check-is-not-closed-after-async-gap

added in: 1.4.0

Warns when an async handler does not have isClosed check before dispatching an event after an async gap.

Example

❌ Bad:

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterIncrementEvent>(_handle);
    on<CounterDecrementEvent>((event, emit) async {
      emit(state + 1);
      await Future.delayed(const Duration(seconds: 3));
      add(CounterDecrementEvent()); // LINT
    });
  }

  Future<void> _handle(CounterEvent event, Emitter<int> emit) async {
    emit(state + 1);
    await Future.delayed(const Duration(seconds: 3));
    emit(CounterDecrementEvent()); // LINT
  }
}

✅ Good:

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterIncrementEvent>(_handle);
    on<CounterDecrementEvent>((event, emit) async {
      emit(state + 1);
      await Future.delayed(const Duration(seconds: 3));
      if (!isClosed) {
        add(CounterDecrementEvent());
      }
    });
  }

  Future<void> _handle(CounterEvent event, Emitter<int> emit) async {
    emit(state + 1);
    await Future.delayed(const Duration(seconds: 3));
    if (!isClosed) {
      emit(CounterDecrementEvent());
    }
  }
}

Example​

Example