path/filepath: revert "add WalkDir"

This reverts CL 266240.

Reason for revert: tests aren't passing on windows-amd64-longtest.

Change-Id: If323c6254a42aff0418e2c0a9531f3d4c829a242
Reviewed-on: https://go-review.googlesource.com/c/go/+/267798
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

3 files changed, 54 insertions, 250 deletions

diff --git a/src/path/filepath/export_test.go b/src/path/filepath/export_test.go
index e7ad7dd01a..0cf9e3bca1 100644
--- a/src/path/filepath/export_test.go
+++ b/src/path/filepath/export_test.go
@@ -5,5 +5,3 @@
 package filepath
 
 var LstatP = &lstat
-
-type DirEntryFromInfo = dirEntryFromInfo
diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go
index 3f7e5c713d..dffd27db14 100644
--- a/src/path/filepath/path.go
+++ b/src/path/filepath/path.go
@@ -336,130 +336,25 @@ func Rel(basepath, targpath string) (string, error) {
 // as an error by any function.
 var SkipDir = errors.New("skip this directory")
 
-// WalkDirFunc is the type of the function called by WalkDir to visit
-// each each file or directory.
-//
-// The path argument contains the argument to Walk as a prefix.
-// That is, if Walk is called with root argument "dir" and finds a file
-// named "a" in that directory, the walk function will be called with
-// argument "dir/a".
-//
-// The directory and file are joined with Join, which may clean the
-// directory name: if Walk is called with the root argument "x/../dir"
-// and finds a file named "a" in that directory, the walk function will
-// be called with argument "dir/a", not "x/../dir/a".
-//
-// The d argument is the fs.DirEntry for the named path.
-//
-// The error result returned by the function controls how WalkDir
-// continues. If the function returns the special value SkipDir, WalkDir
-// skips the current directory (path if d.IsDir() is true, otherwise
-// path's parent directory). Otherwise, if the function returns a non-nil
-// error, WalkDir stops entirely and returns that error.
-//
-// The err argument reports an error related to path, signaling that
-// WalkDir will not walk into that directory. The function can decide how
-// to handle that error; as described earlier, returning the error will
-// cause WalkDir to stop walking the entire tree.
-//
-// WalkDir calls the function with a non-nil err argument in two cases.
-//
-// First, if the initial os.Lstat on the root directory fails, WalkDir
-// calls the function with path set to root, d set to nil, and err set to
-// the error from os.Lstat.
-//
-// Second, if a directory's ReadDir method fails, WalkDir calls the
-// function with path set to the directory's path, d set to an
-// fs.DirEntry describing the directory, and err set to the error from
-// ReadDir. In this second case, the function is called twice with the
-// path of the directory: the first call is before the directory read is
-// attempted and has err set to nil, giving the function a chance to
-// return SkipDir and avoid the ReadDir entirely. The second call is
-// after a failed ReadDir and reports the error from ReadDir.
-// (If ReadDir succeeds, there is no second call.)
-//
-// The differences between WalkDirFunc compared to WalkFunc are:
-//
-//   - The second argument has type fs.DirEntry instead of fs.FileInfo.
-//   - The function is called before reading a directory, to allow SkipDir
-//     to bypass the directory read entirely.
-//   - If a directory read fails, the function is called a second time
-//     for that directory to report the error.
-//
-type WalkDirFunc func(path string, d fs.DirEntry, err error) error
-
-// WalkFunc is the type of the function called by Walk to visit each each
-// file or directory.
-//
-// The path argument contains the argument to Walk as a prefix.
-// That is, if Walk is called with root argument "dir" and finds a file
-// named "a" in that directory, the walk function will be called with
-// argument "dir/a".
-//
-// The directory and file are joined with Join, which may clean the
-// directory name: if Walk is called with the root argument "x/../dir"
-// and finds a file named "a" in that directory, the walk function will
-// be called with argument "dir/a", not "x/../dir/a".
-//
-// The info argument is the fs.FileInfo for the named path.
-//
-// The error result returned by the function controls how Walk continues.
-// If the function returns the special value SkipDir, Walk skips the
-// current directory (path if info.IsDir() is true, otherwise path's
-// parent directory). Otherwise, if the function returns a non-nil error,
-// Walk stops entirely and returns that error.
-//
-// The err argument reports an error related to path, signaling that Walk
-// will not walk into that directory. The function can decide how to
-// handle that error; as described earlier, returning the error will
-// cause Walk to stop walking the entire tree.
-//
-// Walk calls the function with a non-nil err argument in two cases.
-//
-// First, if an os.Lstat on the root directory or any directory or file
-// in the tree fails, Walk calls the function with path set to that
-// directory or file's path, info set to nil, and err set to the error
-// from os.Lstat.
-//
-// Second, if a directory's Readdirnames method fails, Walk calls the
-// function with path set to the directory's path, info, set to an
-// fs.FileInfo describing the directory, and err set to the error from
-// Readdirnames.
+// WalkFunc is the type of the function called for each file or directory
+// visited by Walk. The path argument contains the argument to Walk as a
+// prefix; that is, if Walk is called with "dir", which is a directory
+// containing the file "a", the walk function will be called with argument
+// "dir/a". The info argument is the fs.FileInfo for the named path.
+//
+// If there was a problem walking to the file or directory named by path, the
+// incoming error will describe the problem and the function can decide how
+// to handle that error (and Walk will not descend into that directory). In the
+// case of an error, the info argument will be nil. If an error is returned,
+// processing stops. The sole exception is when the function returns the special
+// value SkipDir. If the function returns SkipDir when invoked on a directory,
+// Walk skips the directory's contents entirely. If the function returns SkipDir
+// when invoked on a non-directory file, Walk skips the remaining files in the
+// containing directory.
 type WalkFunc func(path string, info fs.FileInfo, err error) error
 
 var lstat = os.Lstat // for testing
 
-// walkDir recursively descends path, calling walkDirFn.
-func walkDir(path string, d fs.DirEntry, walkDirFn WalkDirFunc) error {
-	if err := walkDirFn(path, d, nil); err != nil || !d.IsDir() {
-		if err == SkipDir && d.IsDir() {
-			// Successfully skipped directory.
-			err = nil
-		}
-		return err
-	}
-
-	dirs, err := readDir(path)
-	if err != nil {
-		// Second call, to report ReadDir error.
-		err = walkDirFn(path, d, err)
-		if err != nil {
-			return err
-		}
-	}
-
-	for _, d1 := range dirs {
-		path1 := Join(path, d1.Name())
-		if err := walkDir(path1, d1, walkDirFn); err != nil {
-			if err == SkipDir {
-				break
-			}
-			return err
-		}
-	}
-	return nil
-}
-
 // walk recursively descends path, calling walkFn.
 func walk(path string, info fs.FileInfo, walkFn WalkFunc) error {
 	if !info.IsDir() {
@@ -498,62 +393,18 @@ func walk(path string, info fs.FileInfo, walkFn WalkFunc) error {
 	return nil
 }
 
-// WalkDir walks the file tree rooted at root, calling fn for each file or
-// directory in the tree, including root.
-//
-// All errors that arise visiting files and directories are filtered by fn:
-// see the WalkDirFunc documentation for details.
-//
-// The files are walked in lexical order, which makes the output deterministic
-// but requires WalkDir to read an entire directory into memory before proceeding
-// to walk that directory.
-//
-// WalkDir does not follow symbolic links.
-func WalkDir(root string, fn WalkDirFunc) error {
-	info, err := os.Lstat(root)
-	if err != nil {
-		err = fn(root, nil, err)
-	} else {
-		err = walkDir(root, &dirEntryFromInfo{info}, fn)
-	}
-	if err == SkipDir {
-		return nil
-	}
-	return err
-}
-
-type dirEntryFromInfo struct {
-	fs.FileInfo
-}
-
-func (e *dirEntryFromInfo) Type() fs.FileMode {
-	return e.Mode().Type()
-}
-
-func (e *dirEntryFromInfo) Info() (fs.FileInfo, error) {
-	return e.FileInfo, nil
-}
-
-// Walk walks the file tree rooted at root, calling fn for each file or
-// directory in the tree, including root.
-//
-// All errors that arise visiting files and directories are filtered by fn:
-// see the WalkFunc documentation for details.
-//
-// The files are walked in lexical order, which makes the output deterministic
-// but requires Walk to read an entire directory into memory before proceeding
-// to walk that directory.
-//
+// Walk walks the file tree rooted at root, calling walkFn for each file or
+// directory in the tree, including root. All errors that arise visiting files
+// and directories are filtered by walkFn. The files are walked in lexical
+// order, which makes the output deterministic but means that for very
+// large directories Walk can be inefficient.
 // Walk does not follow symbolic links.
-//
-// Walk is less efficient than WalkDir, introduced in Go 1.16,
-// which avoids calling os.Lstat on every visited file or directory.
-func Walk(root string, fn WalkFunc) error {
+func Walk(root string, walkFn WalkFunc) error {
 	info, err := os.Lstat(root)
 	if err != nil {
-		err = fn(root, nil, err)
+		err = walkFn(root, nil, err)
 	} else {
-		err = walk(root, info, fn)
+		err = walk(root, info, walkFn)
 	}
 	if err == SkipDir {
 		return nil
@@ -561,24 +412,8 @@ func Walk(root string, fn WalkFunc) error {
 	return err
 }
 
-// readDir reads the directory named by dirname and returns
-// a sorted list of directory entries.
-func readDir(dirname string) ([]fs.DirEntry, error) {
-	f, err := os.Open(dirname)
-	if err != nil {
-		return nil, err
-	}
-	dirs, err := f.ReadDir(-1)
-	f.Close()
-	if err != nil {
-		return nil, err
-	}
-	sort.Slice(dirs, func(i, j int) bool { return dirs[i].Name() < dirs[j].Name() })
-	return dirs, nil
-}
-
 // readDirNames reads the directory named by dirname and returns
-// a sorted list of directory entry names.
+// a sorted list of directory entries.
 func readDirNames(dirname string) ([]string, error) {
 	f, err := os.Open(dirname)
 	if err != nil {
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
index af6b69de09..7dc8b60c28 100644
--- a/src/path/filepath/path_test.go
+++ b/src/path/filepath/path_test.go
@@ -394,8 +394,8 @@ func checkMarks(t *testing.T, report bool) {
 // Assumes that each node name is unique. Good enough for a test.
 // If clear is true, any incoming error is cleared before return. The errors
 // are always accumulated, though.
-func mark(d fs.DirEntry, err error, errors *[]error, clear bool) error {
-	name := d.Name()
+func mark(info fs.FileInfo, err error, errors *[]error, clear bool) error {
+	name := info.Name()
 	walkTree(tree, tree.name, func(path string, n *Node) {
 		if n.name == name {
 			n.mark++
@@ -432,19 +432,6 @@ func chtmpdir(t *testing.T) (restore func()) {
 }
 
 func TestWalk(t *testing.T) {
-	walk := func(root string, fn filepath.WalkDirFunc) error {
-		return filepath.Walk(root, func(path string, info fs.FileInfo, err error) error {
-			return fn(path, &filepath.DirEntryFromInfo{info}, err)
-		})
-	}
-	testWalk(t, walk, 1)
-}
-
-func TestWalkDir(t *testing.T) {
-	testWalk(t, filepath.WalkDir, 2)
-}
-
-func testWalk(t *testing.T, walk func(string, filepath.WalkDirFunc) error, errVisit int) {
 	if runtime.GOOS == "ios" {
 		restore := chtmpdir(t)
 		defer restore()
@@ -468,11 +455,11 @@ func testWalk(t *testing.T, walk func(string, filepath.WalkDirFunc) error, errVi
 	makeTree(t)
 	errors := make([]error, 0, 10)
 	clear := true
-	markFn := func(path string, d fs.DirEntry, err error) error {
-		return mark(d, err, &errors, clear)
+	markFn := func(path string, info fs.FileInfo, err error) error {
+		return mark(info, err, &errors, clear)
 	}
 	// Expect no errors.
-	err = walk(tree.name, markFn)
+	err = filepath.Walk(tree.name, markFn)
 	if err != nil {
 		t.Fatalf("no error expected, found: %s", err)
 	}
@@ -482,17 +469,10 @@ func testWalk(t *testing.T, walk func(string, filepath.WalkDirFunc) error, errVi
 	checkMarks(t, true)
 	errors = errors[0:0]
 
-	t.Run("PermErr", func(t *testing.T) {
-		// Test permission errors. Only possible if we're not root
-		// and only on some file systems (AFS, FAT).  To avoid errors during
-		// all.bash on those file systems, skip during go test -short.
-		if os.Getuid() == 0 {
-			t.Skip("skipping as root")
-		}
-		if testing.Short() {
-			t.Skip("skipping in short mode")
-		}
-
+	// Test permission errors. Only possible if we're not root
+	// and only on some file systems (AFS, FAT).  To avoid errors during
+	// all.bash on those file systems, skip during go test -short.
+	if os.Getuid() > 0 && !testing.Short() {
 		// introduce 2 errors: chmod top-level directories to 0
 		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0)
 		os.Chmod(filepath.Join(tree.name, tree.entries[3].name), 0)
@@ -502,9 +482,9 @@ func testWalk(t *testing.T, walk func(string, filepath.WalkDirFunc) error, errVi
 		markTree(tree.entries[1])
 		markTree(tree.entries[3])
 		// correct double-marking of directory itself
-		tree.entries[1].mark -= errVisit
-		tree.entries[3].mark -= errVisit
-		err := walk(tree.name, markFn)
+		tree.entries[1].mark--
+		tree.entries[3].mark--
+		err := filepath.Walk(tree.name, markFn)
 		if err != nil {
 			t.Fatalf("expected no error return from Walk, got %s", err)
 		}
@@ -520,10 +500,10 @@ func testWalk(t *testing.T, walk func(string, filepath.WalkDirFunc) error, errVi
 		markTree(tree.entries[1])
 		markTree(tree.entries[3])
 		// correct double-marking of directory itself
-		tree.entries[1].mark -= errVisit
-		tree.entries[3].mark -= errVisit
+		tree.entries[1].mark--
+		tree.entries[3].mark--
 		clear = false // error will stop processing
-		err = walk(tree.name, markFn)
+		err = filepath.Walk(tree.name, markFn)
 		if err == nil {
 			t.Fatalf("expected error return from Walk")
 		}
@@ -537,7 +517,7 @@ func testWalk(t *testing.T, walk func(string, filepath.WalkDirFunc) error, errVi
 		// restore permissions
 		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0770)
 		os.Chmod(filepath.Join(tree.name, tree.entries[3].name), 0770)
-	})
+	}
 }
 
 func touch(t *testing.T, name string) {
@@ -564,7 +544,7 @@ func TestWalkSkipDirOnFile(t *testing.T) {
 	touch(t, filepath.Join(td, "dir/foo2"))
 
 	sawFoo2 := false
-	walker := func(path string) error {
+	walker := func(path string, info fs.FileInfo, err error) error {
 		if strings.HasSuffix(path, "foo2") {
 			sawFoo2 = true
 		}
@@ -573,31 +553,22 @@ func TestWalkSkipDirOnFile(t *testing.T) {
 		}
 		return nil
 	}
-	walkFn := func(path string, _ fs.FileInfo, _ error) error { return walker(path) }
-	walkDirFn := func(path string, _ fs.DirEntry, _ error) error { return walker(path) }
 
-	check := func(t *testing.T, walk func(root string) error, root string) {
-		t.Helper()
-		sawFoo2 = false
-		err = walk(root)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if sawFoo2 {
-			t.Errorf("SkipDir on file foo1 did not block processing of foo2")
-		}
+	err = filepath.Walk(td, walker)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sawFoo2 {
+		t.Errorf("SkipDir on file foo1 did not block processing of foo2")
 	}
 
-	t.Run("Walk", func(t *testing.T) {
-		Walk := func(root string) error { return filepath.Walk(td, walkFn) }
-		check(t, Walk, td)
-		check(t, Walk, filepath.Join(td, "dir"))
-	})
-	t.Run("WalkDir", func(t *testing.T) {
-		WalkDir := func(root string) error { return filepath.WalkDir(td, walkDirFn) }
-		check(t, WalkDir, td)
-		check(t, WalkDir, filepath.Join(td, "dir"))
-	})
+	err = filepath.Walk(filepath.Join(td, "dir"), walker)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sawFoo2 {
+		t.Errorf("SkipDir on file foo1 did not block processing of foo2")
+	}
 }
 
 func TestWalkFileError(t *testing.T) {