MapJsonObject: the JsonObjectSerializer serializer is not recognized

[danielgomezrico]

1. If I declare a field like: MapJsonObject it breaks saying:

MapJsonObject get payload;

Error:

type 'ListJsonObject' is not a subtype of type 'MapJsonObject' in type cast

Even If I declare the JsonObjectSerializer (like #1159) like this:

import 'package:built_value/src/json_object_serializer.dart';

final Serializers serializers = (_$serializers.toBuilder()
      ..add(JsonObjectSerializer())

2. If I declare the field like JsonObject it does not break, and internally it contains the proper MapJsonObject. It seems that the way to find the proper serializer uses

Expected

If I declare the Type like MapJsonObject it should work fine so everyone that use the model could know if it contains a list, a map or what.

Investigation

• It seems that the BuiltJsonSerializer use only the first type to find serializers:
  https://github.com/google/built_value.dart/blob/master/built_value/lib/src/built_json_serializers.dart#L53

• The JsonObjectSerializer contains all types here but since the other one just one the first one then it can not find the serializer for it:
  https://github.com/google/built_value.dart/blob/master/built_value/lib/src/json_object_serializer.dart#L12-L19

[davidmorgan]

Thanks for the issue report.

It never occurred to me that someone would want to do this :) but I agree it makes sense. I'll mark it as a feature request and see if there's some way to support it--next time I am working on built_value features. (I only do that every quarter or so).

[danielgomezrico]

It is one solution in order to be able to serialize/deserialize Map<String, dynamic> attributes, I haven't found another way