Merge pull request #62 from goccy/feature/fix-decoding-for-struct

Supports default value in decoding for struct

decode.go

@@ -529,7 +529,6 @@ func (d *Decoder) decodeStruct(dst reflect.Value, src ast.Node) error {
 		return nil
 	}
 	structType := dst.Type()
-	structValue := reflect.New(structType)
 	structFieldMap, err := structFieldMap(structType)
 	if err != nil {
 		return errors.Wrapf(err, "failed to create struct field map")
@@ -555,7 +554,7 @@ func (d *Decoder) decodeStruct(dst reflect.Value, src ast.Node) error {
 		}
 		structField := structFieldMap[field.Name]
 		if structField.IsInline {
-			fieldValue := structValue.Elem().FieldByName(field.Name)
+			fieldValue := dst.FieldByName(field.Name)
 			if !fieldValue.CanSet() {
 				return xerrors.Errorf("cannot set embedded type as unexported field %s.%s", field.PkgPath, field.Name)
 			}
@@ -593,7 +592,7 @@ func (d *Decoder) decodeStruct(dst reflect.Value, src ast.Node) error {
 			continue
 		}
 		delete(unknownFields, structField.RenderName)
-		fieldValue := structValue.Elem().FieldByName(field.Name)
+		fieldValue := dst.FieldByName(field.Name)
 		if fieldValue.Type().Kind() == reflect.Ptr && src.Type() == ast.NullType {
 			// set nil value to pointer
 			fieldValue.Set(reflect.Zero(fieldValue.Type()))
@@ -617,7 +616,7 @@ func (d *Decoder) decodeStruct(dst reflect.Value, src ast.Node) error {
 		fieldValue.Set(d.castToAssignableValue(newFieldValue, fieldValue.Type()))
 	}
 	if d.validator != nil {
-		if err := d.validator.Struct(structValue.Interface()); err != nil {
+		if err := d.validator.Struct(dst.Interface()); err != nil {
 			ev := reflect.ValueOf(err)
 			if ev.Type().Kind() == reflect.Slice {
 				for i := 0; i < ev.Len(); i++ {
@@ -641,7 +640,6 @@ func (d *Decoder) decodeStruct(dst reflect.Value, src ast.Node) error {
 			return errors.ErrSyntax(fmt.Sprintf(`unknown field "%s"`, key), node.GetToken())
 		}
 	}
-	dst.Set(structValue.Elem())
 	if foundErr != nil {
 		return errors.Wrapf(foundErr, "failed to decode value")
 	}

decode_test.go

@@ -1194,6 +1194,35 @@ b_yaml: b_yaml_value
 	}
 }
 
+func TestDecoder_DefaultValues(t *testing.T) {
+	v := struct {
+		A string `yaml:"a"`
+		B string `yaml:"b"`
+		c string // private
+	}{
+		B: "defaultBValue",
+		c: "defaultCValue",
+	}
+
+	const src = `---
+a: a_value
+`
+	if err := yaml.NewDecoder(strings.NewReader(src)).Decode(&v); err != nil {
+		t.Fatalf(`parsing should succeed: %s`, err)
+	}
+	if v.A != "a_value" {
+		t.Fatalf("v.A should be `a_value`, got `%s`", v.A)
+	}
+
+	if v.B != "defaultBValue" {
+		t.Fatalf("v.B should be `defaultValue`, got `%s`", v.B)
+	}
+
+	if v.c != "defaultCValue" {
+		t.Fatalf("v.c should be `defaultCValue`, got `%s`", v.c)
+	}
+}
+
 func Example_YAMLTags() {
 	yml := `---
 foo: 1