Configure KAPT gradle plugin when an annotation processor is selected

[leonard84]

The initializr should generate the appropriate entries for KAPT if the language is Kotlin and the ConfigurationProcessor is selected as dependency.

In gradle you just need to add the processor as an dependency to the kapt configuration:
dependencies { kapt "org.springframework.boot:spring-boot-configuration-processor" }
https://stackoverflow.com/questions/37858833/spring-configuration-metadata-json-file-is-not-generated-in-intellij-idea-for-ko

Maven is a bit more verbose https://kotlinlang.org/docs/reference/kapt.html and requires declaration of the kapt goal. However, there is an open issue that prevents kapt from working if a compiler plugin (e.g. kotlin-maven-allopen) is added as dependency https://youtrack.jetbrains.com/issue/KT-18022

[snicoll]

@leonard84 start.spring.io doesn't know that entry is an annotation processor and I am not keen to bring that complexity at this point. I'd like to find another way to make it interoperable. Perhaps @sdeleuze knows?

[leonard84]

@snicoll I just tested it, you actually don't need to define the spring-boot-configuration-processor inside the maven goal again. Just executing kapt is enough for it to be picked up, if it is already on the classpath. So the question is, whether to just always include the kapt goal, which would mimic normal javac behavior of executing the annotation processors, or add logic to only add the goal if an annotation processor is present.

I haven't found a simple way for gradle to omit the kapt configuration and have it run anyways. You can use configurations.kapt.extendsFrom(configurations.compileOnly) however I don't think that this is better than just declaring the kapt dependency.

[snicoll]

I don't think that's the question. Annotation processors are automatically invoked with Java (it's part of the spec) so I'd rather have that with Koltin if we can. Implementing what you're asking means that initializr has to be aware that the dependency is in fact an annotation processor and I am not sure I like that idea.

[leonard84]

@snicoll if you want it to behave similar to Java then you just need to declare the kapt execution for maven and extend the kapt configuration for gradle configurations.kapt.extendsFrom(configurations.compileOnly).

You already put annotation processors into a special scope compileOnly, that goes for spring-boot-configuration-processor as well as lombok. As far as I can see those are the only two depdendencies that are in that scope. So in a way you already know which dependency is an annotation processor.

[snicoll]

I disagree that compileOnly means annotation processor actually. So no, I don't know those dependencies are annotation processors which brings me back to my first comment.

[sdeleuze]

Kotlin requires an explicit plugin declaration for annotation processors support and it is unlikely to change, so I don't see a better solution than adding an optional boolean metadata like requireAnnotationProcessors on dependencies that requires it + add a language specifics support to add the relevant Maven/Gradle configuration.

[snicoll]

@sdeleuze you are describing the current situation and I think it can be improved (especially when one claims 100% interoperability with Java). I've created https://youtrack.jetbrains.com/issue/KT-18289

[snicoll]

My request has been declined so we'll need to make this work here.

[dima767]

Was anyone able to successfully use kapt to generate spring boot configuration metadata? I've created the simplest possible project with Gradle, but when I run build nothing happens. https://github.com/dima767/bootiful-kt-with-config-metadata-processing If someone could point me to a right direction that would be appreciated!