dynamic: support nested persistence

pkg/dynamic/iterate.go

@@ -52,6 +52,10 @@ func IterateFields(obj interface{}, cb func(ft reflect.StructField, fv reflect.V
 	return nil
 }
 
+func isStructPtr(tpe reflect.Type) bool {
+	return tpe.Kind() == reflect.Ptr && tpe.Elem().Kind() == reflect.Struct
+}
+
 func IterateFieldsByTag(obj interface{}, tagName string, cb StructFieldIterator) error {
 	sv := reflect.ValueOf(obj)
 	st := reflect.TypeOf(obj)
@@ -82,11 +86,19 @@ func IterateFieldsByTag(obj interface{}, tagName string, cb StructFieldIterator)
 			continue
 		}
 
+		if isStructPtr(ft.Type) && !fv.IsNil() {
+			// recursive iterate the struct field
+			if err := IterateFieldsByTag(fv.Interface(), tagName, cb); err != nil {
+				return fmt.Errorf("unable to iterate struct fields over the type %v: %v", ft, err)
+			}
+		}
+
 		tag, ok := ft.Tag.Lookup(tagName)
 		if !ok {
 			continue
 		}
 
+		// call the iterator
 		if err := cb(tag, ft, fv); err != nil {
 			return err
 		}

pkg/dynamic/iterate_test.go

@@ -40,5 +40,64 @@ func TestIterateFields(t *testing.T) {
 		assert.Error(t, err)
 	})
 
-
+}
+
+func TestIterateFieldsByTag(t *testing.T) {
+	t.Run("nested", func(t *testing.T) {
+		var a = struct {
+			A int `persistence:"a"`
+			B int `persistence:"b"`
+			C *struct {
+				D int `persistence:"d"`
+				E int `persistence:"e"`
+			}
+		}{
+			A: 1,
+			B: 2,
+			C: &struct {
+				D int `persistence:"d"`
+				E int `persistence:"e"`
+			}{
+				D: 3,
+				E: 4,
+			},
+		}
+
+		collectedTags := []string{}
+		cnt := 0
+		err := IterateFieldsByTag(&a, "persistence", func(tag string, ft reflect.StructField, fv reflect.Value) error {
+			cnt++
+			collectedTags = append(collectedTags, tag)
+			return nil
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, 4, cnt)
+		assert.Equal(t, []string{"a", "b", "d", "e"}, collectedTags)
+	})
+
+	t.Run("nested nil", func(t *testing.T) {
+		var a = struct {
+			A int `persistence:"a"`
+			B int `persistence:"b"`
+			C *struct {
+				D int `persistence:"d"`
+				E int `persistence:"e"`
+			}
+		}{
+			A: 1,
+			B: 2,
+			C: nil,
+		}
+
+		collectedTags := []string{}
+		cnt := 0
+		err := IterateFieldsByTag(&a, "persistence", func(tag string, ft reflect.StructField, fv reflect.Value) error {
+			cnt++
+			collectedTags = append(collectedTags, tag)
+			return nil
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, 2, cnt)
+		assert.Equal(t, []string{"a", "b"}, collectedTags)
+	})
 }