Bloc Concurrency with restartable transformer does not cancel previous event

Question

Description

Bloc Concurrency with restartable transformer does not cancel previous event

Steps To Reproduce

The bloc file merchant_product_bloc.dart that listen on an event MerchantProductCartChanged and emit the state MerchantProductCartChange

class MerchantProductBloc extends Bloc<MerchantProductEvent, MerchantProductState> {
  MerchantProductBloc() : super(MerchantProductInitial()) {
    on<MerchantProductCartChanged>(_changeCart, transformer: restartable());
  }

  Future<void> _changeCart(
    MerchantProductCartChanged event,
    Emitter<MerchantProductState> emit,
  ) async {
    await Future.delayed(const Duration(milliseconds: 300));
    logInfo('Cart Changed | productId=${event.productId} qty=${event.qty}');
    emit(const MerchantProductCartChange.loading());
    try {
      await productRepository.changeCart(
        productId: event.productId,
        qty: event.qty,
        date: event.date,
      );
      emit(const MerchantProductCartChange.success());
    } catch (e) {
      emit(MerchantProductCartChange.error(msg: e.toString(), lastData: event));
    }
  }
}

The button I used to trigger the event MerchantProductCartChanged

BlocProvider.of<MerchantProductBloc>(context).add(
  MerchantProductCartChanged(
    productId: product.id!,
    initialQty: 1,
  ),
);

When I pressed the button 4 times very fast. It logs 4 times as well and call API 4 times

I/PLogger (30516): {PAX A920}  {Loket}  {Cart Changed | productId=104 qty=13}  {06 May 2022 08:35:58 PM}  {INFO}
I/PLogger (30516): {PAX A920}  {Loket}  {Cart Changed | productId=104 qty=14}  {06 May 2022 08:35:58 PM}  {INFO}
I/PLogger (30516): {PAX A920}  {Loket}  {Cart Changed | productId=104 qty=15}  {06 May 2022 08:35:58 PM}  {INFO}
I/PLogger (30516): {PAX A920}  {Loket}  {Cart Changed | productId=104 qty=16}  {06 May 2022 08:35:58 PM}  {INFO}

Expected Behavior

Should only logs one line at last event

I/PLogger (30516): {PAX A920}  {Loket}  {Cart Changed | productId=104 qty=16}  {06 May 2022 08:35:58 PM}  {INFO}