Return error from Rename function

Rename should return also an error, which will be wrapped and returned from Mapper.MapAny method. This is the only way to stop the conversion when there is something wrong with renaming.

Author: elgopher

defaults.go

@@ -7,8 +7,8 @@ func acceptAllFields(string, Element) (bool, error) {
 	return true, nil
 }
 
-func noRename(_ string, e Element) string {
-	return e.Name()
+func noRename(_ string, e Element) (string, error) {
+	return e.Name(), nil
 }
 
 func interfaceValue(_ string, e Element) (interface{}, error) {

mapify.go

@@ -21,8 +21,9 @@ type Mapper struct {
 // and wrapped error is returned from Mapper.MapAny method.
 type Filter func(path string, e Element) (bool, error)
 
-// Rename renames element name.
-type Rename func(path string, e Element) string
+// Rename renames element name. If error is returned then the whole conversion is aborted
+// and wrapped error is returned from Mapper.MapAny method.
+type Rename func(path string, e Element) (string, error)
 
 // MapValue maps (transforms) element value. If error is returned then the whole conversion is aborted
 // and wrapped error is returned from Mapper.MapAny method.
@@ -96,7 +97,11 @@ func (i Mapper) mapStruct(path string, reflectValue reflect.Value) (map[string]i
 		}
 
 		if accepted {
-			renamed := i.Rename(fieldPath, element)
+			renamed, err := i.Rename(fieldPath, element)
+			if err != nil {
+				return nil, fmt.Errorf("Rename failed: %w", err)
+			}
+
 			mappedValue, err := i.MapValue(fieldPath, element)
 			if err != nil {
 				return nil, fmt.Errorf("MapValue failed: %w", err)

mapify_test.go

@@ -417,14 +417,13 @@ func TestFilter(t *testing.T) {
 		assert.Nil(t, result)
 		assert.ErrorIs(t, actualErr, givenError)
 	})
-
 }
 
 func TestRename(t *testing.T) {
 	t.Run("should rename struct field", func(t *testing.T) {
 		mapper := mapify.Mapper{
-			Rename: func(path string, e mapify.Element) string {
-				return "newName"
+			Rename: func(path string, e mapify.Element) (string, error) {
+				return "newName", nil
 			},
 		}
 		// when
@@ -440,6 +439,20 @@ func TestRename(t *testing.T) {
 		}
 		assert.Equal(t, expected, v)
 	})
+
+	t.Run("should return error when Rename returned error", func(t *testing.T) {
+		givenError := stringError("err")
+		mapper := mapify.Mapper{
+			Rename: func(path string, e mapify.Element) (string, error) {
+				return e.Name(), givenError
+			},
+		}
+		// when
+		result, actualErr := mapper.MapAny(struct{ Field string }{})
+		// then
+		assert.Nil(t, result)
+		assert.ErrorIs(t, actualErr, givenError)
+	})
 }
 
 func TestMapValue(t *testing.T) {