I have just enabled K2 mode in IntelliJ. My spring boot project uses `kotlin-spring` plugin but now ...

# spring

[Robert Jaros]

I have just enabled K2 mode in IntelliJ. My spring boot project uses kotlin-spring plugin but now I'm seeing Classes annotated with '@Configuration' could be implicitly subclassed and must not be final errors for all my configuration classes. Is this a known issue?

[JasonB]

see that with @Transactional as well

[Riccardo Lippolis]

I don't have this issue, it seems to be working fine for me. Which versions are you using? I am using:

IntelliJ 2024.3
Kotlin 2.0.21
Spring Boot 3.3.5

[Robert Jaros]

I'm using the same versions (on Linux). Are you sure you have enabled K2 mode? Maybe you are using open classes?

[Riccardo Lippolis]

yes, K2 mode is enabled, and I am not using the open keyword

[Robert Jaros]

Strange :)

[Robert Jaros]

Do you use gradle or maven? And is your project Kotlin multiplatform or just Kotlin JVM?

[Riccardo Lippolis]

Gradle, Kotlin JVM project

[Riccardo Lippolis]

I am on Windows though, that's one difference 😅

[Robert Jaros]

It works fine for me with a different project which is Kotlin JVM.

[Robert Jaros]

So it's something with Kotlin multiplatform plugin.

[Robert Jaros]

@JasonB can you confirm you are using multiplatform plugin as well?

[Robert Jaros]

But what's even more strange, I don't have this problem in another multiplatform project (!).

[Robert Jaros]

The difference is the other project (without issue) uses spring boot plugin and kotlin mpp plugin together in one module, which is now a deprecated configuration. The problematic project uses a separate JVM module which applies the spring boot plugin (which is recommended solution now). But I have no idea how can this make a difference for IntelliJ?

[Robert Jaros]

But apparently it does make a difference. The problem is gone when I apply spring boot plugin to my main module.

[Robert Jaros]

Now I've removed the plugin and it still doesn't show errors 🙃

[Robert Jaros]

I think I can live with this workaround for now ... 😉

[JasonB]

I'm on OSX with a pure JVM project, once I turned off K2 and reimported Gradle, everything was fine

[Jakub Gwóźdź]

Hi. Has the solution to this issue been found? I have the exact same problem - as soon as I enabled K2 mode - boom headshot, everything's underscored in red

EDIT: Ok, while the gradle reloading didn't help, apparently the right workaround is to "close intellij and open again" 🙂