os: make sure Remove returns correct error on windows

R=golang-dev, bsiegert, rsc
CC=golang-dev
https://golang.org/cl/5493078

src/pkg/os/file_posix.go

@@ -24,39 +24,6 @@ func epipecheck(file *File, e error) {
 	}
 }
 
-// Remove removes the named file or directory.
-func Remove(name string) error {
-	// System call interface forces us to know
-	// whether name is a file or directory.
-	// Try both: it is cheaper on average than
-	// doing a Stat plus the right one.
-	e := syscall.Unlink(name)
-	if e == nil {
-		return nil
-	}
-	e1 := syscall.Rmdir(name)
-	if e1 == nil {
-		return nil
-	}
-
-	// Both failed: figure out which error to return.
-	// OS X and Linux differ on whether unlink(dir)
-	// returns EISDIR, so can't use that.  However,
-	// both agree that rmdir(file) returns ENOTDIR,
-	// so we can use that to decide which error is real.
-	// Rmdir might also return ENOTDIR if given a bad
-	// file path, like /etc/passwd/foo, but in that case,
-	// both errors will be ENOTDIR, so it's okay to
-	// use the error from unlink.
-	// For windows syscall.ENOTDIR is set
-	// to syscall.ERROR_PATH_NOT_FOUND, hopefully it should
-	// do the trick.
-	if e1 != syscall.ENOTDIR {
-		e = e1
-	}
-	return &PathError{"remove", name, e}
-}
-
 // LinkError records an error during a link or symlink or rename
 // system call and the paths that caused it.
 type LinkError struct {

src/pkg/os/file_unix.go

@@ -210,6 +210,36 @@ func Truncate(name string, size int64) error {
 	return nil
 }
 
+// Remove removes the named file or directory.
+func Remove(name string) error {
+	// System call interface forces us to know
+	// whether name is a file or directory.
+	// Try both: it is cheaper on average than
+	// doing a Stat plus the right one.
+	e := syscall.Unlink(name)
+	if e == nil {
+		return nil
+	}
+	e1 := syscall.Rmdir(name)
+	if e1 == nil {
+		return nil
+	}
+
+	// Both failed: figure out which error to return.
+	// OS X and Linux differ on whether unlink(dir)
+	// returns EISDIR, so can't use that.  However,
+	// both agree that rmdir(file) returns ENOTDIR,
+	// so we can use that to decide which error is real.
+	// Rmdir might also return ENOTDIR if given a bad
+	// file path, like /etc/passwd/foo, but in that case,
+	// both errors will be ENOTDIR, so it's okay to
+	// use the error from unlink.
+	if e1 != syscall.ENOTDIR {
+		e = e1
+	}
+	return &PathError{"remove", name, e}
+}
+
 // basename removes trailing slashes and the leading directory name from path name
 func basename(name string) string {
 	i := len(name) - 1

src/pkg/os/file_windows.go

@@ -281,6 +281,35 @@ func Truncate(name string, size int64) error {
 	return nil
 }
 
+// Remove removes the named file or directory.
+func Remove(name string) error {
+	p := &syscall.StringToUTF16(name)[0]
+
+	// Go file interface forces us to know whether
+	// name is a file or directory. Try both.
+	e := syscall.DeleteFile(p)
+	if e == nil {
+		return nil
+	}
+	e1 := syscall.RemoveDirectory(p)
+	if e1 == nil {
+		return nil
+	}
+
+	// Both failed: figure out which error to return.
+	if e1 != e {
+		a, e2 := syscall.GetFileAttributes(p)
+		if e2 != nil {
+			e = e2
+		} else {
+			if a&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
+				e = e1
+			}
+		}
+	}
+	return &PathError{"remove", name, e}
+}
+
 // Pipe returns a connected pair of Files; reads from r return bytes written to w.
 // It returns the files and an error, if any.
 func Pipe() (r *File, w *File, err error) {