KSP errors are not included in the message output

[ansman]

I'm trying to use errors printed by KSP in my test but it seems that any KSP logs are not included. I see them in the test logs but not in KotlinCompilation.Result.messages.

[evant]

It's because the stderror stream isn't captured. Was able to work around this by capturing the stderr stream myself. https://github.com/evant/kotlin-inject/blob/main/compiler-tests/src/main/kotlin/me/tatarka/inject/ProjectCompiler.kt#L31

[ZacSweers]

I've got a slightly different hack via just copying the sources (leftover from when I needed a newer version compatible with the new package names): https://github.com/ZacSweers/MoshiX/blob/main/ksp-test-util/src/main/kotlin/com/tschuchort/compiletesting/symbolProcessors.kt#L94-L98

@tschuchortdev do you have an implementation in mind for this TODO item in Ksp.kt?

https://github.com/tschuchortdev/kotlin-compile-testing/blob/master/ksp/src/main/kotlin/com/tschuchort/compiletesting/Ksp.kt#L121

If so I'd be happy to take a look at a PR!

[tschuchortdev]

@ZacSweers I don't have a specific implementation in mind. The whole KSP implementation is kind of hacky, because kotlin-compile-testing is not very composable right now, so you might not find a "clean" way to access the KotlinCompilation.messageOutputStream. Currently my plan is to gather complaints/use cases for now and then rewrite it (in December maybe) to be more composable when I have a better grasp of the requirements. Since this will break API compatibility I don't want to rush it and have to rewrite again in the future.

You can try one of the following approaches:

• Maybe you can get the compiler's message collector from MockProject or CompilerConfiguration inside ComponentRegistrar.registerProjectComponents. Usually all ComponentRegistrars should use the same MessageCollector that is given to K2JVMCompiler by the user, right? So there must be some way for a ComponentRegistrar to access the configured MessageCollector. I don't think they can receive it through the constructor because ComponentRegistrars are often instantiated by a service locator. You can also look at the source code of KSP to see where they get it from.

• Somehow access the KotlinCompilation.messageOutputStream in a hacky way and replace it with something like TeeOutputStream.

• Just add a parameter where the user can set the OutputStream to be used for KSP. This has the disadvantage that the messages still won't be recorded in the Result class.

[yigit]

Btw, this might be just related to google/ksp#122.
KSP right now does not report errors to the compilation pipeline so once it is fixed, this issue "might" go away.

[tschuchortdev]

@yigit Originally it was simply the case that the KSP-related code had no access to the Outputstream where all the compiler messages are saved. Now that the KSP implementation has changed, deeper changes in KCT will be required to adapt and this issue should get fixed as well.