		log.Printf("goroot = %s", *goroot)
+		switch {
+		case !*indexEnabled:
+			log.Print("search index disabled")
+		case *maxResults > 0:
+			log.Printf("full text index enabled (maxresults = %d)", *maxResults)
+		default:
+			log.Print("identifier search index enabled")
+		}
+		fs.Fprint(os.Stderr)
+		handler = loggingHandler(handler)
+	}
+
+	// Initialize search index.
+	if *indexEnabled {
+		go corpus.RunIndexer()
+	}
+
+	// Start http server.
+	if *verbose {
+		log.Println("starting HTTP server")
+	}
+	if err := http.ListenAndServe(*httpAddr, handler); err != nil {
+		log.Fatalf("ListenAndServe %s: %v", *httpAddr, err)
+	}
+}
+
+// goMod returns the go env GOMOD value in the current directory
+// by invoking the go command.
+//
+// GOMOD is documented at https://golang.org/cmd/go/#hdr-Environment_variables:
+//
+//	The absolute path to the go.mod of the main module,
+//	or the empty string if not using modules.
+func goMod() (string, error) {
+	out, err := exec.Command("go", "env", "-json", "GOMOD").Output()
+	if ee := (*exec.ExitError)(nil); errors.As(err, &ee) {
+		return "", fmt.Errorf("go command exited unsuccessfully: %v\n%s", ee.ProcessState.String(), ee.Stderr)
+	} else if err != nil {
+		return "", err
+	}
+	var env struct {
+		GoMod string
+	}
+	err = json.Unmarshal(out, &env)
+	if err != nil {
+		return "", err
+	}
+	return env.GoMod, nil
+}
+
+// fillModuleCache does a best-effort attempt to fill the module cache
+// with all dependencies of the main module in the current directory
+// by invoking the go command. Module download logs are streamed to w.
+// If there are any problems encountered, they are also written to w.
+// It should only be used in module mode, when vendor mode isn't on.
+//
+// See https://golang.org/cmd/go/#hdr-Download_modules_to_local_cache.
+func fillModuleCache(w io.Writer, goMod string) {
+	if goMod == os.DevNull {
+		// No module requirements, nothing to do.
+		return
+	}
+
+	cmd := exec.Command("go", "mod", "download", "-json")
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	cmd.Stderr = w
+	err := cmd.Run()
+	if ee := (*exec.ExitError)(nil); errors.As(err, &ee) && ee.ExitCode() == 1 {
+		// Exit code 1 from this command means there were some
+		// non-empty Error values in the output. Print them to w.
+		fmt.Fprintf(w, "documentation for some packages is not shown:\n")
+		for dec := json.NewDecoder(&out); ; {
+			var m struct {
+				Path    string // Module path.
+				Version string // Module version.
+				Error   string // Error loading module.
+			}
+			err := dec.Decode(&m)
+			if err == io.EOF {
+				break
+			} else if err != nil {
+				fmt.Fprintf(w, "error decoding JSON object from go mod download -json: %v\n", err)
+				continue
+			}
+			if m.Error == "" {
+				continue
+			}
+			fmt.Fprintf(w, "\tmodule %s@%s is not in the module cache and there was a problem downloading it: %s\n", m.Path, m.Version, m.Error)
+		}
+	} else if err != nil {
+		fmt.Fprintf(w, "there was a problem filling module cache: %v\n", err)
+	}
+}
+
+type mod struct {
+	Path string // Module path.
+	Dir  string // Directory holding files for this module, if any.
+}
+
+// buildList determines the build list in the current directory
+// by invoking the go command. It should only be used in module mode,
+// when vendor mode isn't on.
+//
+// See https://golang.org/cmd/go/#hdr-The_main_module_and_the_build_list.
+func buildList(goMod string) ([]mod, error) {
+	if goMod == os.DevNull {
+		// Empty build list.
+		return nil, nil
+	}
+
+	out, err := exec.Command("go", "list", "-m", "-json", "all").Output()
+	if ee := (*exec.ExitError)(nil); errors.As(err, &ee) {
+		return nil, fmt.Errorf("go command exited unsuccessfully: %v\n%s", ee.ProcessState.String(), ee.Stderr)
+	} else if err != nil {
+		return nil, err
+	}
+	var mods []mod
+	for dec := json.NewDecoder(bytes.NewReader(out)); ; {
+		var m mod
+		err := dec.Decode(&m)
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+		mods = append(mods, m)
+	}
+	return mods, nil
+}
+
+// moduleFS is a vfs.FileSystem wrapper used when godoc is running
+// in module mode. It's needed so that packages inside modules are
+// considered to be third party.
+//
+// It overrides the RootType method of the underlying filesystem
+// and implements it using a heuristic based on the import path.
+// If the first element of the import path does not contain a dot,
+// that package is considered to be inside GOROOT. If it contains
+// a dot, then that package is considered to be third party.
+//
+// TODO(dmitshur): The RootType abstraction works well when GOPATH
+// workspaces are bound at their roots, but scales poorly in the
+// general case. It should be replaced by a more direct solution
+// for determining whether a package is third party or not.
+type moduleFS struct{ vfs.FileSystem }
+
+func (moduleFS) RootType(path string) vfs.RootType {
+	if !strings.HasPrefix(path, "/src/") {
+		return ""
+	}
+	domain := path[len("/src/"):]
+	if i := strings.Index(domain, "/"); i >= 0 {
+		domain = domain[:i]
+	}
+	if !strings.Contains(domain, ".") {
+		// No dot in the first element of import path
+		// suggests this is a package in GOROOT.
+		return vfs.RootTypeGoRoot
+	} else {
+		// A dot in the first element of import path
+		// suggests this is a third party package.
+		return vfs.RootTypeGoPath
+	}
+}
+func (fs moduleFS) String() string { return "module(" + fs.FileSystem.String() + ")" }