EventGroupProcessor does only execute the first registered handler for each event type

[Darkskald]

When running the example basic/5-cqrs-protobuf, using the group handlers (watermill v1.3.5, watermill-amqp/v2 v2.1.0)

	err = eventProcessor.AddHandlersGroup(
		"events",
		OrderBeerOnRoomBooked{commandBus},
		NewBookingsFinancialReport(),

		cqrs.NewGroupEventHandler(func(ctx context.Context, event *BeerOrdered) error {
			logger.Info("Beer ordered", watermill.LogFields{
				"room_id": event.RoomId,
			})
			return nil
		}),
	)

only the first handler for the RoomBooked event (OrderBeerOnRoomBooked) is executed, the output of the other handler is never visible. Upon interchanging them:

		NewBookingsFinancialReport(),
		OrderBeerOnRoomBooked{commandBus},

only the message from NewBookingsFinancialReport is displayed. From this observation I deduce that in the current implementation of EventGroupProcessors executes only the first handler for a specific event type and ignores all others.

[Darkskald]

I created a PR that should solve that issue, unfortunately I confused 403 and 402... sorry for that!

[MagdielCAS]

Any updates regarding this? 6 months later and it is still an issue, I spent some hours trying to figuring out why my code didn't work when it actually was the lib that returned after the first execution

[germainc]

Agree this would be a good change. The only workaround seems to be multiple handler groups but that can create a huge mess. If you have a domain with 10 events and need a second handler for 1 of them, you now have a group with 9 extra handlers returning nil just to ack messages. You can turn on AckOnUnknownEvent but that's a terrible idea since you have to turn it on for the entire processor.