Flutter ferry custom scalar serializer "has non-dynamic type"

Question

I'm having a bit of a problem with a custom serializer in flutter ferry graphql package:

I have used exactly the example from the ferry docs: https://ferrygraphql.com/docs/custom-scalars/#create-a-custom-serializer

But I always get the following message when running the builder_runner:

[SEVERE] built_value_generator:built_value on lib/schema.schema.gql.dart:
Error in BuiltValueGenerator for abstract class GDailyForecastInput implements Built<GDailyForecastInput, dynamic>.
Please make the following changes to use BuiltValue:

1. Make field dateStart have non-dynamic type. If you are already specifying a type, please make sure the type is correctly imported.
2. Make field dateEnd have non-dynamic type. If you are already specifying a type, please make sure the type is correctly imported.
[SEVERE] built_value_generator:built_value on lib/schema.schema.gql.dart:
Error in BuiltValueGenerator for abstract class GHourlyForecastInput implements Built<GHourlyForecastInput, dynamic>.
Please make the following changes to use BuiltValue:

1. Make field dateStart have non-dynamic type. If you are already specifying a type, please make sure the type is correctly imported.
2. Make field dateEnd have non-dynamic type. If you are already specifying a type, please make sure the type is correctly imported.

dateStart and dateEnd are query input values of type Date This is my type overwrite: type_overrides: Date: name: Date Does anyone one why this error happens? I really can't find out what the problem is

Date is define das a scalar in my schema.graphql file:

"""A date string with format `Y-m-d`, e.g. `2011-05-23`."""
scalar Date

Here is my build.yaml file:

targets:
  $default:
    builders:
      gql_build|schema_builder:
        enabled: true
        options:
          type_overrides:
            Date:
              name: Date
              
      gql_build|ast_builder:
        enabled: true
        options:
          type_overrides:
            Date:
              name: Date

      gql_build|data_builder:
        enabled: true
        options:
          type_overrides:
            Date:
              name: Date
          schema: appdemo|lib/schema.graphql

      gql_build|var_builder:
        enabled: true
        options:
          type_overrides:
            Date:
              name: Date
          schema: appdemo|lib/schema.graphql

      gql_build|serializer_builder:
        enabled: true
        options:
          schema: appdemo|lib/schema.graphql
          custom_serializers:
            - import: './serializers/date_serializer.dart'
              name: DateSerializer

      ferry_generator|req_builder:
        enabled: true
        options:
          type_overrides:
            Date:
              name: Date
          schema: appdemo|lib/schema.graphql

I tried debugging already. If I rename my scalar to DateTime everything works fine. (I also have a scalar DateTime in my schema.graphql file.) It's only if I use the name Date that I get this error.

Am I missing something? Do I need to create additionally to the code in the documention a dart Date class and link it or so?

Answer 1

Make sure you also include type_overrides for data_builder, var_builder, and req_builder.

IMPORTANT We've included only the schema_builder above for brevity, but we will need to include this same type_overrides map for data_builder, var_builder, and req_builder as well. See the complete build.yaml example for more details.

For example:

Let's say I have two custom scalar, a primitive and a non-primitive type,

schema.graphql :

scalar Date #A datetime string in iso8601.
scalar Metadata #A map with key string and value any.

type Test {
  id: ID!
  date: Date!
  metadata: Metadata!
}

type Query {
  getTest(): Test!
}

date_serializer.dart :

import 'package:built_value/serializer.dart';

class DateSerializer implements PrimitiveSerializer<DateTime> {
  @override
  DateTime deserialize(
    Serializers serializers,
    Object serialized, {
    FullType specifiedType = FullType.unspecified,
  }) {
    assert(serialized is String,
        "DateSerializer expected 'String' but got ${serialized.runtimeType}");
    return DateTime.parse(serialized is String ? serialized : "");
  }

  @override
  Object serialize(
    Serializers serializers,
    DateTime date, {
    FullType specifiedType = FullType.unspecified,
  }) =>
      date.toUtc().toIso8601String();

  @override
  Iterable<Type> get types => [DateTime];

  @override
  String get wireName => "Date";
}

metadata_serializer.dart :

import "package:gql_code_builder/src/serializers/json_serializer.dart";

class MetadataSerializer extends JsonSerializer<Map<String, dynamic>> {
  @override
  Map<String, dynamic> fromJson(Map<String, dynamic> json) => json;

  @override
  Map<String, dynamic> toJson(Map<String, dynamic> map) => map;
}

build.yaml :

targets:
  $default:
    builders:
      gql_build|schema_builder:
        enabled: true
        options:
          type_overrides:
            Metadata:
              name: Map<String, dynamic>
            Date:
              name: DateTime
      gql_build|ast_builder:
        enabled: true

      gql_build|data_builder:
        enabled: true
        options:
          schema: my_project|lib/schema.graphql
          type_overrides:
            Metadata:
              name: Map<String, dynamic>
            Date:
              name: DateTime
      gql_build|var_builder:
        enabled: true
        options:
          schema: my_project|lib/schema.graphql
          type_overrides:
            Metadata:
              name: Map<String, dynamic>
            Date:
              name: DateTime
      gql_build|serializer_builder:
        enabled: true
        options:
          schema: my_project|lib/schema.graphql
          custom_serializers:
            - import: 'path/to/metadata_serializer.dart'
              name: MetadataSerializer
            - import: 'path/to/date_serializer.dart'
              name: DateSerializer

      ferry_generator|req_builder:
        enabled: true
        options:
          schema: my_project|lib/schema.graphql
          type_overrides:
            Metadata:
              name: Map<String, dynamic>
            Date:
              name: DateTime

After build you should now have both scalar overridden,

test.dart :

client.request(request).first.then((response){
  print(response.data?.test.date.runtimeType);
  print(response.data?.test.metadata.runtimeType);
})

output :

DateTime
JsLinkedHashMap<String, dynamic>