Add method to find extending interfaces of target interface

[Georgios Andrianakis]

I would like to be able to (efficiently) look up all the interfaces that extends a target interface.
Say for example that I have

public interface SomeInterface {

}

and there is an interface that extends is:

public interface SomeExtendingInterface extends SomeInterface {

}

Neither index.getAllKnownSubclasses() nor index.getAllKnownImplementors() covers the aforementioned usecase so I am forced do the following (inefficient) lookup:

    List<ClassInfo> getAllInterfacesExtending(DotName target, IndexView index) {
        List<ClassInfo> result = new ArrayList<>();
        Collection<ClassInfo> knownClasses = index.getKnownClasses();
        for (ClassInfo clazz : knownClasses) {
            if (!Modifier.isInterface(clazz.flags())) {
                continue;
            }
            List<DotName> interfaceNames = clazz.interfaceNames();
            boolean found = false;
            for (DotName interfaceName : interfaceNames) {
                if (interfaceName.equals(target)) {
                    found = true;
                    break;
                }
            }
            if (found) {
                result.add(clazz);
            }
        }
        return result;
    }

[Martin Kouba]

@Ladicek I think that this one would deserve your attention ;-)

[Ladislav Thon]

Good point, indeed neither getAllKnownSubclasses nor getAllKnownImplementors can be used for this. Adding something like getAllKnownSubinterfaces is certainly a good idea.

[Ladislav Thon]

Here's a funny thing: getKnownDirectImplementors returns direct subinterfaces, but getAllKnownImplementors doesn't return interfaces at all. This is inconsistent and counter-intuitive, but I hesitate to unify that. That would be a pretty serious behavioral breakage that can't be caught during compilation.

I still intend to add getKnownDirectSubinterfaces and getAllKnownSubinterfaces (actually working on that right now), but I'd welcome any opinions about the above.

[Georgios Andrianakis]

Sounds reasonable.

[Martin Kouba]

Hm, another funny thing: the javadoc of getAllKnownImplementors() was pretty clear that it only returns classes, not interfaces, but for some reason "interfaces" was replaced with "methodParameters" in 44d77cf#diff-cf6e0f736d92b7d69934c1308f902a9c5440c9075761997bc05a6bab7e0a5c6b. The same applies to getKnownDirectImplementors(). So it was intentional.

@n1hility can tell us more ;-).

[Ladislav Thon]

I don't think that methodParameters replacement was intentional, I'm fixing that as part of this work. (Thanks for pointing to the commit. I found a few more places that need fixing.)

I agree that it was intentional for getKnownDirectImplementors to return interfaces and getAllKnownImplementors to not return interfaces, I just find it very weird and unexpected. I feel a strong urge to fix that in one way or another, but I'm not exactly sure about it :-)

[Ladislav Thon]

I have an implementation over in #184. It doesn't change existing behavior, though I could be persuaded otherwise :-)

[Ladislav Thon]

Done in #184.