os: pull in os.Rename and some of its tests from upstream

Skip part of the test on Windows because of #2480

TODO: fix 2480 and unskip test
TODO: pull in rest of upstream tests, fix problems they find

Requested in #2109

Author: dkegel-fastly

src/os/file_anyos.go

@@ -40,6 +40,14 @@ func Chdir(dir string) error {
 	return nil
 }
 
+// Rename renames (moves) oldpath to newpath.
+// If newpath already exists and is not a directory, Rename replaces it.
+// OS-specific restrictions may apply when oldpath and newpath are in different directories.
+// If there is an error, it will be of type *LinkError.
+func Rename(oldpath, newpath string) error {
+	return rename(oldpath, newpath)
+}
+
 // unixFilesystem is an empty handle for a Unix/Linux filesystem. All operations
 // are relative to the current working directory.
 type unixFilesystem struct {

src/os/file_unix.go

@@ -18,6 +18,15 @@ func fixLongPath(path string) string {
 	return path
 }
 
+func rename(oldname, newname string) error {
+	// TODO: import rest of upstream tests, handle fancy cases
+	err := syscall.Rename(oldname, newname)
+	if err != nil {
+		return &LinkError{"rename", oldname, newname, err}
+	}
+	return nil
+}
+
 func Pipe() (r *File, w *File, err error) {
 	var p [2]int
 	err = handleSyscallError(syscall.Pipe2(p[:], syscall.O_CLOEXEC))

src/os/file_windows.go

@@ -8,12 +8,21 @@
 package os
 
 import (
+	"internal/syscall/windows"
 	"syscall"
 	"unicode/utf16"
 )
 
 type syscallFd = syscall.Handle
 
+func rename(oldname, newname string) error {
+	e := windows.Rename(fixLongPath(oldname), fixLongPath(newname))
+	if e != nil {
+		return &LinkError{"rename", oldname, newname, e}
+	}
+	return nil
+}
+
 func Pipe() (r *File, w *File, err error) {
 	var p [2]syscall.Handle
 	e := handleSyscallError(syscall.Pipe(p[:]))

src/os/os_anyos_test.go

@@ -3,6 +3,7 @@
 package os_test
 
 import (
+	"io/ioutil"
 	. "os"
 	"path/filepath"
 	"runtime"
@@ -35,7 +36,7 @@ func TestMkdir(t *testing.T) {
 
 func TestStatBadDir(t *testing.T) {
 	if runtime.GOOS == "windows" {
-		t.Log("TODO: TestStatBadDir fails on Windows, skipping")
+		t.Log("TODO: TestStatBadDir: IsNotExist fails on Windows, skipping")
 		return
 	}
 	dir := TempDir()
@@ -94,3 +95,88 @@ func TestRemove(t *testing.T) {
 		t.Fatalf("Remove: %v", err)
 	}
 }
+
+func TestRename(t *testing.T) {
+	// TODO: use t.TempDir()
+	from, to := TempDir()+"/"+"TestRename-from", TempDir()+"/"+"TestRename-to"
+
+	file, err := Create(from)
+	defer Remove(from) // TODO: switch to t.Tempdir, remove this line
+	if err != nil {
+		t.Fatalf("open %q failed: %v", from, err)
+	}
+	defer Remove(to) // TODO: switch to t.Tempdir, remove this line
+	if err = file.Close(); err != nil {
+		t.Errorf("close %q failed: %v", from, err)
+	}
+	err = Rename(from, to)
+	if err != nil {
+		t.Fatalf("rename %q, %q failed: %v", to, from, err)
+	}
+	_, err = Stat(to)
+	if err != nil {
+		t.Errorf("stat %q failed: %v", to, err)
+	}
+}
+
+func TestRenameOverwriteDest(t *testing.T) {
+	from, to := TempDir()+"/"+"TestRenameOverwrite-from", TempDir()+"/"+"TestRenameOverwrite-to"
+
+	toData := []byte("to")
+	fromData := []byte("from")
+
+	err := ioutil.WriteFile(to, toData, 0777)
+	defer Remove(to) // TODO: switch to t.Tempdir, remove this line
+	if err != nil {
+		t.Fatalf("write file %q failed: %v", to, err)
+	}
+
+	err = ioutil.WriteFile(from, fromData, 0777)
+	defer Remove(from) // TODO: switch to t.Tempdir, remove this line
+	if err != nil {
+		t.Fatalf("write file %q failed: %v", from, err)
+	}
+	err = Rename(from, to)
+	if err != nil {
+		t.Fatalf("rename %q, %q failed: %v", to, from, err)
+	}
+
+	_, err = Stat(from)
+	if err == nil {
+		t.Errorf("from file %q still exists", from)
+	}
+	if runtime.GOOS == "windows" {
+		t.Log("TODO: TestRenameOverwriteDest: IsNotExist fails on Windows, skipping")
+	} else if err != nil && !IsNotExist(err) {
+		t.Fatalf("stat from: %v", err)
+	}
+	toFi, err := Stat(to)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", to, err)
+	}
+	if toFi.Size() != int64(len(fromData)) {
+		t.Errorf(`"to" size = %d; want %d (old "from" size)`, toFi.Size(), len(fromData))
+	}
+}
+
+func TestRenameFailed(t *testing.T) {
+	from, to := TempDir()+"/"+"RenameFailed-from", TempDir()+"/"+"RenameFailed-to"
+
+	err := Rename(from, to)
+	switch err := err.(type) {
+	case *LinkError:
+		if err.Op != "rename" {
+			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
+		}
+		if err.Old != from {
+			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
+		}
+		if err.New != to {
+			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
+		}
+	case nil:
+		t.Errorf("rename %q, %q: expected error, got nil", from, to)
+	default:
+		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
+	}
+}

src/syscall/syscall_libc.go

@@ -95,6 +95,16 @@ func Rmdir(path string) (err error) {
 	return
 }
 
+func Rename(from, to string) (err error) {
+	fromdata := cstring(from)
+	todata := cstring(to)
+	fail := int(libc_rename(&fromdata[0], &todata[0]))
+	if fail < 0 {
+		err = getErrno()
+	}
+	return
+}
+
 func Unlink(path string) (err error) {
 	data := cstring(path)
 	fail := int(libc_unlink(&data[0]))
@@ -270,6 +280,10 @@ func libc_mkdir(pathname *byte, mode uint32) int32
 //export rmdir
 func libc_rmdir(pathname *byte) int32
 
+// int rename(const char *from, *to);
+//export rename
+func libc_rename(from, too *byte) int32
+
 // int unlink(const char *pathname);
 //export unlink
 func libc_unlink(pathname *byte) int32