all: update to use filepath.WalkDir instead of filepath.Walk

Now that filepath.WalkDir is available, it is more efficient
and should be used in place of filepath.Walk.
Update the tree to reflect best practices.

As usual, the code compiled with Go 1.4 during bootstrap is excluded.
(In this CL, that's only cmd/dist.)

For #42027.

Change-Id: Ib0f7b1e43e50b789052f9835a63ced701d8c411c
Reviewed-on: https://go-review.googlesource.com/c/go/+/267719
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

17 files changed, 65 insertions, 45 deletions

diff --git a/src/cmd/compile/fmt_test.go b/src/cmd/compile/fmt_test.go
index e372259c78..6625ccf5e2 100644
--- a/src/cmd/compile/fmt_test.go
+++ b/src/cmd/compile/fmt_test.go
@@ -52,6 +52,7 @@ import (
 	"go/types"
 	"internal/testenv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"os"
@@ -89,7 +90,7 @@ func TestFormats(t *testing.T) {
 	testenv.MustHaveGoBuild(t) // more restrictive than necessary, but that's ok
 
 	// process all directories
-	filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
+	filepath.WalkDir(".", func(path string, info fs.DirEntry, err error) error {
 		if info.IsDir() {
 			if info.Name() == "testdata" {
 				return filepath.SkipDir
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index 2a17ab9cae..955ce2a063 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -1509,6 +1509,7 @@ func (t *tester) makeGOROOTUnwritable() (undo func()) {
 	}
 	gocacheSubdir, _ := filepath.Rel(dir, gocache)
 
+	// Note: Can't use WalkDir here, because this has to compile with Go 1.4.
 	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
 		if suffix := strings.TrimPrefix(path, dir+string(filepath.Separator)); suffix != "" {
 			if suffix == gocacheSubdir {
diff --git a/src/cmd/fix/main.go b/src/cmd/fix/main.go
index 1cea9a876a..1cedf992cf 100644
--- a/src/cmd/fix/main.go
+++ b/src/cmd/fix/main.go
@@ -234,10 +234,10 @@ func report(err error) {
 }
 
 func walkDir(path string) {
-	filepath.Walk(path, visitFile)
+	filepath.WalkDir(path, visitFile)
 }
 
-func visitFile(path string, f fs.FileInfo, err error) error {
+func visitFile(path string, f fs.DirEntry, err error) error {
 	if err == nil && isGoFile(f) {
 		err = processFile(path, false)
 	}
@@ -247,7 +247,7 @@ func visitFile(path string, f fs.FileInfo, err error) error {
 	return nil
 }
 
-func isGoFile(f fs.FileInfo) bool {
+func isGoFile(f fs.DirEntry) bool {
 	// ignore non-Go files
 	name := f.Name()
 	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index a02231fa98..a730c87f97 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -774,7 +774,7 @@ func (tg *testgoData) cleanup() {
 func removeAll(dir string) error {
 	// module cache has 0444 directories;
 	// make them writable in order to remove content.
-	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
+	filepath.WalkDir(dir, func(path string, info fs.DirEntry, err error) error {
 		// chmod not only directories, but also things that we couldn't even stat
 		// due to permission errors: they may also be unreadable directories.
 		if err != nil || info.IsDir() {
@@ -820,8 +820,8 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
 	} {
 		srcdir := filepath.Join(testGOROOT, copydir)
 		tg.tempDir(filepath.Join("goroot", copydir))
-		err := filepath.Walk(srcdir,
-			func(path string, info fs.FileInfo, err error) error {
+		err := filepath.WalkDir(srcdir,
+			func(path string, info fs.DirEntry, err error) error {
 				if err != nil {
 					return err
 				}
@@ -838,9 +838,6 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
 					return err
 				}
 				tg.tempFile(dest, string(data))
-				if err := os.Chmod(tg.path(dest), info.Mode()|0200); err != nil {
-					return err
-				}
 				return nil
 			})
 		if err != nil {
diff --git a/src/cmd/go/internal/modfetch/fetch.go b/src/cmd/go/internal/modfetch/fetch.go
index a3e2cd1f9d..2ee78de5b2 100644
--- a/src/cmd/go/internal/modfetch/fetch.go
+++ b/src/cmd/go/internal/modfetch/fetch.go
@@ -318,9 +318,10 @@ func makeDirsReadOnly(dir string) {
 		mode fs.FileMode
 	}
 	var dirs []pathMode // in lexical order
-	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
-		if err == nil && info.Mode()&0222 != 0 {
-			if info.IsDir() {
+	filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
+		if err == nil && d.IsDir() {
+			info, err := d.Info()
+			if err == nil && info.Mode()&0222 != 0 {
 				dirs = append(dirs, pathMode{path, info.Mode()})
 			}
 		}
@@ -337,7 +338,7 @@ func makeDirsReadOnly(dir string) {
 // any permission changes needed to do so.
 func RemoveAll(dir string) error {
 	// Module cache has 0555 directories; make them writable in order to remove content.
-	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
+	filepath.WalkDir(dir, func(path string, info fs.DirEntry, err error) error {
 		if err != nil {
 			return nil // ignore errors walking in file system
 		}
diff --git a/src/cmd/go/internal/version/version.go b/src/cmd/go/internal/version/version.go
index 44ac24c62d..58cbd32e78 100644
--- a/src/cmd/go/internal/version/version.go
+++ b/src/cmd/go/internal/version/version.go
@@ -88,8 +88,15 @@ func runVersion(ctx context.Context, cmd *base.Command, args []string) {
 
 // scanDir scans a directory for executables to run scanFile on.
 func scanDir(dir string) {
-	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
-		if info.Mode().IsRegular() || info.Mode()&fs.ModeSymlink != 0 {
+	filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
+		if d.Type().IsRegular() || d.Type()&fs.ModeSymlink != 0 {
+			info, err := d.Info()
+			if err != nil {
+				if *versionV {
+					fmt.Fprintf(os.Stderr, "%s: %v\n", path, err)
+				}
+				return nil
+			}
 			scanFile(path, info, *versionV)
 		}
 		return nil
@@ -120,6 +127,7 @@ func scanFile(file string, info fs.FileInfo, mustPrint bool) {
 		}
 		info = i
 	}
+
 	if !isExe(file, info) {
 		if mustPrint {
 			fmt.Fprintf(os.Stderr, "%s: not executable file\n", file)
diff --git a/src/cmd/go/testdata/addmod.go b/src/cmd/go/testdata/addmod.go
index d1b6467c5d..71ac47fdc1 100644
--- a/src/cmd/go/testdata/addmod.go
+++ b/src/cmd/go/testdata/addmod.go
@@ -122,8 +122,8 @@ func main() {
 			{Name: ".info", Data: info},
 		}
 		dir = filepath.Clean(dir)
-		err = filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
-			if !info.Mode().IsRegular() {
+		err = filepath.WalkDir(dir, func(path string, info fs.DirEntry, err error) error {
+			if !info.Type().IsRegular() {
 				return nil
 			}
 			name := info.Name()
diff --git a/src/cmd/go/testdata/savedir.go b/src/cmd/go/testdata/savedir.go
index 04902df61e..75895ee279 100644
--- a/src/cmd/go/testdata/savedir.go
+++ b/src/cmd/go/testdata/savedir.go
@@ -49,7 +49,7 @@ func main() {
 
 	a := new(txtar.Archive)
 	dir = filepath.Clean(dir)
-	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
+	filepath.WalkDir(dir, func(path string, info fs.DirEntry, err error) error {
 		if path == dir {
 			return nil
 		}
@@ -60,7 +60,7 @@ func main() {
 			}
 			return nil
 		}
-		if !info.Mode().IsRegular() {
+		if !info.Type().IsRegular() {
 			return nil
 		}
 		data, err := ioutil.ReadFile(path)
diff --git a/src/cmd/gofmt/gofmt.go b/src/cmd/gofmt/gofmt.go
index dba2411eed..719c681a3e 100644
--- a/src/cmd/gofmt/gofmt.go
+++ b/src/cmd/gofmt/gofmt.go
@@ -74,7 +74,7 @@ func initParserMode() {
 	}
 }
 
-func isGoFile(f fs.FileInfo) bool {
+func isGoFile(f fs.DirEntry) bool {
 	// ignore non-Go files
 	name := f.Name()
 	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
@@ -164,7 +164,7 @@ func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error
 	return err
 }
 
-func visitFile(path string, f fs.FileInfo, err error) error {
+func visitFile(path string, f fs.DirEntry, err error) error {
 	if err == nil && isGoFile(f) {
 		err = processFile(path, nil, os.Stdout, false)
 	}
@@ -177,7 +177,7 @@ func visitFile(path string, f fs.FileInfo, err error) error {
 }
 
 func walkDir(path string) {
-	filepath.Walk(path, visitFile)
+	filepath.WalkDir(path, visitFile)
 }
 
 func main() {
diff --git a/src/cmd/gofmt/long_test.go b/src/cmd/gofmt/long_test.go
index 28306ce83e..4a821705f1 100644
--- a/src/cmd/gofmt/long_test.go
+++ b/src/cmd/gofmt/long_test.go
@@ -108,12 +108,12 @@ func testFiles(t *testing.T, filenames <-chan string, done chan<- int) {
 func genFilenames(t *testing.T, filenames chan<- string) {
 	defer close(filenames)
 
-	handleFile := func(filename string, fi fs.FileInfo, err error) error {
+	handleFile := func(filename string, d fs.DirEntry, err error) error {
 		if err != nil {
 			t.Error(err)
 			return nil
 		}
-		if isGoFile(fi) {
+		if isGoFile(d) {
 			filenames <- filename
 			nfiles++
 		}
@@ -124,13 +124,13 @@ func genFilenames(t *testing.T, filenames chan<- string) {
 	if *files != "" {
 		for _, filename := range strings.Split(*files, ",") {
 			fi, err := os.Stat(filename)
-			handleFile(filename, fi, err)
+			handleFile(filename, &statDirEntry{fi}, err)
 		}
 		return // ignore files under -root
 	}
 
 	// otherwise, test all Go files under *root
-	filepath.Walk(*root, handleFile)
+	filepath.WalkDir(*root, handleFile)
 }
 
 func TestAll(t *testing.T) {
@@ -164,3 +164,12 @@ func TestAll(t *testing.T) {
 		fmt.Printf("processed %d files\n", nfiles)
 	}
 }
+
+type statDirEntry struct {
+	info fs.FileInfo
+}
+
+func (d *statDirEntry) Name() string               { return d.info.Name() }
+func (d *statDirEntry) IsDir() bool                { return d.info.IsDir() }
+func (d *statDirEntry) Type() fs.FileMode          { return d.info.Mode().Type() }
+func (d *statDirEntry) Info() (fs.FileInfo, error) { return d.info, nil }
diff --git a/src/cmd/internal/moddeps/moddeps_test.go b/src/cmd/internal/moddeps/moddeps_test.go
index 7362e7868b..9ea21873c5 100644
--- a/src/cmd/internal/moddeps/moddeps_test.go
+++ b/src/cmd/internal/moddeps/moddeps_test.go
@@ -33,7 +33,7 @@ func findGorootModules(t *testing.T) []gorootModule {
 	goBin := testenv.GoToolPath(t)
 
 	goroot.once.Do(func() {
-		goroot.err = filepath.Walk(runtime.GOROOT(), func(path string, info fs.FileInfo, err error) error {
+		goroot.err = filepath.WalkDir(runtime.GOROOT(), func(path string, info fs.DirEntry, err error) error {
 			if err != nil {
 				return err
 			}
diff --git a/src/compress/gzip/issue14937_test.go b/src/compress/gzip/issue14937_test.go
index 24db3641aa..20da0b6824 100644
--- a/src/compress/gzip/issue14937_test.go
+++ b/src/compress/gzip/issue14937_test.go
@@ -31,7 +31,7 @@ func TestGZIPFilesHaveZeroMTimes(t *testing.T) {
 		t.Fatal("error evaluating GOROOT: ", err)
 	}
 	var files []string
-	err = filepath.Walk(goroot, func(path string, info fs.FileInfo, err error) error {
+	err = filepath.WalkDir(goroot, func(path string, info fs.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index bf1367355d..e9ed26aa5f 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -510,8 +510,8 @@ func listStdPkgs(goroot string) ([]string, error) {
 	var pkgs []string
 
 	src := filepath.Join(goroot, "src") + string(filepath.Separator)
-	walkFn := func(path string, fi fs.FileInfo, err error) error {
-		if err != nil || !fi.IsDir() || path == src {
+	walkFn := func(path string, d fs.DirEntry, err error) error {
+		if err != nil || !d.IsDir() || path == src {
 			return nil
 		}
 
@@ -528,7 +528,7 @@ func listStdPkgs(goroot string) ([]string, error) {
 		pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
 		return nil
 	}
-	if err := filepath.Walk(src, walkFn); err != nil {
+	if err := filepath.WalkDir(src, walkFn); err != nil {
 		return nil, err
 	}
 	return pkgs, nil
diff --git a/src/go/doc/headscan.go b/src/go/doc/headscan.go
index 8ea462366e..fe26a0ea84 100644
--- a/src/go/doc/headscan.go
+++ b/src/go/doc/headscan.go
@@ -69,8 +69,8 @@ func main() {
 	flag.Parse()
 	fset := token.NewFileSet()
 	nheadings := 0
-	err := filepath.Walk(*root, func(path string, fi fs.FileInfo, err error) error {
-		if !fi.IsDir() {
+	err := filepath.WalkDir(*root, func(path string, info fs.DirEntry, err error) error {
+		if !info.IsDir() {
 			return nil
 		}
 		pkgs, err := parser.ParseDir(fset, path, isGoFile, parser.ParseComments)
diff --git a/src/index/suffixarray/suffixarray_test.go b/src/index/suffixarray/suffixarray_test.go
index b6a81123b7..a11a98dae0 100644
--- a/src/index/suffixarray/suffixarray_test.go
+++ b/src/index/suffixarray/suffixarray_test.go
@@ -503,7 +503,7 @@ func makeText(name string) ([]byte, error) {
 			return nil, err
 		}
 	case "go":
-		err := filepath.Walk("../..", func(path string, info fs.FileInfo, err error) error {
+		err := filepath.WalkDir("../..", func(path string, info fs.DirEntry, err error) error {
 			if err == nil && strings.HasSuffix(path, ".go") && !info.IsDir() {
 				file, err := ioutil.ReadFile(path)
 				if err != nil {
diff --git a/test/run.go b/test/run.go
index 672861c8d7..4abf32d25c 100644
--- a/test/run.go
+++ b/test/run.go
@@ -14,6 +14,7 @@ import (
 	"fmt"
 	"hash/fnv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"os"
@@ -1793,7 +1794,7 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
+	return filepath.WalkDir(srcRoot, func(srcPath string, d fs.DirEntry, err error) error {
 		if err != nil || srcPath == srcRoot {
 			return err
 		}
@@ -1804,14 +1805,16 @@ func overlayDir(dstRoot, srcRoot string) error {
 		}
 		dstPath := filepath.Join(dstRoot, suffix)
 
-		perm := info.Mode() & os.ModePerm
-		if info.Mode()&os.ModeSymlink != 0 {
+		var info fs.FileInfo
+		if d.Type()&os.ModeSymlink != 0 {
 			info, err = os.Stat(srcPath)
-			if err != nil {
-				return err
-			}
-			perm = info.Mode() & os.ModePerm
+		} else {
+			info, err = d.Info()
 		}
+		if err != nil {
+			return err
+		}
+		perm := info.Mode() & os.ModePerm
 
 		// Always copy directories (don't symlink them).
 		// If we add a file in the overlay, we don't want to add it in the original.
diff --git a/test/winbatch.go b/test/winbatch.go
index c3b48d385c..54c2fff134 100644
--- a/test/winbatch.go
+++ b/test/winbatch.go
@@ -27,11 +27,11 @@ func main() {
 	// Walk the entire Go repository source tree (without GOROOT/pkg),
 	// skipping directories that start with "." and named "testdata",
 	// and ensure all .bat files found have exact CRLF line endings.
-	err := filepath.Walk(runtime.GOROOT(), func(path string, fi os.FileInfo, err error) error {
+	err := filepath.WalkDir(runtime.GOROOT(), func(path string, d os.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
-		if fi.IsDir() && (strings.HasPrefix(fi.Name(), ".") || fi.Name() == "testdata") {
+		if d.IsDir() && (strings.HasPrefix(d.Name(), ".") || d.Name() == "testdata") {
 			return filepath.SkipDir
 		}
 		if path == filepath.Join(runtime.GOROOT(), "pkg") {
@@ -39,7 +39,7 @@ func main() {
 			// Skip it to avoid false positives. (Also see golang.org/issue/37929.)
 			return filepath.SkipDir
 		}
-		if filepath.Ext(fi.Name()) == ".bat" {
+		if filepath.Ext(d.Name()) == ".bat" {
 			enforceBatchStrictCRLF(path)
 		}
 		return nil