I’m currently in a process of migration to Kotlin 2.0 in my project. I’ve followed the `Anvil` part ...

# squarelibraries

[ilyagulya]

I’m currently in a process of migration to Kotlin 2.0 in my project.
I’ve followed the Anvil part of @Zac Sweers post (interface merging part as well): https://www.zacsweers.dev/preparing-for-k2/
However, I’m getting a compilation error suggesting that interface merging was not in fact done:

Type mismatch: inferred type is ScreenComponent but UserDocumentsDependencies was expected
Type mismatch: inferred type is ScreenComponent but CatalogDependencies was expected
... etc

What is a proper way to debug this situation?

[Zac Sweers]

This is pretty limited information and it’s hard to advise without more details

[ilyagulya]

@Zac Sweers I’m sorry.
I’m using Anvil 2.5.0-beta09
Gradle 8.7
Kotlin 2.0.0

Here’s all my build configuration (several convention plugins as well as build configuration for library module which contains ScreenComponent), example of how ScreenComponent and (for instance) contributed UserDocumentDependencies looks like.
https://gist.github.com/IlyaGulya/2b53e49ccc856a135dea065cdf179bd8

I’ve tried to attach a debugger to Gradle.
IrContributionMerger seems to be registered:

IrGenerationExtension.registerExtension(
  project,
  IrContributionMerger(scanner, moduleDescriptorFactory),
)

But IrContributionMerger.generate method never being called for some reason.

[ilyagulya]

Above error happens when I’m trying to assign ScreenComponent to contributed interface’s lateinit var instance inside its companion object

[Zac Sweers]

🤔 that’s surprising that the merger isn’t called. In the stub gen task or the compilation task? The latter is what would affect your runtime cast

[ilyagulya]

It’s not called nor in the stub gen task, neither in compilation task 😅
My breakpoint in the AnvilComponentRegistrar stops only in the compilation task, btw.

[ilyagulya]

@Zac Sweers The latter is what would affect your runtime cast - that’s not runtime issue, but compile-time one.

[Zac Sweers]

can you paste a full stacktrace?

[ilyagulya]

Untitled

Untitled

[ilyagulya]

Here’s a stacktrace from gradle as a snippet above, if it helps.
That’s a regular compilation error, not an exception:

> Task :apps:base:store:compileInternalDebugKotlin FAILED
e: file:///Users/ilyagulya/Projects/Qantor/qa-android-apps/apps/base/store/src/main/java/ru/qantor/customer/presentation/CustomerApp.kt:155:54 Type mismatch: inferred type is ScreenComponent but UserDocumentsDependencies was expected
e: file:///Users/ilyagulya/Projects/Qantor/qa-android-apps/apps/base/store/src/main/java/ru/qantor/customer/presentation/CustomerApp.kt:156:48 Type mismatch: inferred type is ScreenComponent but CatalogDependencies was expected
e: file:///Users/ilyagulya/Projects/Qantor/qa-android-apps/apps/base/store/src/main/java/ru/qantor/customer/presentation/CustomerApp.kt:157:50 Type mismatch: inferred type is ScreenComponent but FavoritesDependencies was expected
e: file:///Users/ilyagulya/Projects/Qantor/qa-android-apps/apps/base/store/src/main/java/ru/qantor/customer/presentation/CustomerApp.kt:158:57 Type mismatch: inferred type is ScreenComponent but PersonalManagersDependencies was expected
e: file:///Users/ilyagulya/Projects/Qantor/qa-android-apps/apps/base/store/src/main/java/ru/qantor/customer/presentation/CustomerApp.kt:159:49 Type mismatch: inferred type is ScreenComponent but MarkdownDependencies was expected
e: file:///Users/ilyagulya/Projects/Qantor/qa-android-apps/apps/base/store/src/main/java/ru/qantor/customer/presentation/CustomerApp.kt:160:47 Type mismatch: inferred type is ScreenComponent but EventsDependencies was expected

[ilyagulya]

IrContributionMerger.generate seems to be called in the modules with such configuration:

anvil {
    useKsp(contributesAndFactoryGeneration = true)
    generateDaggerFactories = true
}

But not in ones where I fallback Kapt and KotlinCompile tasks languageVersion to 1.9

[Zac Sweers]

that seems surprising, contribution merging should never run at the same time as dagger factory generation as you’d end up with duplicate classes

[Zac Sweers]

are you able to put together a minimal repro?

[ilyagulya]

I will try tomorrow 🙂

[ilyagulya]

@Zac Sweers ok, I couldn’t wait and made a reproducer 🙂
https://github.com/IlyaGulya/AnvilInterfaceMerginIssueSample

You can try to run MainKt in :entrypoint module and see the error:
Type mismatch: inferred type is SomeComponent! but Dependencies was expected

[ilyagulya]

@Zac Sweers hi!
I’ve made some research regarding this issue.
Apparently interface merging does not work in k1 because there’s no previously present SyntheticResolveExtension which were deleted in these commit.
https://github.com/square/anvil/commit/c35bef587974c432371fffebb610122ccb96d89b

This happens because IR generation is running after analysis, and analysis fails because of absense of SyntheticResolveException.
I’ve just checked that returning SyntheticResolveExtension back fixes the issue.
I’m not sure what is the correct way to provide analyzer information about the supertypes which will be merged in the IR generation phase.
I’ve just checked the Parcelize plugin and it seems to use SyntheticResolveExtension as well for this purpose.
Are you sure that it’s no longer required?

Seems that it should be preserved for K1 (I’m assuming this according to this message https://kotlinlang.slack.com/archives/C7L3JB43G/p1709191343204389?thread_ts=1709191090.501719&cid=C7L3JB43G)

[Zac Sweers]

We reimplemented it in IR instead, that’s why it’s deleted there

[Zac Sweers]

It works on K1 but not K2

[ilyagulya]

But IR implementation is not enough to provide the analyzer all required info.
I suppose that this is also the case for K2 and there will be required a FirDeclarationGenerationExtension as well

[Zac Sweers]

the sad news is that IR isn’t viable long term anyway

[Zac Sweers]

I’ve already talked with compiler folks about this, and the TL;DR is that we cannot rely on modifying supertypes during IR generation

[Zac Sweers]

so we will need to do something different, likely generating a new merged component class and making the root one extend it

[Zac Sweers]

I have started this work in Anvil, but I’m limited by reviews

[Zac Sweers]

that new one is implemented in KSP

[ilyagulya]

I see. Just checked the ksp implementation and I'm not quite sure how are you going to implement the interface merging without FIR or IR transformations? What do you mean by "making the root one extend it"?
I hope I'm not wasting your time by this questions 😅

[Zac Sweers]

we can’t modify sources

[Zac Sweers]

so the KSP implementation will generate a new class

[Zac Sweers]

and the original source impl will just need to manually extend it

[Zac Sweers]

or users will need to reference the generated component

[Zac Sweers]

more likely going to be the latter in the end

[Zac Sweers]

where we generate an API that looks like dagger’s, but it will call through an internal intermediary merged component we generated

[ilyagulya]

Oh, I see

[ilyagulya]

Thanks for explanation!
Do you need any help?

[Zac Sweers]

No I just need reviews from the square side