if I'd like to retrieve all the classes marked with a specific annotation, shall I use the kotlinx.serialization for that (for the descriptor)?

Are you talking some kind of multiplatform reflection?

yep

kotlinx.serialization uses findAssociatedObject

I wonder if I can exploit, at runtime, the descriptor generated at compile time

The descriptor is in the companion object, I don't think you can enumerate those

that

findAssociatedObject

looks to be only native and js?

On the JVM you can use plain reflection/classpath scanning I guess?

so I need 2 implementations 😕

yep

yeah, someone mentioned that, but I have no idea where to start

KSP isn't that hard, calling

resolver.getSymbolsWithAnnotation()

will get you all your classes. Then use KotlinPoet to generate a top level list of all of them

I need that at runtime

Ah oh yea then KSP won't help

what if I use KSP for getting all classes with the annotation I want, generating at compile time some metadata to be read in runtime later on?

Yep, this is exactly what I was suggesting

I'd need the list of all the classes, in third dependencies too.. do you think it'll work?

Yep, KSP scans the compile classpaths of your sources

eh, the problem is on native, there is no classpath over there

I would expect this to work

this is a library, do you think this will work on consumers side as well?

If your users add the KSP processor to their build, sure