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Add chroot support to embedfs using billy's chroot helper
- Remove memfs dependency and use local sorting for ReadDir - Implement chroot support by wrapping embedfs with chroot.New() in New() - Add comprehensive chroot tests covering read-only operations - Follow same pattern as memfs and osfs for consistent API - Maintain read-only behavior - write operations still return ErrReadOnly This enables embedfs to work with filesystem abstractions that require chroot support for path isolation.
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‎embedfs/chroot_test.go‎

Lines changed: 294 additions & 0 deletions
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package embedfs
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import (
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"io"
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"testing"
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"github.com/go-git/go-billy/v6"
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"github.com/go-git/go-billy/v6/embedfs_testdata"
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"github.com/stretchr/testify/assert"
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"github.com/stretchr/testify/require"
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)
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func TestChroot_Basic(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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// Test chroot to existing directory
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chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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require.NotNil(t, chrootFS)
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// Test that we can access files in the chrooted filesystem
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f, err := chrootFS.Open("file1.txt")
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require.NoError(t, err)
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defer f.Close()
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content, err := io.ReadAll(f)
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require.NoError(t, err)
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assert.Equal(t, "Hello from embedfs!", string(content))
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}
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func TestChroot_NestedDirectory(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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// Test chroot to nested directory
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chrootFS, err := fs.Chroot("testdata/subdir")
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require.NoError(t, err)
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require.NotNil(t, chrootFS)
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// Test that we can access nested files from the chrooted root
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f, err := chrootFS.Open("nested.txt")
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require.NoError(t, err)
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defer f.Close()
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content, err := io.ReadAll(f)
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require.NoError(t, err)
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assert.Equal(t, "Nested file content", string(content))
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}
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func TestChroot_StatInChroot(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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// Test stat on files that exist in chrooted directory
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fi, err := chrootFS.Stat("file1.txt")
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require.NoError(t, err)
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assert.Equal(t, "file1.txt", fi.Name())
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assert.False(t, fi.IsDir())
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// Test stat on directories that exist in chrooted directory
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fi, err = chrootFS.Stat("subdir")
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require.NoError(t, err)
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assert.Equal(t, "subdir", fi.Name())
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assert.True(t, fi.IsDir())
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// Test stat with absolute path in chrooted filesystem
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fi, err = chrootFS.Stat("/file2.txt")
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require.NoError(t, err)
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assert.Equal(t, "file2.txt", fi.Name())
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assert.False(t, fi.IsDir())
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}
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func TestChroot_ReadDirInChroot(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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// Test reading directory contents from chrooted root
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entries, err := chrootFS.ReadDir("/")
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require.NoError(t, err)
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expectedFiles := []string{"empty.txt", "file1.txt", "file2.txt", "subdir"}
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assert.Len(t, entries, len(expectedFiles))
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foundFiles := make(map[string]bool)
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for _, entry := range entries {
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foundFiles[entry.Name()] = true
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}
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for _, expected := range expectedFiles {
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assert.True(t, foundFiles[expected], "Expected file %s not found", expected)
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}
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// Test reading subdirectory from chrooted filesystem
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entries, err = chrootFS.ReadDir("subdir")
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require.NoError(t, err)
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assert.Len(t, entries, 1)
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assert.Equal(t, "nested.txt", entries[0].Name())
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}
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func TestChroot_PathNormalization(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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// Test chroot with different path formats
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tests := []struct {
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name string
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chrootPath string
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openPath string
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expectFile string
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}{
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{
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name: "absolute chroot path",
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chrootPath: "/testdata",
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openPath: "file1.txt",
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expectFile: "file1.txt",
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},
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{
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name: "relative chroot path",
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chrootPath: "testdata",
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openPath: "file1.txt",
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expectFile: "file1.txt",
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},
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{
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name: "absolute open path in chroot",
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chrootPath: "testdata",
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openPath: "/file1.txt",
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expectFile: "file1.txt",
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},
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{
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name: "nested chroot",
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chrootPath: "testdata/subdir",
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openPath: "nested.txt",
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expectFile: "nested.txt",
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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chrootFS, err := fs.Chroot(tt.chrootPath)
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require.NoError(t, err)
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f, err := chrootFS.Open(tt.openPath)
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require.NoError(t, err)
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defer f.Close()
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assert.Equal(t, tt.expectFile, f.Name())
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})
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}
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}
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func TestChroot_NonExistentPath(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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// Test chroot to non-existent directory - billy's chroot helper allows this
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chrootFS, err := fs.Chroot("nonexistent")
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require.NoError(t, err)
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require.NotNil(t, chrootFS)
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// But accessing files within the non-existent chroot should fail
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_, err = chrootFS.Open("anyfile.txt")
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assert.Error(t, err)
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}
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func TestChroot_Join(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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// Test Join operation in chrooted filesystem
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joined := chrootFS.Join("subdir", "nested.txt")
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assert.Equal(t, "subdir/nested.txt", joined)
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// Test that joined path can be used to open file
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f, err := chrootFS.Open(joined)
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require.NoError(t, err)
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defer f.Close()
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content, err := io.ReadAll(f)
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require.NoError(t, err)
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assert.Equal(t, "Nested file content", string(content))
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}
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func TestChroot_UnsupportedOperations(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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// Test that write operations still fail in chrooted embedfs
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_, err = chrootFS.Create("newfile.txt")
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require.ErrorIs(t, err, billy.ErrReadOnly)
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err = chrootFS.Remove("file1.txt")
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require.ErrorIs(t, err, billy.ErrReadOnly)
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err = chrootFS.Rename("file1.txt", "renamed.txt")
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require.ErrorIs(t, err, billy.ErrReadOnly)
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err = chrootFS.MkdirAll("newdir", 0755)
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require.ErrorIs(t, err, billy.ErrReadOnly)
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}
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func TestChroot_NestedChroot(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
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// Test creating nested chrootfs
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firstChroot, err := fs.Chroot("testdata")
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require.NoError(t, err)
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secondChroot, err := firstChroot.Chroot("subdir")
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require.NoError(t, err)
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// Test that nested chroot works correctly
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f, err := secondChroot.Open("nested.txt")
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require.NoError(t, err)
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defer f.Close()
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content, err := io.ReadAll(f)
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require.NoError(t, err)
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assert.Equal(t, "Nested file content", string(content))
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// Test that we can't access parent directory from nested chroot
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entries, err := secondChroot.ReadDir("/")
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require.NoError(t, err)
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assert.Len(t, entries, 1)
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assert.Equal(t, "nested.txt", entries[0].Name())
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}
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func TestChroot_FileOperations(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
252+
chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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// Test file operations in chrooted filesystem
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f, err := chrootFS.Open("file2.txt")
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require.NoError(t, err)
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defer f.Close()
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// Test Read
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buf := make([]byte, 10)
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n, err := f.Read(buf)
263+
require.NoError(t, err)
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assert.Equal(t, "Another te", string(buf[:n]))
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// Test Seek
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_, err = f.Seek(0, io.SeekStart)
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require.NoError(t, err)
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// Test ReadAt
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buf2 := make([]byte, 7)
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n, err = f.ReadAt(buf2, 8)
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require.NoError(t, err)
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assert.Equal(t, "test fi", string(buf2[:n]))
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// Test that file position wasn't affected by ReadAt
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n, err = f.Read(buf)
278+
require.NoError(t, err)
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assert.Equal(t, "Another te", string(buf[:n]))
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}
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func TestChroot_Lstat(t *testing.T) {
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t.Parallel()
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fs := New(embedfs_testdata.GetTestData())
286+
chrootFS, err := fs.Chroot("testdata")
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require.NoError(t, err)
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// Test Lstat in chrooted filesystem (should behave same as Stat for embedfs)
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fi, err := chrootFS.Lstat("file1.txt")
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require.NoError(t, err)
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assert.Equal(t, "file1.txt", fi.Name())
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assert.False(t, fi.IsDir())
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}

‎embedfs/embed.go‎

Lines changed: 6 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@ import (
1313
"sync"
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1515
"github.com/go-git/go-billy/v6"
16-
"github.com/go-git/go-billy/v6/memfs"
16+
"github.com/go-git/go-billy/v6/helper/chroot"
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)
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type Embed struct {
@@ -29,7 +29,7 @@ func New(efs *embed.FS) billy.Filesystem {
2929
fs.underlying = &embed.FS{}
3030
}
3131

32-
return fs
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return chroot.New(fs, "/")
3333
}
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3535
// normalizePath converts billy's absolute paths to embed.FS relative paths
@@ -120,17 +120,14 @@ func (fs *Embed) ReadDir(path string) ([]os.FileInfo, error) {
120120
entries = append(entries, fi)
121121
}
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123-
sort.Sort(memfs.ByName(entries))
123+
sort.Slice(entries, func(i, j int) bool {
124+
return entries[i].Name() < entries[j].Name()
125+
})
124126

125127
return entries, nil
126128
}
127129

128-
// Chroot is not supported.
129-
//
130-
// Calls will always return billy.ErrNotSupported.
131-
func (fs *Embed) Chroot(_ string) (billy.Filesystem, error) {
132-
return nil, billy.ErrNotSupported
133-
}
130+
134131

135132
// Lstat behaves the same as Stat for embedded filesystems since there are no symlinks.
136133
func (fs *Embed) Lstat(filename string) (os.FileInfo, error) {

‎go.mod‎

Lines changed: 2 additions & 0 deletions
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@@ -14,3 +14,5 @@ require (
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github.com/pmezard/go-difflib v1.0.0 // indirect
1515
gopkg.in/yaml.v3 v3.0.1 // indirect
1616
)
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replace github.com/go-git/go-billy/v6 => github.com/this-kirke/go-billy/v6 v6.0.0

‎go.sum‎

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Original file line numberDiff line numberDiff line change
@@ -2,6 +2,7 @@ github.com/cyphar/filepath-securejoin v0.4.1 h1:JyxxyPEaktOD+GAnqIqTf9A8tHyAG22r
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github.com/cyphar/filepath-securejoin v0.4.1/go.mod h1:Sdj7gXlvMcPZsbhwhQ33GguGLDGQL7h7bg04C/+u9jI=
33
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
44
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
5+
github.com/go-git/go-billy/v6 v6.0.0-20250711053805-c1f149aaab07/go.mod h1:Pa0/zeE0tC0GiZLFFtOYXOky9SgpNF+zkrj7aEJhBVg=
56
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
67
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
78
github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=

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