KSP Incremental Compilation Failure If Module Class is Generated by Another Non-Dirtied Processor

[sam-step]

I have a simple KSP processor which generates a Dagger Module. When using Dagger with KSP, incremental compilation fails if the input source of that generated Module is not dirtied.

E.g. given:

package app

@TargetAnnotation
class AnnotatedClass

and the following Module generated by a KSP processor:

package app.generated

// Output is non-aggregating, declares AnnotatedClass as source file.
@dagger.Module
class Generated_AnnotatedClassModule {
    @dagger.Provides
    fun provide(): app.ClassProvidedByGeneratedModule = app.ClassProvidedByGeneratedModule()
}

which is installed in a component:

package app

@Component(modules = [app.generated.Generated_AnnotatedClassModule::class])
interface MyComponent {
    fun classProvidedByGeneratedModule(): ClassProvidedByGeneratedModule
    fun otherClass(): OtherClass
}

making a change to, say, OtherClass, cause the incremental compilation to fail because the Dagger compiler cannot see Generated_AnnotatedClassModule:

> Task :app:kspKotlin FAILED
e: [ksp] ComponentProcessingStep was unable to process 'app.MyComponent' because 'generated.Generated_AnnotatedClassModule' could not be resolved.

Dependency trace:
    => element (INTERFACE): app.MyComponent
    => annotation type: dagger.Component
    => annotation: @dagger.Component(modules={generated.Generated_AnnotatedClassModule}, dependencies={})
    => annotation value (TYPE_ARRAY): modules={generated.Generated_AnnotatedClassModule}
    => annotation value (TYPE): modules=generated.Generated_AnnotatedClassModule
    => type (ERROR annotation value type): generated.Generated_AnnotatedClassModule

If type 'generated.Generated_AnnotatedClassModule' is a generated type, check above for compilation errors that may have prevented the type from being generated. Otherwise, ensure that type 'generated.Generated_AnnotatedClassModule' is on your classpath.
4 actionable tasks: 1 executed, 3 up-to-date

My assumption is that because the Generated_AnnotatedClassModule is not declared as a source to any of the files generated by Dagger, KSP doesn't bother making it available on incremental compilation. (Playing around with a couple sample processors in a reproducer project, I see this is the case. If I have two processors A and B: A generates a class that B needs to resolve in some way to generate its own class, upon incremental compilation where A's class is not dirtied, B won't see the class A generated unless it declared it as a source to its output on the original compilation).

I'm not sure if this is an issue with Dagger, with KSP, or a misunderstanding of expectations on my part here.

I have a minimal project demonstrating the above here: https://github.com/sam-step/dagger-ksp-incremental-repro

[bcorso]

Thanks for posting! I think this is a KSP issue, so I've filed it here google/ksp#2536.