jsonpb: unmarshal JSON "null" for WKT (#394)

Properly unmarshal JSON "null" field value to nil for all WKTs except for Value type.  This is consistent with regular message field types.

jsonpb/jsonpb.go

@@ -639,7 +639,13 @@ func (u *Unmarshaler) unmarshalValue(target reflect.Value, inputValue json.RawMe
 
 	// Allocate memory for pointer fields.
 	if targetType.Kind() == reflect.Ptr {
+		// If input value is "null" and target is a pointer type, then the field should be treated as not set
+		// UNLESS the target is structpb.Value, in which case it should be set to structpb.NullValue.
+		if string(inputValue) == "null" && targetType != reflect.TypeOf(&stpb.Value{}) {
+			return nil
+		}
 		target.Set(reflect.New(targetType.Elem()))
+
 		return u.unmarshalValue(target.Elem(), inputValue, prop)
 	}
 
@@ -647,15 +653,11 @@ func (u *Unmarshaler) unmarshalValue(target reflect.Value, inputValue json.RawMe
 		return jsu.UnmarshalJSONPB(u, []byte(inputValue))
 	}
 
-	// Handle well-known types.
+	// Handle well-known types that are not pointers.
 	if w, ok := target.Addr().Interface().(wkt); ok {
 		switch w.XXX_WellKnownType() {
 		case "DoubleValue", "FloatValue", "Int64Value", "UInt64Value",
 			"Int32Value", "UInt32Value", "BoolValue", "StringValue", "BytesValue":
-			// "Wrappers use the same representation in JSON
-			//  as the wrapped primitive type, except that null is allowed."
-			// encoding/json will turn JSON `null` into Go `nil`,
-			// so we don't have to do any extra work.
 			return u.unmarshalValue(target.Field(0), inputValue, prop)
 		case "Any":
 			// Use json.RawMessage pointer type instead of value to support pre-1.8 version.
@@ -716,21 +718,16 @@ func (u *Unmarshaler) unmarshalValue(target reflect.Value, inputValue json.RawMe
 
 			return nil
 		case "Duration":
-			ivStr := string(inputValue)
-			if ivStr == "null" {
-				target.Field(0).SetInt(0)
-				target.Field(1).SetInt(0)
-				return nil
-			}
-
-			unq, err := strconv.Unquote(ivStr)
+			unq, err := strconv.Unquote(string(inputValue))
 			if err != nil {
 				return err
 			}
+
 			d, err := time.ParseDuration(unq)
 			if err != nil {
 				return fmt.Errorf("bad Duration: %v", err)
 			}
+
 			ns := d.Nanoseconds()
 			s := ns / 1e9
 			ns %= 1e9
@@ -738,33 +735,25 @@ func (u *Unmarshaler) unmarshalValue(target reflect.Value, inputValue json.RawMe
 			target.Field(1).SetInt(ns)
 			return nil
 		case "Timestamp":
-			ivStr := string(inputValue)
-			if ivStr == "null" {
-				target.Field(0).SetInt(0)
-				target.Field(1).SetInt(0)
-				return nil
-			}
-
-			unq, err := strconv.Unquote(ivStr)
+			unq, err := strconv.Unquote(string(inputValue))
 			if err != nil {
 				return err
 			}
+
 			t, err := time.Parse(time.RFC3339Nano, unq)
 			if err != nil {
 				return fmt.Errorf("bad Timestamp: %v", err)
 			}
+
 			target.Field(0).SetInt(t.Unix())
 			target.Field(1).SetInt(int64(t.Nanosecond()))
 			return nil
 		case "Struct":
-			if string(inputValue) == "null" {
-				// Interpret a null struct as empty.
-				return nil
-			}
 			var m map[string]json.RawMessage
 			if err := json.Unmarshal(inputValue, &m); err != nil {
 				return fmt.Errorf("bad StructValue: %v", err)
 			}
+
 			target.Field(0).Set(reflect.ValueOf(map[string]*stpb.Value{}))
 			for k, jv := range m {
 				pv := &stpb.Value{}
@@ -775,14 +764,11 @@ func (u *Unmarshaler) unmarshalValue(target reflect.Value, inputValue json.RawMe
 			}
 			return nil
 		case "ListValue":
-			if string(inputValue) == "null" {
-				// Interpret a null ListValue as empty.
-				return nil
-			}
 			var s []json.RawMessage
 			if err := json.Unmarshal(inputValue, &s); err != nil {
 				return fmt.Errorf("bad ListValue: %v", err)
 			}
+
 			target.Field(0).Set(reflect.ValueOf(make([]*stpb.Value, len(s), len(s))))
 			for i, sv := range s {
 				if err := u.unmarshalValue(target.Field(0).Index(i), sv, prop); err != nil {

jsonpb/jsonpb_test.go

@@ -553,12 +553,12 @@ var unmarshalingTests = []struct {
 	{"camelName input", Unmarshaler{}, `{"oBool":true}`, &pb.Simple{OBool: proto.Bool(true)}},
 
 	{"Duration", Unmarshaler{}, `{"dur":"3.000s"}`, &pb.KnownTypes{Dur: &durpb.Duration{Seconds: 3}}},
-	{"null Duration", Unmarshaler{}, `{"dur":null}`, &pb.KnownTypes{Dur: &durpb.Duration{Seconds: 0}}},
+	{"null Duration", Unmarshaler{}, `{"dur":null}`, &pb.KnownTypes{Dur: nil}},
 	{"Timestamp", Unmarshaler{}, `{"ts":"2014-05-13T16:53:20.021Z"}`, &pb.KnownTypes{Ts: &tspb.Timestamp{Seconds: 14e8, Nanos: 21e6}}},
 	{"PreEpochTimestamp", Unmarshaler{}, `{"ts":"1969-12-31T23:59:58.999999995Z"}`, &pb.KnownTypes{Ts: &tspb.Timestamp{Seconds: -2, Nanos: 999999995}}},
 	{"ZeroTimeTimestamp", Unmarshaler{}, `{"ts":"0001-01-01T00:00:00Z"}`, &pb.KnownTypes{Ts: &tspb.Timestamp{Seconds: -62135596800, Nanos: 0}}},
-	{"null Timestamp", Unmarshaler{}, `{"ts":null}`, &pb.KnownTypes{Ts: &tspb.Timestamp{Seconds: 0, Nanos: 0}}},
-	{"null Struct", Unmarshaler{}, `{"st": null}`, &pb.KnownTypes{St: &stpb.Struct{}}},
+	{"null Timestamp", Unmarshaler{}, `{"ts":null}`, &pb.KnownTypes{Ts: nil}},
+	{"null Struct", Unmarshaler{}, `{"st": null}`, &pb.KnownTypes{St: nil}},
 	{"empty Struct", Unmarshaler{}, `{"st": {}}`, &pb.KnownTypes{St: &stpb.Struct{}}},
 	{"basic Struct", Unmarshaler{}, `{"st": {"a": "x", "b": null, "c": 3, "d": true}}`, &pb.KnownTypes{St: &stpb.Struct{Fields: map[string]*stpb.Value{
 		"a": {Kind: &stpb.Value_StringValue{"x"}},
@@ -575,7 +575,7 @@ var unmarshalingTests = []struct {
 			}}}},
 		}}}},
 	}}}},
-	{"null ListValue", Unmarshaler{}, `{"lv": null}`, &pb.KnownTypes{Lv: &stpb.ListValue{}}},
+	{"null ListValue", Unmarshaler{}, `{"lv": null}`, &pb.KnownTypes{Lv: nil}},
 	{"empty ListValue", Unmarshaler{}, `{"lv": []}`, &pb.KnownTypes{Lv: &stpb.ListValue{}}},
 	{"basic ListValue", Unmarshaler{}, `{"lv": ["x", null, 3, true]}`, &pb.KnownTypes{Lv: &stpb.ListValue{Values: []*stpb.Value{
 		{Kind: &stpb.Value_StringValue{"x"}},
@@ -612,8 +612,17 @@ var unmarshalingTests = []struct {
 	{"BoolValue", Unmarshaler{}, `{"bool":true}`, &pb.KnownTypes{Bool: &wpb.BoolValue{Value: true}}},
 	{"StringValue", Unmarshaler{}, `{"str":"plush"}`, &pb.KnownTypes{Str: &wpb.StringValue{Value: "plush"}}},
 	{"BytesValue", Unmarshaler{}, `{"bytes":"d293"}`, &pb.KnownTypes{Bytes: &wpb.BytesValue{Value: []byte("wow")}}},
-	// `null` is also a permissible value. Let's just test one.
-	{"null DoubleValue", Unmarshaler{}, `{"dbl":null}`, &pb.KnownTypes{Dbl: &wpb.DoubleValue{}}},
+
+	// Ensure that `null` as a value ends up with a nil pointer instead of a [type]Value struct.
+	{"null DoubleValue", Unmarshaler{}, `{"dbl":null}`, &pb.KnownTypes{Dbl: nil}},
+	{"null FloatValue", Unmarshaler{}, `{"flt":null}`, &pb.KnownTypes{Flt: nil}},
+	{"null Int64Value", Unmarshaler{}, `{"i64":null}`, &pb.KnownTypes{I64: nil}},
+	{"null UInt64Value", Unmarshaler{}, `{"u64":null}`, &pb.KnownTypes{U64: nil}},
+	{"null Int32Value", Unmarshaler{}, `{"i32":null}`, &pb.KnownTypes{I32: nil}},
+	{"null UInt32Value", Unmarshaler{}, `{"u32":null}`, &pb.KnownTypes{U32: nil}},
+	{"null BoolValue", Unmarshaler{}, `{"bool":null}`, &pb.KnownTypes{Bool: nil}},
+	{"null StringValue", Unmarshaler{}, `{"str":null}`, &pb.KnownTypes{Str: nil}},
+	{"null BytesValue", Unmarshaler{}, `{"bytes":null}`, &pb.KnownTypes{Bytes: nil}},
 }
 
 func TestUnmarshaling(t *testing.T) {
@@ -756,4 +765,4 @@ func (m *dynamicMessage) MarshalJSONPB(jm *Marshaler) ([]byte, error) {
 func (m *dynamicMessage) UnmarshalJSONPB(jum *Unmarshaler, js []byte) error {
 	m.rawJson = string(js)
 	return nil
-}
+}