Support extending Freezed

[lirantzairi]

I'd like to use my own default Freezed annotation that has default parameter values (e.g toJson: true).
So Instead of:

import 'package:freezed_annotation/freezed_annotation.dart';

part 'my_model.freezed.dart';

@Freezed(toJson: true)
class MyModel with _$MyModel {
  const factory MyModel({
    required String name,
  }) = _MyModel;
}

I want:

import 'package:freezed_annotation/freezed_annotation.dart';

part 'my_model.freezed.dart';

class MyFreezed extends Freezed {
  const MyFreezed({
    super.unionKey,
    super.unionValueCase,
    super.fallbackUnion,
    super.copyWith,
    super.equal,
    super.toStringOverride,
    super.fromJson,
    super.toJson = true,
    super.map,
    super.when,
    super.makeCollectionsUnmodifiable,
    super.addImplicitFinal,
    super.genericArgumentFactories,
  });
}

@MyFreezed()
class MyModel with _$MyModel {
  const factory MyModel({
    required String name,
  }) = _MyModel;
}

Note that I don't want to create an instance of Freezed, instead I want to subclass Freezed so I can also set other parameters as needed.

The problem is that this crashes the build runner:

[SEVERE] freezed on lib/my_model.dart:

Null check operator used on a null value

Package versions:

• freezed_annotation: 2.4.1
• build_runner: 2.4.7
• freezed: 2.4.6

[rrousselGit]

Extending the annotation is not supported.

You can do:

const myFreezed = Freezed(toJson: true)