path/filepath: Simplify Walk interface

The last argument of filepath.Walk was removed, and the Visitor
interface now contains an Error method that is called on errors.

Fixes #2237.

R=golang-dev, gri, r
CC=golang-dev
https://golang.org/cl/4964067

src/cmd/gofix/main.go

@@ -200,7 +200,7 @@ func report(err os.Error) {
 func walkDir(path string) {
 	v := make(fileVisitor)
 	go func() {
-		filepath.Walk(path, v, v)
+		filepath.Walk(path, v)
 		close(v)
 	}()
 	for err := range v {
@@ -225,6 +225,10 @@ func (v fileVisitor) VisitFile(path string, f *os.FileInfo) {
 	}
 }
 
+func (v fileVisitor) Error(path string, err os.Error) {
+	v <- err
+}
+
 func isGoFile(f *os.FileInfo) bool {
 	// ignore non-Go files
 	return f.IsRegular() && !strings.HasPrefix(f.Name, ".") && strings.HasSuffix(f.Name, ".go")

src/cmd/gofmt/gofmt.go

@@ -164,10 +164,14 @@ func (v fileVisitor) VisitFile(path string, f *os.FileInfo) {
 	}
 }
 
+func (v fileVisitor) Error(path string, err os.Error) {
+	v <- err
+}
+
 func walkDir(path string) {
 	v := make(fileVisitor)
 	go func() {
-		filepath.Walk(path, v, v)
+		filepath.Walk(path, v)
 		close(v)
 	}()
 	for err := range v {

src/cmd/govet/govet.go

@@ -104,30 +104,34 @@ func doFile(name string, reader io.Reader) {
 // Visitor for filepath.Walk - trivial.  Just calls doFile on each file.
 // TODO: if govet becomes richer, might want to process
 // a directory (package) at a time.
-type V struct{}
+type fileVisitor chan os.Error
 
-func (v V) VisitDir(path string, f *os.FileInfo) bool {
+func (v fileVisitor) VisitDir(path string, f *os.FileInfo) bool {
 	return true
 }
 
-func (v V) VisitFile(path string, f *os.FileInfo) {
+func (v fileVisitor) VisitFile(path string, f *os.FileInfo) {
 	if strings.HasSuffix(path, ".go") {
 		doFile(path, nil)
 	}
 }
 
+func (v fileVisitor) Error(path string, err os.Error) {
+	v <- err
+}
+
 // walkDir recursively walks the tree looking for .go files.
 func walkDir(root string) {
-	errors := make(chan os.Error)
+	v := make(fileVisitor)
 	done := make(chan bool)
 	go func() {
-		for e := range errors {
+		for e := range v {
 			errorf("walk error: %s", e)
 		}
 		done <- true
 	}()
-	filepath.Walk(root, V{}, errors)
-	close(errors)
+	filepath.Walk(root, v)
+	close(v)
 	<-done
 }
 

src/pkg/path/filepath/path.go

@@ -255,14 +255,14 @@ func Abs(path string) (string, os.Error) {
 }
 
 // Visitor methods are invoked for corresponding file tree entries
-// visited by Walk. The parameter path is the full path of f relative
-// to root.
+// visited by Walk.
 type Visitor interface {
 	VisitDir(path string, f *os.FileInfo) bool
 	VisitFile(path string, f *os.FileInfo)
+	Error(path string, err os.Error)
 }
 
-func walk(path string, f *os.FileInfo, v Visitor, errors chan<- os.Error) {
+func walk(path string, f *os.FileInfo, v Visitor) {
 	if !f.IsDirectory() {
 		v.VisitFile(path, f)
 		return
@@ -274,13 +274,11 @@ func walk(path string, f *os.FileInfo, v Visitor, errors chan<- os.Error) {
 
 	list, err := readDir(path)
 	if err != nil {
-		if errors != nil {
-			errors <- err
-		}
+		v.Error(path, err)
 	}
 
 	for _, e := range list {
-		walk(Join(path, e.Name), e, v, errors)
+		walk(Join(path, e.Name), e, v)
 	}
 }
 
@@ -316,18 +314,14 @@ func (f fileInfoList) Swap(i, j int)      { f[i], f[j] = f[j], f[i] }
 // v.VisitFile for each directory or file in the tree, including root.
 // If v.VisitDir returns false, Walk skips the directory's entries;
 // otherwise it invokes itself for each directory entry in sorted order.
-// An error reading a directory does not abort the Walk.
-// If errors != nil, Walk sends each directory read error
-// to the channel.  Otherwise Walk discards the error.
-func Walk(root string, v Visitor, errors chan<- os.Error) {
+// Walk calls v.Error if an error happens while reading a directory.
+func Walk(root string, v Visitor) {
 	f, err := os.Lstat(root)
 	if err != nil {
-		if errors != nil {
-			errors <- err
-		}
+		v.Error(root, err)
 		return // can't progress
 	}
-	walk(root, f, v, errors)
+	walk(root, f, v)
 }
 
 // Base returns the last element of path.

src/pkg/path/filepath/path_test.go

@@ -299,30 +299,30 @@ func mark(name string) {
 	})
 }
 
-type TestVisitor struct{}
+type TestVisitor chan os.Error
 
-func (v *TestVisitor) VisitDir(path string, f *os.FileInfo) bool {
+func (v TestVisitor) VisitDir(path string, f *os.FileInfo) bool {
 	mark(f.Name)
 	return true
 }
 
-func (v *TestVisitor) VisitFile(path string, f *os.FileInfo) {
+func (v TestVisitor) VisitFile(path string, f *os.FileInfo) {
 	mark(f.Name)
 }
 
+func (v TestVisitor) Error(path string, err os.Error) {
+	v <- err
+}
+
 func TestWalk(t *testing.T) {
 	makeTree(t)
 
-	// 1) ignore error handling, expect none
-	v := &TestVisitor{}
-	filepath.Walk(tree.name, v, nil)
-	checkMarks(t)
+	v := make(TestVisitor, 64)
 
-	// 2) handle errors, expect none
-	errors := make(chan os.Error, 64)
-	filepath.Walk(tree.name, v, errors)
+	// 1) no errors expected.
+	filepath.Walk(tree.name, v)
 	select {
-	case err := <-errors:
+	case err := <-v:
 		t.Errorf("no error expected, found: %s", err)
 	default:
 		// ok
@@ -343,14 +343,13 @@ func TestWalk(t *testing.T) {
 		tree.entries[1].mark--
 		tree.entries[3].mark--
 
-		// 3) handle errors, expect two
-		errors = make(chan os.Error, 64)
+		// 2) expect two errors
 		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0)
-		filepath.Walk(tree.name, v, errors)
+		filepath.Walk(tree.name, v)
 	Loop:
 		for i := 1; i <= 2; i++ {
 			select {
-			case <-errors:
+			case <-v:
 				// ok
 			default:
 				t.Errorf("%d. error expected, none found", i)
@@ -358,7 +357,7 @@ func TestWalk(t *testing.T) {
 			}
 		}
 		select {
-		case err := <-errors:
+		case err := <-v:
 			t.Errorf("only two errors expected, found 3rd: %v", err)
 		default:
 			// ok