Kotlin multiplatform library aar wont show sources when added as Dependency in Android Studio

Question

I'm trying to publish a Kotlin Multiplatform library including sources using the maven-publish plugin. This is generally working but when I want to have a look at the code of the dependency inside my Android Studio project I can't see the sources but instead will see decompiled Kotlin code.

I tried several approaches of adding a sources.jar to the generated aar file already. Right now I'm following this approach: https://stackoverflow.com/a/28704799. But I still can't see the sources(gradle clean cache and restart included).

Library build.gradle:

apply plugin: 'maven-publish'

task sourceJar(type: Jar) {
    from android.sourceSets.main.java.srcDirs
    classifier "sources"
}

publishing {
    publications {
        bar(MavenPublication) {
            groupId 'com.foo'
            artifactId 'bar'
            version '0.1'
            artifact(sourceJar)
            artifact("$buildDir/outputs/aar/bar-release.aar")
        }
    }
    repositories {
        maven {
            url "$buildDir/repo"
        }
    }
}

I also tried using different sourceSets like specifying one by name since the content of android.sourceSets.main.java.srcDirs is leading to a path where no sources are inside.

The library is included in the app project like this:

dependencies {
  implementation 'com.foo:bar:0.1'
}

Looking at the local maven repository I can even see the bar-release-sources.jar but it seems like it's not part of the aar?