os: return a *PathError from Readdirnames and Readdir on POSIX platforms

Previously, Readdirnames returned a *PathError on Windows and Plan 9,
but a *SyscallError on POSIX systems.

In contrast, similar methods (such as Stat) return a *PathError on all platforms.

Fixes #38923

Change-Id: I26395905b1e723933f07b792c7aeee7c335949cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/233917
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

3 files changed, 10 insertions, 6 deletions

diff --git a/src/os/dir_darwin.go b/src/os/dir_darwin.go
index 87797e2dda..476af6862e 100644
--- a/src/os/dir_darwin.go
+++ b/src/os/dir_darwin.go
@@ -28,7 +28,7 @@ func (f *File) readdirnames(n int) (names []string, err error) {
 	if f.dirinfo == nil {
 		dir, call, errno := f.pfd.OpenDir()
 		if errno != nil {
-			return nil, wrapSyscallError(call, errno)
+			return nil, &PathError{call, f.name, errno}
 		}
 		f.dirinfo = &dirInfo{
 			dir: dir,
@@ -46,11 +46,11 @@ func (f *File) readdirnames(n int) (names []string, err error) {
 	var dirent syscall.Dirent
 	var entptr *syscall.Dirent
 	for len(names) < size || n == -1 {
-		if res := readdir_r(d.dir, &dirent, &entptr); res != 0 {
-			if syscall.Errno(res) == syscall.EINTR {
+		if errno := readdir_r(d.dir, &dirent, &entptr); errno != 0 {
+			if errno == syscall.EINTR {
 				continue
 			}
-			return names, wrapSyscallError("readdir", syscall.Errno(res))
+			return names, &PathError{"readdir", f.name, errno}
 		}
 		if entptr == nil { // EOF
 			break
@@ -84,4 +84,4 @@ func (f *File) readdirnames(n int) (names []string, err error) {
 func closedir(dir uintptr) (err error)
 
 //go:linkname readdir_r syscall.readdir_r
-func readdir_r(dir uintptr, entry *syscall.Dirent, result **syscall.Dirent) (res int)
+func readdir_r(dir uintptr, entry *syscall.Dirent, result **syscall.Dirent) (res syscall.Errno)
diff --git a/src/os/dir_unix.go b/src/os/dir_unix.go
index e0c4989756..58ec406ab8 100644
--- a/src/os/dir_unix.go
+++ b/src/os/dir_unix.go
@@ -50,7 +50,7 @@ func (f *File) readdirnames(n int) (names []string, err error) {
 			d.nbuf, errno = f.pfd.ReadDirent(d.buf)
 			runtime.KeepAlive(f)
 			if errno != nil {
-				return names, wrapSyscallError("readdirent", errno)
+				return names, &PathError{"readdirent", f.name, errno}
 			}
 			if d.nbuf <= 0 {
 				break // EOF
diff --git a/src/os/os_test.go b/src/os/os_test.go
index e8c64510f5..520916d880 100644
--- a/src/os/os_test.go
+++ b/src/os/os_test.go
@@ -688,6 +688,10 @@ func TestReaddirOfFile(t *testing.T) {
 	if err == nil {
 		t.Error("Readdirnames succeeded; want non-nil error")
 	}
+	var pe *PathError
+	if !errors.As(err, &pe) || pe.Path != f.Name() {
+		t.Errorf("Readdirnames returned %q; want a PathError with path %q", err, f.Name())
+	}
 	if len(names) > 0 {
 		t.Errorf("unexpected dir names in regular file: %q", names)
 	}