Query handler breaking the dependency rule?

[thatguysimon]

Hi @Sairyss!
Thanks for this awesome repo! It's been super helpful. I did encounter an issue recently though -

According to the readme - queries should be part of the application layer. But when looking at find-users.query-handler.ts, we can see it's importing dependencies from an outer layer - the infrastructure layer (like slonik and user.repository).

Doesn't that break the dependency rule? Or am I missing something?
If queries are at the same layer as application services, shouldn't they be required to use ports to communicate to "the outside world" just like application services are required to?

Thanks!
Simon

[Sairyss]

Good catch.
In a previous version of the application I was using repositories in queries to make a clear separation, but according to this discussion and this blogpost I simplified queries to be better aligned with CQRS principles. Since queries are just a read operation of the database and we don't execute any business logic here, I don't see much sense abstracting them with interfaces when using CQRS. In theory this violates the dependency rule, but on practice it's less boilerplate code. Alternatively you could separate this 1 class into 2 if you have a need for it

[thatguysimon]

@Sairyss I'm concerned about a linter we use to block us from breaking the dependency rule.
What do you think of placing queries in the infrastructure layer? This way we never leave it.
Controller -> QueryHandler -> Repo (or Raw SQL)
Now all components are part of the infrastructure layer so we stay within that layer through the entire request.

Also, regarding your alternative - how would you suggest to split it?

[Sairyss]

You can leave query handlers in application layer, but move slonik and SQL query strings into a separate adapter/repo class and inject it into query handlers (same principle as for example in create-user.service.ts ). or as you mentioned you can place queries in the infrastructure layer. Depends what you like more

[thatguysimon]

Got it, thanks!