[gql_build] ensure all serializer return types (all types?) are available in generated file, or allow import config

[danielmahon]

@smkhalsa Issue created from our DIscord discussion

A custom serializer's return type that is imported from another file is not shown in serializers.gql.dart causing a build error.

Only happens with generated BuiltLists? I have other custom scalars set-up the same way but addBuilderFactory functions are not generated for them so this problem doesn't occur...

Also, the addBuilderFactory function is generated multiple times...

Note: build_runner build is still successful

Error

lib/graphql/schema/serializers.gql.g.dart:182:59: Error: Getter not found: 'MyModel'.
          const FullType(BuiltList, const [const FullType(MyModel)]),
                                                          ^^^^^^^^^^^^^^
lib/graphql/schema/serializers.gql.g.dart:183:33: Error: 'MyModel' isn't a type.
          () => new ListBuilder<MyModel>())
                                ^^^^^^^^^^^^^^

Example

# schema.g.graphql
#...
"""JSON encoded custom scalar type"""
scalar MyModelPlural

type Foo {
  id: String!
  items: [MyModelPlural!]
}
#...

# build.yaml
#...
      ferry_generator|req_builder:
        enabled: true
        options:
          schema: flutter_app|lib/graphql/schema/schema.g.graphql
          type_overrides:
            MyModelsPlural:
              name: MyModel
              import: 'package:flutter_app/models/my_model.dart'
      gql_build|serializer_builder:
        enabled: true
        options:
          schema: flutter_app|lib/graphql/schema/schema.g.graphql
          custom_serializers:
            - import: 'package:flutter_app/graphql/serializers/my_model_serializer.dart'
              name: MyModelSerializer
#...

// my_model_serializer.dart

// ignore: implementation_imports
import 'package:gql_code_builder/src/serializers/json_serializer.dart';

// This import exposes "MyModel" which will be required, but missing, from serializers.gql.dart
import 'package:flutter_app/models/my_model.dart';

class MyModelSerializer extends JsonSerializer<MyModel> {
  @override
  MyModel fromJson(Map<String, dynamic> data) {
    return MyModel.fromJson(data);
  }
  @override
  Map<String, dynamic> toJson(MyModel model) {
    return model.toJson();
  }
}

// serializers.gql.dart

//...
// Correctly exposes "MyModelSerializer" but NOT "MyModel", causing built file to have missing type
import 'package:flutter_app/graphql/serializers/my_model_serializer.dart'
    show MyModelSerializer;

part 'serializers.gql.g.dart';

final SerializersBuilder _serializersBuilder = _$serializers.toBuilder()
  ..add(OtherSerializer())
  ..add(MyModelSerializer())
//...

// serializers.gql.g.dart

//...
      ..addBuilderFactory(
          const FullType(BuiltList, const [const FullType(MyModel)]),
          () => new ListBuilder<MyModel>()))
      ..addBuilderFactory(
          const FullType(BuiltList, const [const FullType(MyModel)]),
          () => new ListBuilder<MyModel>()))
     ..addBuilderFactory(
          const FullType(BuiltList, const [const FullType(MyModel)]),
          () => new ListBuilder<MyModel>()))
//...

[danielmahon]

adding the missing import MyModel into serializers.gql.dart fixes the issue, but I still haven't dug deep enough into built_value to see why/where it's adding those builder factories, and why it's only doing it for the list item and not the other overrides

[smkhalsa]

@danielmahon built_value generates the serializers.gql.g.dart file based on the contents of your serializers.gql.dart.

I don't actually think this has anything to do with the custom serializer. built_value is building the BuilderFactories because one of your GraphQL operations uses a BuiltList<MyModel>, and BuilderFactories are what tell built_value how to serialize BuiltLists of non-standard types.

The easiest solution would be to just include an import of any type overrides by default. I've created PR #148 which implements this. Can you please confirm that it fixes the issue? NOTE: you will need to include your type_overrides map in the serializer_builder in your build.yaml file.

A more elegant solution that selectively imports the custom types only when they will be used in a BuilderFactory would not be trivial, and I think this solution is probably good enough.

[danielmahon]

@smkhalsa this works, thank you