RESTEasy Reactive: UniInvoker signatures are wrong

[FroMage]

Due to how we implement it, all its return types are Uni<?> instead of the more useful Uni<R> for methods like <R> get(Class<R>), forcing users to cast the return types to the right type:

UniInvoker invocation = target.request().rx(UniInvoker.class);
Uni<String> ret = (Uni<String>) invocation.get(String.class);

This is because we implemented it with:

public class UniInvoker extends AbstractRxInvoker<Uni<?>> {}
...
public abstract class AbstractRxInvoker<T> implements RxInvoker<T> {

    @Override
    public <R> T get(Class<R> responseType) {
        return method("GET", responseType);
    }
}

Now, for some reason the JAXRS interface is:

public interface RxInvoker<T> {

    public <R> T get(Class<R> responseType);
}

Which is pretty useless. We could mitigate this by making UniInvoker generic.

Or we could do like for MultiInvoker (for some reason this does pass the Java type system):

public class MultiInvoker extends AbstractRxInvoker<Multi<?>> {

    @SuppressWarnings("unchecked")
    @Override
    public <R> Multi<R> get(Class<R> responseType) {
        return (Multi<R>) super.get(responseType);
    }
}

Perhaps we should do both (generify and fix the signature via that weirdly allowed covariant override)?

[quarkus-bot]

/cc @geoand, @stuartwdouglas

[FroMage]

Huh, CompletionStageRxInvoker does the same trick to fix the signature of <R> get(Class<R>):

public interface CompletionStageRxInvoker extends RxInvoker<CompletionStage> {

    @Override
    public CompletionStage<Response> get();

    @Override
    public <T> CompletionStage<T> get(Class<T> responseType);

But interestingly it also overrides get() to return a CompletionStage<Response> which is probably what we should do too?

[geoand]

But interestingly it also overrides get() to return a CompletionStage<Response> which is probably what we should do too?

That does sounds reasonable