Call MarshalYAML on embedded structures

encode.go

@@ -100,6 +100,22 @@ func (e *encoder) marshal(tag string, in reflect.Value) {
 		e.nilv()
 		return
 	}
+	// In case of embedded fields, let's get a poiter etc.
+	if in.CanAddr() {
+		m, ok := in.Addr().Interface().(Marshaler)
+		if ok {
+			v, err := m.MarshalYAML()
+			if err != nil {
+				fail(err)
+			}
+			if v == nil {
+				e.nilv()
+				return
+			}
+			in = reflect.ValueOf(v)
+		}
+	}
+
 	iface := in.Interface()
 	switch m := iface.(type) {
 	case jsonNumber:

encode_test.go

@@ -35,10 +35,24 @@ func (j jsonNumberT) String() string {
 
 var marshalIntTest = 123
 
+type Outer struct {
+	Inner Inner
+}
+
+type Inner struct{}
+
+func (i *Inner) MarshalYAML() (interface{}, error) {
+	return "foo", nil
+}
+
 var marshalTests = []struct {
 	value interface{}
 	data  string
 }{
+	{
+		&Outer{},
+		"inner: foo\n",
+	},
 	{
 		nil,
 		"null\n",
@@ -406,8 +420,8 @@ func (s *S) TestLineWrapping(c *C) {
 	data, err := yaml.Marshal(v)
 	c.Assert(err, IsNil)
 	c.Assert(string(data), Equals,
-		"a: 'abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890 abcdefghijklmnopqrstuvwxyz\n" +
-		"  ABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890 '\n")
+		"a: 'abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890 abcdefghijklmnopqrstuvwxyz\n"+
+			"  ABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890 '\n")
 
 	// The API does not allow this process to be reversed as it's intended
 	// for migration only. v3 drops this method and instead offers more

go.mod

@@ -1,4 +1,4 @@
-module gopkg.in/yaml.v2
+module github.com/sustrik/yaml
 
 go 1.15