EventBus and @EventHandler decorator about cqrs

[kamilmysliwiec]

Could you please provide a minimal repository which reproduces your issue?

[FERNman]

Hi @kamilmysliwiec ,

I'm currently experiencing the same problem as @JulienKyu. What he meant by his issue is that when two modules have an event handler with the same name, the DI token for both is the same. Therefore only the one registered first will be called, but twice.

I suppose this is something more people are experiencing because it is common to name event handlers by the events they are handling.

Here is a reproduction: https://stackblitz.com/edit/nest-duplicate-event-handlers-reproduction

Although I'm not that deep into the NestJS DI system, I guess it should be possible to scope the event handlers in the ExplorerService to their module.

For everyone else stumbling across this: I'm currently using the same workaround as per the original issue, just prefixing all event handlers with the module name.

[imxm]

is it fixed, because I am having the same issue?

[JulienKyu]

Could you please provide a minimal repository which reproduces your issue?

Yes I can, I wait just weekend to do this. Thanks

[JulienKyu]

@FERNman

To fix temporary this issue I use a custom class named "Projection" with @EventsHandler(...) and this method.

public getEventHandler<E extends IEvent>(event: E): IEventHandler<E> {
    const eventHandlerName = event.type + 'Handler';
    try {
        return this.moduleRef.get(eventHandlerName);
    } catch (e) {
        this.logger.error(eventHandlerName + ' not implemented');
    }
}

I have also register all EventHandler named by the event name followed EventHandler suffix.

With this strategy, I can use each event handler as same name for same event splitted by module.

Dont forget to add type property to all events like this:

....
public type: string;

public constructor() {
    this.type = this.constructor.name;
}
....

[JulienKyu]

@kamilmysliwiec

Could you please provide a minimal repository which reproduces your issue?

Here is a reproduction: https://github.com/FERNman/nest-duplicate-event-handler

Could you please re open this issue ? or you want I create another issue ?

Thanks a lot

[JulienKyu]

Hi,

I dont think it's fixed,

examples of simple interest to illustrate the motivation:

Domain (Module)
-Pricing
--OrderCreatedEventHandler
---Update some price
-ProductCatalog
--OrderCreatedEventHandler
---Update inventory

For now, I have not found better method than this to make this example work, with official documentation code sample, OrderCreatedEvent has handle 2 times by first handler named OrderCreatedEventHandler in the module Domain.

@kamilmysliwiec please help us

Thanks a lot

[kobyzskyi]

Any updates with it? I have the same issue. Version of CQRS package - 8.0.0

[IRCraziestTaxi]

I just ran into (I think) the same problem with this. I have two different queries (classes that are the argument for two different @QueryHandlers) in two different modules, but the incorrect query handler was being used for the query I was calling via the query bus. I double checked that all my imports were correct; that is, the query/handler from the incorrect module was not being imported, but rather the one local to the module. Changing the name of one of the query classes fixed the issue. It does seem like a bug to me.