support tag with map value

ast/ast.go

@@ -1414,7 +1414,10 @@ func (n *MappingValueNode) toString() string {
 		return fmt.Sprintf("%s%s: %s", space, n.Key.String(), n.Value.String())
 	} else if _, ok := n.Value.(*AliasNode); ok {
 		return fmt.Sprintf("%s%s: %s", space, n.Key.String(), n.Value.String())
-	} else if _, ok := n.Value.(*TagNode); ok {
+	} else if tn, ok := n.Value.(*TagNode); ok {
+		if _, xok := tn.Value.(MapNode); xok {
+			return fmt.Sprintf("%s%s:%s", space, n.Key.String(), n.Value.String())
+		}
 		return fmt.Sprintf("%s%s: %s", space, n.Key.String(), n.Value.String())
 	}
 	if keyComment != nil {
@@ -1797,6 +1800,16 @@ func (n *TagNode) AddColumn(col int) {
 
 // String tag to text
 func (n *TagNode) String() string {
+	space := strings.Repeat(" ", n.GetToken().Position.Column-1)
+
+	value := n.Value.String()
+	if s, ok := n.Value.(*SequenceNode); ok && !s.IsFlowStyle {
+		return fmt.Sprintf("%s\n%s", n.Start.Value, value)
+	} else if m, ok := n.Value.(*MappingNode); ok && !m.IsFlowStyle {
+		return fmt.Sprintf("\n%s%s\n%s", space, n.Start.Value, value)
+	} else if _, ok := n.Value.(*MappingValueNode); ok {
+		return fmt.Sprintf("\n%s%s\n%s", space, n.Start.Value, value)
+	}
 	return fmt.Sprintf("%s %s", n.Start.Value, n.Value.String())
 }
 

encode.go

@@ -609,6 +609,9 @@ func (e *Encoder) encodeMapItem(ctx context.Context, item MapItem, column int) (
 	if e.isMapNode(value) {
 		value.AddColumn(e.indent)
 	}
+	if e.isTagAndMapNode(value) {
+		value.AddColumn(e.indent)
+	}
 	return ast.MappingValue(
 		token.New("", "", e.pos(column)),
 		e.encodeString(k.Interface().(string), column),
@@ -633,6 +636,14 @@ func (e *Encoder) isMapNode(node ast.Node) bool {
 	return ok
 }
 
+func (e *Encoder) isTagAndMapNode(node ast.Node) bool {
+	tn, ok := node.(*ast.TagNode)
+	if ok {
+		_, ok = tn.Value.(ast.MapNode)
+	}
+	return ok
+}
+
 func (e *Encoder) encodeMap(ctx context.Context, value reflect.Value, column int) ast.Node {
 	node := ast.Mapping(token.New("", "", e.pos(column)), e.isFlowStyle)
 	keys := make([]interface{}, len(value.MapKeys()))
@@ -652,6 +663,9 @@ func (e *Encoder) encodeMap(ctx context.Context, value reflect.Value, column int
 		if e.isMapNode(value) {
 			value.AddColumn(e.indent)
 		}
+		if e.isTagAndMapNode(value) {
+			value.AddColumn(e.indent)
+		}
 		node.Values = append(node.Values, ast.MappingValue(
 			nil,
 			e.encodeString(fmt.Sprint(key), column),

encode_test.go

@@ -1666,3 +1666,73 @@ a:
 		t.Fatalf("failed to encode. expected %s but got %s", expected, got)
 	}
 }
+
+type tagMarshalerMapValue struct {
+	Tag   string
+	Value any
+}
+
+func (t *tagMarshalerMapValue) MarshalYAML() ([]byte, error) {
+	var out bytes.Buffer
+	_, _ = fmt.Fprintf(&out, "\n%s\n", t.Tag)
+	v, err := yaml.ValueToNode(t.Value, yaml.Flow(false))
+	if err != nil {
+		return nil, err
+	}
+	_, _ = fmt.Fprintf(&out, "%s", v)
+	return out.Bytes(), nil
+}
+
+func TestTagMarshalerMapValue(t *testing.T) {
+	b, err := yaml.Marshal(map[string]interface{}{
+		"a": map[string]interface{}{
+			"b": &tagMarshalerMapValue{
+				Tag: "!mytag",
+				Value: map[string]interface{}{
+					"c": 15,
+					"d": 99,
+				},
+			},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := `
+a:
+  b:
+    !mytag
+    c: 15
+    d: 99
+`
+	got := "\n" + string(b)
+	if expected != got {
+		t.Fatalf("failed to encode. expected %s but got %s", expected, got)
+	}
+}
+
+func TestTagMarshalerMapValue2(t *testing.T) {
+	b, err := yaml.Marshal(map[string]interface{}{
+		"a": map[string]interface{}{
+			"b": &tagMarshalerMapValue{
+				Tag: "!mytag",
+				Value: map[string]interface{}{
+					"c": 15,
+				},
+			},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := `
+a:
+  b:
+    !mytag
+    c: 15
+`
+	got := "\n" + string(b)
+	if expected != got {
+		t.Fatalf("failed to encode. expected %s but got %s", expected, got)
+	}
+}