Freezed: Decorator issue with List<Object>

[bounty1342]

Hi,

Consider the following :

import 'package:flutter/material.dart';
import 'package:freezed_annotation/freezed_annotation.dart';
import 'package:flutter/foundation.dart';

import './converter/widgetList_converter.dart';

part 'testFreezed.freezed.dart';
part 'testFreezed.g.dart';

@freezed
abstract class Test2 with _$Test2 {
  const factory Test2({
    @ListWidgetModelConv() List<WidgetModel> widgets,
  }) = _Test2;

  factory Test2.fromJson(Map<String, dynamic> json) => _$Test2FromJson(json);
}

Generate :

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'testFreezed.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

_$_Test2 _$_$_Test2FromJson(Map<String, dynamic> json) {
  return _$_Test2(
    widgets: json['widgets'] as List,
  );
}

Map<String, dynamic> _$_$_Test2ToJson(_$_Test2 instance) {
  final val = <String, dynamic>{};

  void writeNotNull(String key, dynamic value) {
    if (value != null) {
      val[key] = value;
    }
  }

  writeNotNull('widgets', instance.widgets);
  return val;
}

Where with the corresponding Json_serialisable :

import 'package:flutter/material.dart';
import 'package:freezed_annotation/freezed_annotation.dart';
import 'package:flutter/foundation.dart';

import './converter/widgetList_converter.dart';

part 'test.g.dart';

@JsonSerializable(nullable: false)
class Test {
  Test({
    this.widgets,
  });

  factory Test.fromJson(Map<String, dynamic> json) => _$TestFromJson(json);
  Map<String, dynamic> toJson() => _$TestToJson(this);

  @ListWidgetModelConv()
  final List<WidgetModel> widgets;
}

Generate :

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'test.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

Test _$TestFromJson(Map<String, dynamic> json) {
  return Test(
    widgets: const ListWidgetModelConv()
        .fromJson(json['widgets'] as Map<String, dynamic>),
  );
}

Map<String, dynamic> _$TestToJson(Test instance) {
  final val = <String, dynamic>{};

  void writeNotNull(String key, dynamic value) {
    if (value != null) {
      val[key] = value;
    }
  }

  writeNotNull('widgets', const ListWidgetModelConv().toJson(instance.widgets));
  return val;
}

Could you have a look ?

[bounty1342]

By the way, replacing

@ListWidgetModelConv() List<WidgetModel> widgets,

by

@JsonKey(fromJson: fromJsons, toJson: toJsons) List<WidgetModel> widgets,

bypass it and produce expected result, but the decorator way should work.

Do we share the same opinion on this ?
Don't hesitate to let me know, if you need any thing else.

[rrousselGit]

What's ListWidgetModelConv?

[bounty1342]

It's a converter to handle serialisation/deserialisation :

import 'package:json_annotation/json_annotation.dart';

class ListWidgetModelConv
    implements JsonConverter<List<WidgetModel>, Map<String, dynamic>> {
  const ListWidgetModelConv();

  List<WidgetModel> fromJson(Map<String, dynamic> json) {
    if (json == null) {
      return <WidgetModel>[];
    }
    List<WidgetModel> result = <WidgetModel>[];
    for (String key in json.keys) {
      result.add(WidgetModel.fromJson(json[key]));
    }
    return result;
  }

  Map<String, dynamic> toJson(List<WidgetModel> object) {
    if (object == null) {
      return null;
    }
    Map<String, dynamic> result = <String, dynamic>{};
    object.asMap().forEach(
        (int key, WidgetModel val) => result[key.toString()] = val.toJson());

    return result;
  }
}

With type not in List, json_serialisable and Freezed get along just fine.

This converter for exemple, is handle properly:

import 'package:json_annotation/json_annotation.dart';

class DateTimeIntConv implements JsonConverter<DateTime, int> {
  const DateTimeIntConv();

  @override
  DateTime fromJson(int json) =>
      json == null ? null : DateTime.fromMillisecondsSinceEpoch(json);

  @override
  int toJson(DateTime object) =>
      object == null ? null : object.millisecondsSinceEpoch;
}

But looking at the freezed part, it seems, the type of the object from the list is smith to dynamic. By doing so, tthe converter don't match anymore. That's my 2 cents analysis.

[bounty1342]

I just try with

class ListWidgetModelConv
    implements JsonConverter<List<dynamic>, Map<String, dynamic>> {

it generate fine with :

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'testFreezed.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

_$_Test2 _$_$_Test2FromJson(Map<String, dynamic> json) {
  return _$_Test2(
    widgets: const ListWidgetModelConv()
        .fromJson(json['widgets'] as Map<String, dynamic>),
  );
}

Map<String, dynamic> _$_$_Test2ToJson(_$_Test2 instance) {
  final val = <String, dynamic>{};

  void writeNotNull(String key, dynamic value) {
    if (value != null) {
      val[key] = value;
    }
  }

  writeNotNull('widgets', const ListWidgetModelConv().toJson(instance.widgets));
  return val;
}

but my list contain only one type of object, so I presume I should be able to not to downcast it dynamic.

I'm I missing something ?

[rrousselGit]

What's WidgetModel?

[bounty1342]

It's an object of my project. Don't matter on the issue.

I you prefer, I could replace if with another common object, like Datetime, Color..

[bounty1342]

Ok, with DateTime it generate : List<DateTime> get datetime;

So I understand why you wanted to know what was WidgetModel. It's another class generated with Freezed.

[bounty1342]

@freezed
abstract class Container with _$Container {
  const factory Container.playlist({
    @required
        String name,
    )
       @ListWidgetModelConv()
        List<WidgetModel> currentWidgets,
  }) = PlayListModel;

  const factory EasivioContainer.widget({
    @required
        String name,
        @ListWidgetModelConv()
        List<WidgetModel> widgets,
  }) = WidgetModel;

  factory Container.fromJson(Map<String, dynamic> json) =>
      _$ContainerFromJson(json);
}

[rrousselGit]

It sounds like json_serializable is unable to access WidgetsModel for some reason

If you look in the file generated by, is "widgets" a List internally too?

[bounty1342]

inside container_model.freezed.dart found this :

@JsonSerializable()
class _$WidgetModel with DiagnosticableTreeMixin implements WidgetModel {
  const _$WidgetModel(
      {
      @required
          this.name,
      @ListWidgetModelConv()
          this.widgets,
      : assert(name != null),

  final List<dynamic> widgets;

So still a List but of dynamic instead of WidgetModel.

I wonder, if this is because, the object contain a list on himself, that the generation on the freezed part loose the type. (nope that work, related to Union then?)

[bounty1342]

Okay, sorry for disturbing you with Json_serialisable...

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:freezed_annotation/freezed_annotation.dart';

part 'test_model.freezed.dart';
part 'test_model.g.dart';

@freezed
abstract class TestModel with _$TestModel {
  const factory TestModel.model({
    List<Model> testModel,
  }) = Model;

  factory TestModel.fromJson(Map<String, dynamic> json) =>
      _$TestModelFromJson(json);
}

This simplified exemple is better.
List<Model> is converted to List<dynamic>

// GENERATED CODE - DO NOT MODIFY BY HAND
// ignore_for_file: deprecated_member_use_from_same_package, use_function_type_syntax_for_parameters, unnecessary_const, avoid_init_to_null, invalid_override_different_default_values_named

part of 'test_model.dart';

// **************************************************************************
// FreezedGenerator
// **************************************************************************

T _$identity<T>(T value) => value;
TestModel _$TestModelFromJson(Map<String, dynamic> json) {
  return Model.fromJson(json);
}

class _$TestModelTearOff {
  const _$TestModelTearOff();

  Model model({List<dynamic> testModel}) {
    return Model(
      testModel: testModel,
    );
  }
}

// ignore: unused_element
const $TestModel = _$TestModelTearOff();

mixin _$TestModel {
  List<dynamic> get testModel;

  Map<String, dynamic> toJson();
  $TestModelCopyWith<TestModel> get copyWith;
}

abstract class $TestModelCopyWith<$Res> {
  factory $TestModelCopyWith(TestModel value, $Res Function(TestModel) then) =
      _$TestModelCopyWithImpl<$Res>;
  $Res call({List<dynamic> testModel});
}

class _$TestModelCopyWithImpl<$Res> implements $TestModelCopyWith<$Res> {
  _$TestModelCopyWithImpl(this._value, this._then);

  final TestModel _value;
  // ignore: unused_field
  final $Res Function(TestModel) _then;

  @override
  $Res call({
    Object testModel = freezed,
  }) {
    return _then(_value.copyWith(
      testModel:
          testModel == freezed ? _value.testModel : testModel as List<dynamic>,
    ));
  }
}

abstract class $ModelCopyWith<$Res> implements $TestModelCopyWith<$Res> {
  factory $ModelCopyWith(Model value, $Res Function(Model) then) =
      _$ModelCopyWithImpl<$Res>;
  @override
  $Res call({List<dynamic> testModel});
}

class _$ModelCopyWithImpl<$Res> extends _$TestModelCopyWithImpl<$Res>
    implements $ModelCopyWith<$Res> {
  _$ModelCopyWithImpl(Model _value, $Res Function(Model) _then)
      : super(_value, (v) => _then(v as Model));

  @override
  Model get _value => super._value as Model;

  @override
  $Res call({
    Object testModel = freezed,
  }) {
    return _then(Model(
      testModel:
          testModel == freezed ? _value.testModel : testModel as List<dynamic>,
    ));
  }
}

@JsonSerializable()
class _$Model with DiagnosticableTreeMixin implements Model {
  const _$Model({this.testModel});

  factory _$Model.fromJson(Map<String, dynamic> json) =>
      _$_$ModelFromJson(json);

  @override
  final List<dynamic> testModel;

  @override
  String toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) {
    return 'TestModel.model(testModel: $testModel)';
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties
      ..add(DiagnosticsProperty('type', 'TestModel.model'))
      ..add(DiagnosticsProperty('testModel', testModel));
  }

  @override
  bool operator ==(dynamic other) {
    return identical(this, other) ||
        (other is Model &&
            (identical(other.testModel, testModel) ||
                const DeepCollectionEquality()
                    .equals(other.testModel, testModel)));
  }

  @override
  int get hashCode =>
      runtimeType.hashCode ^ const DeepCollectionEquality().hash(testModel);

  @override
  $ModelCopyWith<Model> get copyWith =>
      _$ModelCopyWithImpl<Model>(this, _$identity);

  @override
  Map<String, dynamic> toJson() {
    return _$_$ModelToJson(this);
  }
}

abstract class Model implements TestModel {
  const factory Model({List<dynamic> testModel}) = _$Model;

  factory Model.fromJson(Map<String, dynamic> json) = _$Model.fromJson;

  @override
  List<dynamic> get testModel;
  @override
  $ModelCopyWith<Model> get copyWith;
}

[rrousselGit]

Oh, so this is a recursive class

Instead of:

    List<Model> testModel,

do

    List<TestModel> testModel,

[bounty1342]

Still not quite, might have oversimplified the exemple :

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:freezed_annotation/freezed_annotation.dart';

part 'test_model.freezed.dart';
part 'test_model.g.dart';

@freezed
abstract class A with _$A {
  const factory A.b({
    String name,
    List<B> objectB,
  }) = B;

  const factory A.c({
    String name,
    List<C> objectC,
  }) = C;
}

I need to ensure C list doesn't contains B objects, but need the shared property to access the name.
Does my explanation make sense ?

[rrousselGit]

Why are both B and C under A?
Would it be logical to separate them?

@freezed
abstract class B with _$B {
  const factory B({
    String name,
    List<B> objectB,
  }} = _B;
}

@freezed
abstract class C with _$C {
  const factory C({
    String name,
    List<C> objectC,
  }} = _C;
}

[bounty1342]

B and C shared some properties. That's why I wanted to use the Union.
How would you write A then ?

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:freezed_annotation/freezed_annotation.dart';

part 'test_model.freezed.dart';
part 'test_model.g.dart';

@freezed
abstract class A with _$A {
  const factory A.b({
    String name,
    List<B> objectB,
  }) = _B;

  const factory A.c({
    String name,
    List<C> objectC,
  }) = _C;
}
@freezed
abstract class B with _$B {
  const factory B({
    String name,
    List<B> objectB,
  }} = _B;
}

@freezed
abstract class C with _$C {
  const factory C({
    String name,
    List<C> objectC,
  }} = _C;
}

Indeed, work well ! But is there a way not to repeat the entire class B and C in A ? (reason why I put them both in A and remove the private at the beginning to make them public)

[rrousselGit]

You could have:

@freezed
abstract class A with _$A {
  const factory A.b(B b) = _Ab;
  const factory A.c(C c) = _Ac;
}

@freezed
abstract class B with _$B {
  const factory B({
    String name,
    List<B> objectB,
  }} = _B;
}

@freezed
abstract class C with _$C {
  const factory C({
    String name,
    List<C> objectC,
  }} = _C;
}

[bounty1342]

But seems that I loose the shared properties on name field then.

I can't write A.name anymore.

[rrousselGit]

You can add it manually:

@freezed
abstract class A implements _$A {
  A._();
  factory A.b(B b) = _Ab;
  factory A.c(C c) = _Ac;

  String get name {
    return map(
      b: (b) => b.name,
      c: (c) => c.name,
    );
  }
}

[bounty1342]

Remy, thank you for taking the time.

But it's like redeclaring the model a second time. At least by copy pasting it, not DRY but easier to update.
Maybe that could be an evolution one day.

Until then feels like https://github.com/rrousselGit/freezed/issues/150#issuecomment-617080527 should work cause it takes advantage of the shared properties.
I replaced it manually in the generated file, and it compile, so wonder why it generate with dynamic instead of the real classe type.

Regards.

[rrousselGit]

Because during the step of analyzing the code you wrote to generate Model, then Model doesn't exist yet.

So List<Model> is interpreted as List<dynamic> by Dart's analysis server, and Freezed generated code in consequence

[bounty1342]

Run into https://github.com/rrousselGit/freezed/issues/142 with https://github.com/rrousselGit/freezed/issues/150#issuecomment-617106811

Will keep an eyes out for it, and give it another try later.
Thanks

[maks]

@bounty1342 once #204 lands it should help at least with the List having List in the freezed generated code.

[rrousselGit]

Since #204 is merged, is this still a problem?