Dart built_Value, BuiltList error in serializer - Arguments of a constant creation must be constant expression

Question

I have the following json object

{
    "notifications": [
        {
            "correspondenceId": "81",
            "type": "notification",
            "title": "Find Your Future at Indiana University",
            "snippet": "",
            "readFlag": "NO",
            "date": "Delivered on: Jul 09, 2018 at 12:00 AM",
            "readDate": "Read on: Apr 03, 2018 at 12:00 AM",
            "icon": "message",
            "color": "neutral"
        },
        {
            "correspondenceId": "80",
            "type": "notification",
            "title": "My IU Experience",
            "snippet": "",
            "readFlag": "NO",
            "date": "Delivered on: Jul 09, 2018 at 12:00 AM",
            "readDate": "Read on: Apr 03, 2018 at 12:00 AM",
            "icon": "message",
            "color": "red"
        },
        {
            "correspondenceId": "82",
            "type": "notification",
            "title": "Test RSVP",
            "snippet": "",
            "readFlag": "NO",
            "date": "Delivered on: Jul 09, 2018 at 12:00 AM",
            "readDate": "Read on: Apr 10, 2018 at 04:31 PM",
            "icon": "message",
            "color": "neutral"
        }
    ]
}

I have created the following object model using built_value

import 'package:built_collection/built_collection.dart';
import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';

part 'notification.g.dart';

abstract class NotificationList
    implements Built<NotificationList, NotificationListBuilder> {
  BuiltList<NotificationElement> get notifications;

  NotificationList._();
  static Serializer<NotificationList> get serializer =>
      _$notificationListSerializer;
  factory NotificationList([updates(NotificationListBuilder b)]) =
      _$NotificationList;
}

abstract class NotificationElement
    implements Built<NotificationElement, NotificationElementBuilder> {
  String get correspondenceId;

  String get type;

  String get title;

  @nullable
  String get snippet;

  String get readFlag;

  bool get derivedReadFlag {
    return readFlag.contains("YES");
  }

  String get date;

  @nullable
  String get readDate;

  String get icon;

  String get color;

  NotificationElement._();
  static Serializer<NotificationElement> get serializer =>
      _$notificationElementSerializer;
  factory NotificationElement([updates(NotificationElementBuilder b)]) =
      _$NotificationElement;
}

And the following seralizer for json deserialization:

import 'package:built_value/serializer.dart';
import 'package:built_value/standard_json_plugin.dart';
import 'package:sunapsis/datasource/dataobjects/login.dart';
import 'package:sunapsis/datasource/dataobjects/notification.dart';

part 'serializers.g.dart';

@SerializersFor([
  Login,
  NotificationList,
])
final Serializers serializers =
    (_$serializers.toBuilder()..addPlugin(StandardJsonPlugin())).build();

The login object model worked fine and is working as expected but when I added the NotificationList to SerializersFor, the serializer.g.dart file started throwing errors. I am getting this error message for BuiltList in the serializers.g.dart file

Arguments of a constant creation must be constant expression

Invalid constant value

Undefined name 'BuiltList'

Undefined class 'ListBuilder'

On trying to compile I am getting this error which says the same thing

compiler message: lib/datasource/dataobjects/serializers.g.dart:24:15: Error: Getter not found: 'BuiltList'.
compiler message:               BuiltList, const [const FullType(NotificationElement)]),
compiler message:               ^
compiler message: lib/datasource/dataobjects/serializers.g.dart:25:21: Error: Method not found: 'ListBuilder'.
compiler message:           () => new ListBuilder<NotificationElement>()))
compiler message:                     ^^^^^^^^^^^

Not sure where I am going wrong or what the issue could be. Using the following versions for built_value and built_collection

built_value: "^5.5.3"
built_collection: "^3.1.1"
build_runner: ^0.8.0
built_value_generator: ^5.5.0

This is the serializer.g.dart file generated:

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'serializers.dart';

// **************************************************************************
// BuiltValueGenerator
// **************************************************************************

// ignore_for_file: always_put_control_body_on_new_line
// ignore_for_file: annotate_overrides
// ignore_for_file: avoid_annotating_with_dynamic
// ignore_for_file: avoid_returning_this
// ignore_for_file: omit_local_variable_types
// ignore_for_file: prefer_expression_function_bodies
// ignore_for_file: sort_constructors_first

Serializers _$serializers = (new Serializers().toBuilder()
      ..add(AuthProcess.serializer)
      ..add(Login.serializer)
      ..add(NotificationElement.serializer)
      ..add(NotificationList.serializer)
      ..addBuilderFactory(
          const FullType(
              BuiltList, const [const FullType(NotificationElement)]),
          () => new ListBuilder<NotificationElement>()))
    .build();

Any help will be greatly appreciated.

Answer 1

It looks like serializers.g.dart is missing an import for built_collection, which is where you find those type definitions. Add an import statement for it to serializers.dart (rather than the generated part file) and see if that does the trick.

Answer 2

In case that doesn't work! import

import 'package:built_collection/built_collection.dart';

In your serializers.dart It will reflect in serializers.g.dart