Supporting Maven and Kotlin

[sdelamo]

Maven KAPT and Java

For Java, we can add exclusions with the Maven Plugin for annotation processors:

<annotationProcessorPaths combine.children="append">
...
    <path>
        <groupId>io.micronaut.serde</groupId>
        <artifactId>micronaut-serde-processor</artifactId>
      <version>${micronaut.serialization.version}</version>
      <exclusions>
           <exclusion>
               <groupId>io.micronaut</groupId>
               <artifactId>micronaut-inject</artifactId>
          </exclusion>
      </exclusions>
   </path>
</annotationProcessorPaths>

Maven KAPT and Kotlin

However, the KAPT Maven Plugin does not support exclusions:

  <annotationProcessorPaths combine.self="override">
     <annotationProcessorPath>
          <groupId>io.micronaut.serde</groupId>
           <artifactId>micronaut-serde-processor</artifactId>
           <version>${micronaut.serialization.version}</version>
    </annotationProcessorPath>
</annotationProcessorPaths>

Moreover, KAPT is in maintenance mode. Thus, I don't expect the kapt maven plugin to add exclusions support.

Changes in Core break Kotlin Maven Kapt support

In Micronaut Framework 4.2.0, we did changes to Micronaut Core AnnotationValue. If platform contains a module, which contributes an annotation processor, built with a previous version of core (E.g. core version in Micronaut Platform is 4.2.0, but Micronaut Data in platform was built with core 4.1.6), the Kotlin Maven applications break.

Caused by: Java.lang.NoSuchMethodError: Micronaut constructor io.micronaut.core.annotation.AnnotationValue(String,Map,AnnotationDefaultValuesProvider) not found. Most likely reason for this issue is that you are running a newer version of Micronaut with code compiled against an older version. Please recompile the offending classes
	at io.micronaut.core.reflect.ReflectionUtils.newNoSuchConstructorInternalError(ReflectionUtils.java:430)

Since KSP is not supported for Maven to keep supporting Maven and Kotlin, the only workaround is to build and release every module that adds an annotation processor with the same core version as in Micronaut Platform.

I had to release again:

• Micronaut Data
• Micronaut Tracing
• Micronaut MicroStream
• Micronaut Micrometer
• Micronaut Serialization
• Micronaut OpenAPI
• Micronaut Spring
• Micronaut JAX-RS
• Micronaut Security
• Micronaut Validation

This is a horrible coupling.

Can we solve this issue?