Riverpod trigger rebuild when update state with freezed copywith even if nothing changed

Question

I thought Riverpod will only trigger rebuild if the state value is different but turn out it rebuild every time when state is set although the value is the same. Is that true?

The case is as below

@Freezed(genericArgumentFactories: true)
class Model with _$Model {
  const factory Model({required int id}) = _Model;
}

class Manager {
  static StateProvider<Model> modelProvider =
      StateProvider<Model>((ref) => Model(id: 1));
  Manager() {
    Stream.periodic(Duration(seconds: 1)).take(1000).listen((event) {
      ref.read(modelProvider.notifier).update((state) {
        var cloneState = state.copyWith();
        print("${state == cloneState}"); //This print true
        return cloneState;
      });
    });
  }
}

class TestWidget extends ConsumerWidget {
  const TestWidget();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    var model = ref.watch(Manager.modelProvider);
    print("model change......................"); //print every second
    return Text(model.id.toString());
  }
}

It showed that the TestWidget was rebuilt every seconds but I thought it shouldn't as the state is the same although I set it again. Am I missing something? Thanks.

Answer 1

Riverpod by default doesn't rely on == but identical to filter updates.
The reasoning is that == can be quite inefficient if your model becomes large.

But this causes the behavior you described: If two objects have the same content but use a different instance, listeners will be notified.
It's not considered a problem though, as there is no value in doing:

state = state.copyWith();