schema/mixin: add support for mixed-in annotations

ent.go

@@ -153,6 +153,9 @@ type (
 		// Policy returns a privacy policy to add to the schema.
 		// Note that mixin policy are executed before schema policy.
 		Policy() Policy
+		// Annotations returns a list of schema annotations to add
+		// to the schema annotations.
+		Annotations() []schema.Annotation
 	}
 
 	// The Policy type defines the write privacy policy of an entity.

entc/load/schema.go

@@ -158,12 +158,13 @@ func MarshalSchema(schema ent.Interface) (b []byte, err error) {
 		Name:        indirect(reflect.TypeOf(schema)).Name(),
 		Annotations: make(map[string]interface{}),
 	}
-	for _, at := range schema.Annotations() {
-		s.Annotations[at.Name()] = at
-	}
 	if err := s.loadMixin(schema); err != nil {
 		return nil, fmt.Errorf("schema %q: %v", s.Name, err)
 	}
+	// Schema annotations override mixed-in annotations.
+	for _, at := range schema.Annotations() {
+		s.Annotations[at.Name()] = at
+	}
 	if err := s.loadFields(schema); err != nil {
 		return nil, fmt.Errorf("schema %q: %v", s.Name, err)
 	}
@@ -263,6 +264,9 @@ func (s *Schema) loadMixin(schema ent.Interface) error {
 				MixinIndex: i,
 			})
 		}
+		for _, at := range mx.Annotations() {
+			s.Annotations[at.Name()] = at
+		}
 	}
 	return nil
 }

entc/load/schema_test.go

@@ -30,14 +30,34 @@ func (OrderConfig) Name() string {
 	return "order_config"
 }
 
-func (o *OrderConfig) MarshalJSON() ([]byte, error) {
-	return json.Marshal(*o)
+type IDConfig struct {
+	TagName string
+}
+
+func (IDConfig) Name() string {
+	return "id_config"
+}
+
+type AnnotationMixin struct {
+	mixin.Schema
+}
+
+func (AnnotationMixin) Annotations() []schema.Annotation {
+	return []schema.Annotation{
+		IDConfig{TagName: "id tag"},
+	}
 }
 
 type User struct {
 	ent.Schema
 }
 
+func (User) Mixin() []ent.Mixin {
+	return []ent.Mixin{
+		AnnotationMixin{},
+	}
+}
+
 func (User) Annotations() []schema.Annotation {
 	return []schema.Annotation{
 		OrderConfig{FieldName: "type annotations"},
@@ -110,7 +130,7 @@ func TestMarshalSchema(t *testing.T) {
 		schema, err := UnmarshalSchema(buf)
 		require.NoError(t, err)
 		require.Equal(t, "User", schema.Name)
-		require.Len(t, schema.Annotations, 1)
+		require.Len(t, schema.Annotations, 2)
 		ant := schema.Annotations["order_config"].(map[string]interface{})
 		require.Equal(t, ant["FieldName"], "type annotations")
 

schema/mixin/mixin.go

@@ -36,6 +36,9 @@ func (Schema) Hooks() []ent.Hook { return nil }
 // Policy of the mixin.
 func (Schema) Policy() ent.Policy { return nil }
 
+// Annotations of the mixin.
+func (Schema) Annotations() []schema.Annotation { return nil }
+
 // time mixin must implement `Mixin` interface.
 var _ ent.Mixin = (*Schema)(nil)