os: add implementation of fs.ReadLinkFS to *rootFS

Fixes #73887

Change-Id: I43f3f4324d740b5381615bce864b7ec31415a635
Reviewed-on: https://go-review.googlesource.com/c/go/+/676135
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

diff --git a/src/os/root.go b/src/os/root.go
index 953cd6b9b963dc3ab9da8356c088ba6e0427baf7..d759727ce7a89bce79d67979a51e46c2c7dc8bf3 100644 (file)
--- a/src/os/root.go
+++ b/src/os/root.go
@@ -352,8 +352,8 @@ func splitPathInRoot(s string, prefix, suffix []string) (_ []string, suffixSep s
 
 // FS returns a file system (an fs.FS) for the tree of files in the root.
 //
-// The result implements [io/fs.StatFS], [io/fs.ReadFileFS] and
-// [io/fs.ReadDirFS].
+// The result implements [io/fs.StatFS], [io/fs.ReadFileFS],
+// [io/fs.ReadDirFS], and [io/fs.ReadLinkFS].
 func (r *Root) FS() fs.FS {
        return (*rootFS)(r)
 }
@@ -409,6 +409,14 @@ func (rfs *rootFS) ReadFile(name string) ([]byte, error) {
        return readFileContents(statOrZero(f), f.Read)
 }
 
+func (rfs *rootFS) ReadLink(name string) (string, error) {
+       r := (*Root)(rfs)
+       if !isValidRootFSPath(name) {
+               return "", &PathError{Op: "readlink", Path: name, Err: ErrInvalid}
+       }
+       return r.Readlink(name)
+}
+
 func (rfs *rootFS) Stat(name string) (FileInfo, error) {
        r := (*Root)(rfs)
        if !isValidRootFSPath(name) {
@@ -417,6 +425,14 @@ func (rfs *rootFS) Stat(name string) (FileInfo, error) {
        return r.Stat(name)
 }
 
+func (rfs *rootFS) Lstat(name string) (FileInfo, error) {
+       r := (*Root)(rfs)
+       if !isValidRootFSPath(name) {
+               return nil, &PathError{Op: "lstat", Path: name, Err: ErrInvalid}
+       }
+       return r.Lstat(name)
+}
+
 // isValidRootFSPath reports whether name is a valid filename to pass a Root.FS method.
 func isValidRootFSPath(name string) bool {
        if !fs.ValidPath(name) {