Add comments and refactor

go/runfiles/fs.go

@@ -55,7 +55,7 @@ func (r *Runfiles) Open(name string) (fs.File, error) {
 		return f, nil
 	}
 	// Return a special file for a repo dir that knows its apparent name.
-	return &repoDir{f.(fs.ReadDirFile), split[0]}, nil
+	return &repoDirFile{f.(fs.ReadDirFile), split[0]}, nil
 }
 
 type rootDir struct {
@@ -107,7 +107,7 @@ func (r *rootDir) initEntries() error {
 		if apparent, ok := canonicalToApparentName[e.Name()]; ok && e.IsDir() {
 			// A repo directory that is visible to the current source repo is materialized
 			// under its apparent name.
-			r.entries = append(r.entries, repoDirEntry{apparent, r.rf})
+			r.entries = append(r.entries, repoDirEntry{e, apparent})
 		} else if _, ok := allCanonicalNames[e.Name()]; ok && e.IsDir() {
 			// Skip repo directory that isn't visible to the current source repo.
 		} else {
@@ -123,35 +123,39 @@ func (r *rootDir) initEntries() error {
 	return nil
 }
 
-type repoDir struct {
+type repoDirFile struct {
 	fs.ReadDirFile
 	name string
 }
 
-func (r repoDir) Stat() (fs.FileInfo, error) {
+func (r repoDirFile) Stat() (fs.FileInfo, error) {
 	info, err := r.ReadDirFile.Stat()
 	if err != nil {
 		return nil, err
 	}
 	return repoDirFileInfo{info, r.name}, nil
 }
 
-type repoDirFileInfo struct {
-	fs.FileInfo
+type repoDirEntry struct {
+	fs.DirEntry
 	name string
 }
 
-func (r repoDirFileInfo) Name() string { return r.name }
+func (r repoDirEntry) Name() string { return r.name }
+func (r repoDirEntry) Info() (fs.FileInfo, error) {
+	info, err := r.DirEntry.Info()
+	if err != nil {
+		return nil, err
+	}
+	return repoDirFileInfo{info, r.name}, nil
+}
 
-type repoDirEntry struct {
+type repoDirFileInfo struct {
+	fs.FileInfo
 	name string
-	rf   *Runfiles
 }
 
-func (r repoDirEntry) Name() string { return r.name }
-func (r repoDirEntry) IsDir() bool { return true }
-func (r repoDirEntry) Type() fs.FileMode { return fs.ModeDir }
-func (r repoDirEntry) Info() (fs.FileInfo, error) { return fs.Stat(r.rf, r.name) }
+func (r repoDirFileInfo) Name() string { return r.name }
 
 type emptyFile string
 

go/runfiles/manifest.go

@@ -125,6 +125,9 @@ func (m *manifest) open(name string) (fs.File, error) {
 		}
 	}
 
+	// At this point the file is not directly listed in the manifest (or
+	// contained in a directory that is). We lazily build a trie to allow
+	// efficient listing of the contents of intermediate directories.
 	m.initTrie()
 
 	dir := m.trie
@@ -187,12 +190,16 @@ func (m *manifestReadDirFile) ReadDir(n int) ([]fs.DirEntry, error) {
 	}
 	entries := m.entries[:n]
 	m.entries = m.entries[n:]
+
 	var dirEntries []fs.DirEntry
 	for _, e := range entries {
 		var info fs.FileInfo
 		if e.path == "" {
+			// The entry corresponds to a directory that is a prefix of some
+			// manifest entry. We represent it as a read-only directory.
 			info = dirFileInfo(e.name)
 		} else {
+			// The entry corresponds to a real file in the manifest.
 			var err error
 			info, err = os.Stat(e.path)
 			if err != nil {

go/runfiles/runfiles.go

@@ -77,6 +77,11 @@ const noSourceRepoSentinel = "_not_a_valid_repository_name"
 //
 // See section “Runfiles discovery” in
 // https://docs.google.com/document/d/e/2PACX-1vSDIrFnFvEYhKsCMdGdD40wZRBX3m3aZ5HhVj4CtHPmiXKDCxioTUbYsDydjKtFDAzER5eg7OjJWs3V/pub.
+//
+// The returned object implements fs.FS regardless of the type of runfiles
+// that backs it. This is the preferred way to interact with runfiles in a
+// platform-agnostic way. For example, to find all runfiles beneath a
+// directory, use fs.Glob.
 func New(opts ...Option) (*Runfiles, error) {
 	var o options
 	o.sourceRepo = noSourceRepoSentinel

tests/runfiles/testfs/testfs.go

@@ -1,10 +1,14 @@
+// Taken from
+// https://github.com/golang/go/blob/e8ee1dc4f9e2632ba1018610d1a1187743ae397f/src/testing/fstest/testfs.go
+//
+// Modifications:
+// - fixed https://github.com/golang/go/issues/50401 by statting a dir entry to determine whether it
+//   is a symlink that resolves to a directory
+//
 // Copyright 2020 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.
 
-//go:build go1.16
-// +build go1.16
-
 package testfs
 
 import (