feat: add MarshalSlice

Signed-off-by: Christian Stewart <[email protected]>

json/marshal.go

@@ -60,6 +60,24 @@ func (c MarshalerConfig) Marshal(m Marshaler) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+// MarshalSlice marshals a slice of Marshalers into a JSON array.
+func (c MarshalerConfig) MarshalSlice(ms []Marshaler) ([]byte, error) {
+	var buf bytes.Buffer
+	s := NewMarshalState(c, NewJsonStream(&buf))
+	s.WriteArrayStart()
+	for i, m := range ms {
+		if i > 0 {
+			s.WriteMore()
+		}
+		m.MarshalProtoJSON(s)
+	}
+	s.WriteArrayEnd()
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
 // MarshalState is the internal state of the Marshaler.
 type MarshalState struct {
 	inner  *JsonStream

json/marshal_test.go

@@ -178,3 +178,35 @@ func TestMarshaler(t *testing.T) {
 	testMarshal(t, func(s *MarshalState) { s.WriteDuration(testDuration.Truncate(100000000)) }, `"3723.100s"`)
 	testMarshal(t, func(s *MarshalState) { s.WriteDuration(testDuration.Truncate(1000000000)) }, `"3723s"`)
 }
+
+type testMarshaler struct {
+	value int
+}
+
+func (m *testMarshaler) MarshalProtoJSON(s *MarshalState) {
+	s.WriteObjectStart()
+	s.WriteObjectField("value")
+	s.WriteInt32(int32(m.value))
+	s.WriteObjectEnd()
+}
+
+func TestMarshalSlice(t *testing.T) {
+	testSlice := []Marshaler{
+		&testMarshaler{value: 1},
+		&testMarshaler{value: 2},
+		&testMarshaler{value: 3},
+	}
+
+	expected := `[{"value":1},{"value":2},{"value":3}]`
+
+	config := DefaultMarshalerConfig
+
+	result, err := config.MarshalSlice(testSlice)
+	if err != nil {
+		t.Errorf("MarshalSlice returned an error: %v", err)
+	}
+
+	if string(result) != expected {
+		t.Errorf("MarshalSlice result does not match expected.\nGot:      %s\nExpected: %s", string(result), expected)
+	}
+}