Kotlin Compiler Plugin doesn’t bind Java classes

[volo]

Describe the bug
Koin Compiler Plugin doesn’t generate a proper binding for Java classes

Consider the following class implementing an interface (the interface itself can be either in Java or Kotlin)

@Single
public class JavaImpl implements JavaInterface {

    private final LibraryRepositoryProtocol repository;

    @Inject
    public JavaImpl(LibraryRepositoryProtocol repository) {
        this.repository = repository;
    }
}

This results in the compilation error:

[Koin] Missing dependency: com.tezov.koin_sample.domain.protocol.JavaInterface
required by: com.tezov.koin_sample.domain.usecase.GetFavoriteLibrariesUseCase (parameter 'javaInterface')
in module: AppModule

If the implementation class JavaImpl is converted to Kotlin the issue is fixed and compilation succeeds.

To Reproduce
Steps to reproduce the behavior:

1. Check out https://github.com/volo-droid/koin-annotations-java-issue/tree/bug-with-koin-compiler
2. Try to compile it
3. See the compilation error:

   [Koin] Missing dependency: com.tezov.koin_sample.domain.protocol.JavaInterface
   required by: com.tezov.koin_sample.domain.usecase.GetFavoriteLibrariesUseCase (parameter 'javaInterface')
   in module: AppModule
   

Additional info
KSP also failed to generate a proper constructor binding for a Java class which has a non-default constructor. The class above results in the following generated code and compilation error No value passed for parameter 'repository':

single() { _ -> com.tezov.koin_sample.data.JavaImpl()} bind(com.tezov.koin_sample.domain.protocol.JavaInterface::class)

To Reproduce with KSP check out https://github.com/volo-droid/koin-annotations-java-issue/tree/bug-with-ksp

Expected behavior
Java classes should be picked up by Koin the same way as Kotlin are. If that's not possible, it should be mentioned in the documentation as a known limitation.

Koin project used and used version (please complete the following information):
koin-core version 4.2.0
koin-plugin version 0.4.1

[arnaudgiuliani]

Yeah, Java interfaces have not been tested.

[volo]

@arnaudgiuliani just to clarify, the issue is caused by Java classes, not Java interfaces. The interface can be either Java or Kotlin, as long as the implementation is in Kotlin it works well. Binding breaks (for both the Koin Compiler and older KSP plugin) only when the implementation class is in Java.

[volo]

Still reproducible with the latest Koin 4.2.1 and KCP 1.0.0-RC1 versions. The branch to reproduce it is here:
https://github.com/volo-droid/koin-annotations-java-issue/tree/bug-with-koin-compiler-1.0.0-RC1

[arnaudgiuliani]

Even Koin is not well-suited for Java. Need to see the gap to allow such integration