helper.Duplicate uses openfile.

internal/helper/os.go

@@ -89,13 +89,16 @@ func Count(dir string) (int, error) {
 
 // Duplicate is a workaround for renaming files across different devices.
 // A cross device can also be a different file system such as a Docker volume.
+// It returns the number of bytes written to the new file.
 func Duplicate(oldpath, newpath string) (int64, error) {
 	src, err := os.Open(oldpath)
 	if err != nil {
 		return 0, fmt.Errorf("duplicate os.open %w", err)
 	}
 	defer src.Close()
-	dst, err := os.Create(newpath)
+
+	const createNoTruncate = os.O_CREATE | os.O_WRONLY | os.O_EXCL
+	dst, err := os.OpenFile(newpath, createNoTruncate, WriteWriteRead)
 	if err != nil {
 		return 0, fmt.Errorf("duplicate os.create %w", err)
 	}
@@ -105,10 +108,6 @@ func Duplicate(oldpath, newpath string) (int64, error) {
 	if err != nil {
 		return 0, fmt.Errorf("duplicate io.copy %w", err)
 	}
-	if err = os.Chmod(newpath, WriteWriteRead); err != nil {
-		defer os.Remove(newpath)
-		return 0, fmt.Errorf("duplicate os.chmod %d %w", WriteWriteRead, err)
-	}
 	return written, nil
 }
 

internal/helper/os_test.go

@@ -30,6 +30,46 @@ func TestCount(t *testing.T) {
 	assert.Equal(t, testDataFileCount, i)
 }
 
+func TestDuplicate(t *testing.T) {
+	dir, err := filepath.Abs("../../assets/testdata")
+	require.NoError(t, err)
+
+	r, err := helper.Duplicate(dir, "")
+	require.Error(t, err)
+	assert.Empty(t, r)
+	r, err = helper.Duplicate(dir, dir)
+	require.Error(t, err)
+	assert.Empty(t, r)
+
+	file, err := filepath.Abs("../../assets/testdata/uncompress/TEST.NFO")
+	require.NoError(t, err)
+
+	r, err = helper.Duplicate(file, "")
+	require.Error(t, err)
+	assert.Empty(t, r)
+
+	r, err = helper.Duplicate("", file)
+	require.Error(t, err)
+	assert.Empty(t, r)
+
+	r, err = helper.Duplicate(file, file)
+	require.Error(t, err)
+	assert.Empty(t, r)
+
+	dest, err := os.MkdirTemp(os.TempDir(), "test_duplicate")
+	require.NoError(t, err)
+	defer os.RemoveAll(dest)
+
+	r, err = helper.Duplicate(file, dest)
+	require.Error(t, err)
+	assert.Empty(t, r)
+
+	dest = filepath.Join(dest, "TEST.NFO")
+	written, err := helper.Duplicate(file, dest)
+	require.NoError(t, err)
+	assert.Equal(t, written, int64(13))
+}
+
 func TestFiles(t *testing.T) {
 	dir, err := filepath.Abs("../../assets/testdata")
 	require.NoError(t, err)