The toJson method does not properly transform List<T> type parameters

[heronlyj]

The data type is the following

part of models.jsonc file:

[
    .........
    {
        "__className": "Course", // <- The base class name of the object.
        "type": 0,
        "name": "class name",
        "img": "image url",
        "id": 0,
        "courseNode": [
            {
                "type": 0,
                "level": 0,
                "sublevel": 0
            }
        ]
    }
]

Then the generated dart file looks like this (the toJson part)

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'course.dart';

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

_$_Course _$_$_CourseFromJson(Map<String, dynamic> json) {
  return _$_Course(
    type: json['type'] as int,
    name: json['name'] as String,
    img: json['img'],
    id: json['id'] as int,
    courseNode: (json['courseNode'] as List<dynamic>)
        .map((e) => CourseNode.fromJson(e as Map<String, dynamic>))
        .toList(),
  );
}

Map<String, dynamic> _$_$_CourseToJson(_$_Course instance) => <String, dynamic>{
      'type': instance.type,
      'name': instance.name,
      'img': instance.img,
      'id': instance.id,
      'courseNode': instance.courseNode,
    };

But the correct toJson code should look like this

Map<String, dynamic> _$_$_CourseToJson(_$_Course instance) => <String, dynamic>{
      'type': instance.type,
      'name': instance.name,
      'img': instance.img,
      'id': instance.id,
      'courseNode': instance.courseNode.map((e) => e.toJson()).toList(),
    };

---

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• No issues found!

  freezed_annotation: ^0.14.1
  json_annotation: ^4.0.1

dev_dependencies:
  flutter_test:
    sdk: flutter

  build_runner: ^1.12.2
  freezed: ^0.14.1+2
  json_serializable: ^4.1.0

vscode extension version: v3.1.1

[iamarnas]

@heronlyj Hi. Thank you for your report. I see you use json_serializable and I wonder have you same issues without json_serializable?

[heronlyj]

@iamarnas Hi.

If json_serializable is not referenced, thexxx.g.dart file will not be generated 😅

@heronlyj Hi. Thank you for your report. I see you use json_serializable and I wonder have you same issues without json_serializable?

[heronlyj]

@iamarnas Hi.

If don't use freezed, the result is the same, I mentioned the same issuse in

https://github.com/dart-lang/build/issues/3095

[iamarnas]

@heronlyj Hi.

If json_serializable is not referenced, the xxx.g.dart file will not be generated 😅

I meant that Json Serializable is false in your models.jsonc

Ok. Your generated JSON with Json to Dart Model looks as expected.

class Course {
  int type;
  String name;
  String img;
  int id;
  List<CourseNode> courseNode;

  Course({
    this.type,
    this.name,
    this.img,
    this.id,
    this.courseNode,
  });

  factory Course.fromJson(Map<String, dynamic> json) {
    return Course(
      type: json['type'] as int,
      name: json['name'] as String,
      img: json['img'] as String,
      id: json['id'] as int,
      courseNode: (json['courseNode'] as List<dynamic>)
          ?.map((e) => e == null
              ? null
              : CourseNode.fromJson(e as Map<String, dynamic>))
          ?.toList(),
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'type': type,
      'name': name,
      'img': img,
      'id': id,
      'courseNode': courseNode?.map((e) => e?.toJson())?.toList(),
    };
  }
}

When you use Freezed or Json Serializable then Json to Dart Model generates only types and everything that happens after Json Serializable takes care of the rest and is responsible for generated code. Even Freezed depends on Json Serializable. If Json Serializable fails then the Freezed fails too. So that in that case Json to Dart Model more accurate than Json Serializable :sunglasses: and I can do nothing here need wait for a fix from the Json Serializable developers and no reason to keep these issues opened.

[iamarnas]

But thanks to you @heronlyj I found where I missed syntax correction :smiley: From now on, generated code will be cleaner.

[iamarnas]

I'm closing this because issue are with json_serializable.