os: make MkdirAll work with symlinks

Fixes #1149.

R=adg
CC=golang-dev
https://golang.org/cl/3564041

src/pkg/os/os_test.go

@@ -863,13 +863,14 @@ func TestAppend(t *testing.T) {
 }
 
 func TestStatDirWithTrailingSlash(t *testing.T) {
-	// Create new dir, in _obj so it will get
+	// Create new dir, in _test so it will get
 	// cleaned up by make if not by us.
-	path := "_obj/_TestStatDirWithSlash_"
+	path := "_test/_TestStatDirWithSlash_"
 	err := MkdirAll(path, 0777)
 	if err != nil {
 		t.Fatalf("MkdirAll %q: %s", path, err)
 	}
+	defer RemoveAll(path)
 
 	// Stat of path should succeed.
 	_, err = Stat(path)
@@ -882,6 +883,4 @@ func TestStatDirWithTrailingSlash(t *testing.T) {
 	if err != nil {
 		t.Fatal("stat failed:", err)
 	}
-
-	RemoveAll("_obj/_TestMkdirAll_")
 }

src/pkg/os/path.go

@@ -14,7 +14,7 @@ package os
 // and returns nil.
 func MkdirAll(path string, perm uint32) Error {
 	// If path exists, stop with success or error.
-	dir, err := Lstat(path)
+	dir, err := Stat(path)
 	if err == nil {
 		if dir.IsDirectory() {
 			return nil

src/pkg/os/path_test.go

@@ -7,17 +7,19 @@ package os_test
 import (
 	. "os"
 	"testing"
+	"runtime"
 	"syscall"
 )
 
 func TestMkdirAll(t *testing.T) {
-	// Create new dir, in _obj so it will get
+	// Create new dir, in _test so it will get
 	// cleaned up by make if not by us.
-	path := "_obj/_TestMkdirAll_/dir/./dir2"
+	path := "_test/_TestMkdirAll_/dir/./dir2"
 	err := MkdirAll(path, 0777)
 	if err != nil {
 		t.Fatalf("MkdirAll %q: %s", path, err)
 	}
+	defer RemoveAll("_test/_TestMkdirAll_")
 
 	// Already exists, should succeed.
 	err = MkdirAll(path, 0777)
@@ -58,13 +60,11 @@ func TestMkdirAll(t *testing.T) {
 	if perr.Path != fpath {
 		t.Fatalf("MkdirAll %q returned wrong error path: %q not %q", ffpath, perr.Path, fpath)
 	}
-
-	RemoveAll("_obj/_TestMkdirAll_")
 }
 
 func TestRemoveAll(t *testing.T) {
 	// Work directory.
-	path := "_obj/_TestRemoveAll_"
+	path := "_test/_TestRemoveAll_"
 	fpath := path + "/file"
 	dpath := path + "/dir"
 
@@ -154,3 +154,28 @@ func TestRemoveAll(t *testing.T) {
 		t.Fatalf("Lstat %q succeeded after RemoveAll (final)", path)
 	}
 }
+
+func TestMkdirAllWithSymlink(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Log("Skipping test: symlinks don't exist under Windows")
+		return
+	}
+
+	err := Mkdir("_test/dir", 0755)
+	if err != nil {
+		t.Fatal(`Mkdir "_test/dir":`, err)
+	}
+	defer RemoveAll("_test/dir")
+
+	err = Symlink("dir", "_test/link")
+	if err != nil {
+		t.Fatal(`Symlink "dir", "_test/link":`, err)
+	}
+	defer RemoveAll("_test/link")
+
+	path := "_test/link/foo"
+	err = MkdirAll(path, 0755)
+	if err != nil {
+		t.Errorf("MkdirAll %q: %s", path, err)
+	}
+}