os: IsNotExist() should also consider ERROR_PATH_NOT_FOUND on Windows

Also update documentation about IsExist() and IsNotExist(), they are not
    about files only.

R=rsc
CC=golang-dev
https://golang.org/cl/5794073

src/pkg/os/error.go

@@ -43,14 +43,14 @@ func NewSyscallError(syscall string, err error) error {
 	return &SyscallError{syscall, err}
 }
 
-// IsExist returns whether the error is known to report that a file already exists.
+// IsExist returns whether the error is known to report that a file or directory 
-// It is satisfied by ErrExist as well as some syscall errors.
+// already exists. It is satisfied by ErrExist as well as some syscall errors.
 func IsExist(err error) bool {
 	return isExist(err)
 }
 
-// IsNotExist returns whether the error is known to report that a file does not exist.
+// IsNotExist returns whether the error is known to report that a file or directory
-// It is satisfied by ErrNotExist as well as some syscall errors.
+// does not exist. It is satisfied by ErrNotExist as well as some syscall errors.
 func IsNotExist(err error) bool {
 	return isNotExist(err)
 }

src/pkg/os/error_test.go

@@ -5,8 +5,10 @@
 package os_test
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
+	"path/filepath"
 	"testing"
 )
 
@@ -24,8 +26,56 @@ func TestErrIsExist(t *testing.T) {
 		t.Fatal("Open should have failed")
 		return
 	}
-	if !os.IsExist(err) {
+	if s := checkErrorPredicate("os.IsExist", os.IsExist, err); s != "" {
-		t.Fatalf("os.IsExist does not work as expected for %#v", err)
+		t.Fatal(s)
 		return
 	}
 }
+
+func testErrNotExist(name string) string {
+	f, err := os.Open(name)
+	if err == nil {
+		f.Close()
+		return "Open should have failed"
+	}
+	if s := checkErrorPredicate("os.IsNotExist", os.IsNotExist, err); s != "" {
+		return s
+	}
+
+	err = os.Chdir(name)
+	if err == nil {
+		return "Chdir should have failed"
+	}
+	if s := checkErrorPredicate("os.IsNotExist", os.IsNotExist, err); s != "" {
+		return s
+	}
+	return ""
+}
+
+func TestErrIsNotExist(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("", "_Go_ErrIsNotExist")
+	if err != nil {
+		t.Fatalf("create ErrIsNotExist tempdir: %s", err)
+		return
+	}
+	defer os.RemoveAll(tmpDir)
+
+	name := filepath.Join(tmpDir, "NotExists")
+	if s := testErrNotExist(name); s != "" {
+		t.Fatal(s)
+		return
+	}
+
+	name = filepath.Join(name, "NotExists2")
+	if s := testErrNotExist(name); s != "" {
+		t.Fatal(s)
+		return
+	}
+}
+
+func checkErrorPredicate(predName string, pred func(error) bool, err error) string {
+	if !pred(err) {
+		return fmt.Sprintf("%s does not work as expected for %#v", predName, err)
+	}
+	return ""
+}

src/pkg/os/error_windows.go

@@ -10,7 +10,7 @@ func isExist(err error) bool {
 	if pe, ok := err.(*PathError); ok {
 		err = pe.Err
 	}
-	return err == syscall.EEXIST || err == syscall.ERROR_ALREADY_EXISTS ||
+	return err == syscall.ERROR_ALREADY_EXISTS ||
 		err == syscall.ERROR_FILE_EXISTS || err == ErrExist
 }
 
@@ -18,12 +18,13 @@ func isNotExist(err error) bool {
 	if pe, ok := err.(*PathError); ok {
 		err = pe.Err
 	}
-	return err == syscall.ENOENT || err == ErrNotExist
+	return err == syscall.ERROR_FILE_NOT_FOUND ||
+		err == syscall.ERROR_PATH_NOT_FOUND || err == ErrNotExist
 }
 
 func isPermission(err error) bool {
 	if pe, ok := err.(*PathError); ok {
 		err = pe.Err
 	}
-	return err == syscall.EACCES || err == syscall.EPERM || err == ErrPermission
+	return err == ErrPermission
 }