whatcanGOwrong

go/pkg/mod/golang.org/x/telemetry@v0.0.0-20240829154258-f29ab539cc98/internal/unionfs/testdata/dir1/file1

@@ -0,0 +1 @@
+file 1 content from dir 1

go/pkg/mod/golang.org/x/telemetry@v0.0.0-20240829154258-f29ab539cc98/internal/unionfs/testdata/dir2/file1

@@ -0,0 +1 @@
+file 1 content from dir 2

go/pkg/mod/golang.org/x/telemetry@v0.0.0-20240829154258-f29ab539cc98/internal/unionfs/testdata/dir2/file2

@@ -0,0 +1 @@
+file 2 content

go/pkg/mod/golang.org/x/telemetry@v0.0.0-20240829154258-f29ab539cc98/internal/unionfs/unionfs.go

@@ -0,0 +1,82 @@
+// Copyright 2023 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 unionfs allows multiple file systems to be read as a union.
+package unionfs
+
+import (
+	"io/fs"
+)
+
+var _ fs.ReadDirFS = FS{}
+
+// A FS is an FS presenting the union of the file systems in the slice. If
+// multiple file systems provide a particular file, Open uses the FS listed
+// earlier in the slice.
+type FS []fs.FS
+
+// Sub returns an FS corresponding to the merged subtree rooted at a set of
+// fsys's dirs.
+func Sub(fsys fs.FS, dirs ...string) (FS, error) {
+	var subs FS
+	for _, dir := range dirs {
+		if _, err := fs.Stat(fsys, dir); err != nil {
+			return nil, err
+		}
+		sub, err := fs.Sub(fsys, dir)
+		if err != nil {
+			return nil, err
+		}
+		subs = append(subs, sub)
+	}
+	return subs, nil
+}
+
+func (fsys FS) Open(name string) (fs.File, error) {
+	var errOut error
+	for _, sub := range fsys {
+		f, err := sub.Open(name)
+		if err == nil {
+			return f, nil
+		}
+		if errOut == nil {
+			errOut = err
+		}
+	}
+	return nil, errOut
+}
+
+func (fsys FS) ReadDir(name string) ([]fs.DirEntry, error) {
+	var all []fs.DirEntry
+	var seen map[string]bool // seen[name] is true if name is listed in all; lazily initialized
+	var errOut error
+	for _, sub := range fsys {
+		list, err := fs.ReadDir(sub, name)
+		if err != nil {
+			errOut = err
+		}
+		if len(all) == 0 {
+			all = append(all, list...)
+		} else {
+			if seen == nil {
+				// Initialize seen only after we get two different directory listings.
+				seen = make(map[string]bool)
+				for _, d := range all {
+					seen[d.Name()] = true
+				}
+			}
+			for _, d := range list {
+				name := d.Name()
+				if !seen[name] {
+					seen[name] = true
+					all = append(all, d)
+				}
+			}
+		}
+	}
+	if len(all) > 0 {
+		return all, nil
+	}
+	return nil, errOut
+}

go/pkg/mod/golang.org/x/telemetry@v0.0.0-20240829154258-f29ab539cc98/internal/unionfs/unionfs_test.go

@@ -0,0 +1,113 @@
+// Copyright 2023 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 unionfs
+
+import (
+	"io"
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestFS_Open(t *testing.T) {
+	fsys, err := Sub(os.DirFS("testdata"), "dir1", "dir2")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type args struct {
+		name string
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    string
+		wantErr bool
+	}{
+		{
+			name: "file1 from dir1",
+			args: args{
+				name: "file1",
+			},
+			want:    "file 1 content from dir 1\n",
+			wantErr: false,
+		},
+		{
+			name: "file2 from dir2",
+			args: args{
+				name: "file2",
+			},
+			want:    "file 2 content\n",
+			wantErr: false,
+		},
+		{
+			name: "file not found",
+			args: args{
+				name: "file3",
+			},
+			want:    "file3",
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			file, err := fsys.Open(tt.args.name)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("FS.Open() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				bytes, err := io.ReadAll(file)
+				if err != nil {
+					t.Fatal(err)
+				}
+				got := string(bytes)
+				if got != tt.want {
+					t.Errorf("FS.Open() = %v, want %v", got, tt.want)
+				}
+			}
+		})
+	}
+}
+
+func TestFS_ReadDir(t *testing.T) {
+	var err error
+	fsys, err := Sub(os.DirFS("testdata"), "dir1", "dir2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	type args struct {
+		name string
+	}
+	tests := []struct {
+		name      string
+		args      args
+		fsys      FS
+		wantFiles []string
+	}{
+		{
+			name:      "",
+			args:      args{"."},
+			fsys:      fsys,
+			wantFiles: []string{"file1", "file2"},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			dirs, err := tt.fsys.ReadDir(tt.args.name)
+			if err != nil {
+				t.Errorf("FS.ReadDir() error = %v", err)
+				return
+			}
+			var got []string
+			for _, v := range dirs {
+				got = append(got, v.Name())
+			}
+			if !reflect.DeepEqual(got, tt.wantFiles) {
+				t.Errorf("FS.ReadDir() = %v, want %v", got, tt.wantFiles)
+			}
+		})
+	}
+}