In Hexagonal Architecture, can a UseCase call another UseCase?

Question

My layers are like:

Controller (Http) -> Use Case -> Domain Services

Imagine that I have a PurchaseController which is just getting the parameters from the Http Request and calling the PurchaseUseCase.

This PurchaseUseCase is using some domain services (like an OrderRepository, etc)

But, it needs also to get information or deal with another context.

Is it ok, for example, call the GetUserInfoUseCase (it's in another context, and I feel coupling context), from the PurchaseUseCase? Or should I use a Domain Service (for example a UserInfoProviderService) from a shared kernel?

In resume, the question is, can a UseCase call another UseCase (from another context)

If it would be an action that I can fire and forget, I would use an event and listen to it from the other context. But it's not the case, in this case, I need to retrieve some data from the other context or validate some info (like if the user has enough money, whatever)

Answer 1

Reading the whole text of the question, title should be: "Can my use case implementation call a use case of another remote application (hexagon)?" The answer is yes. You should create a driven port for that. The driven adapter would do the remote call.

Answer 2

From your question, it is clear that the functionalities belong in separate bounded contexts. So the straightforward answer would be No, you shouldn't.

It is good to assume that someday in the future, given sufficient scale and performance requirements, each bounded context will become a Microservice of its own.

So if you want to use some functionality in another context, you would generally access it via a well-published API, like a method in an Application Service, an API, async over a Messaging Medium, etc.