Build fails when injecting CCUD plugin into existing DV project using develocity.buildCache

[bigdaz]

If a project applies the com.gradle.develocity plugin (but not the CCUD plugin), and that project is configured to use develocity.buildCache, applying the CCUD plugin via init-script will cause the build to fail.

For example given this settings.gradle.kts:

plugins {
    id("com.gradle.develocity").version("3.18.2")
}

develocity {
    buildScan {
        uploadInBackground = false
        termsOfUseUrl = "https://gradle.com/help/legal-terms-of-use"
        termsOfUseAgree = "yes"
    }
}

buildCache {
    remote(develocity.buildCache)
}

rootProject.name = "inject-ccud"

The build fails with this exception (scan):

* What went wrong:
Failed to apply plugin class 'com.gradle.CommonCustomUserDataGradlePlugin'.
> com.gradle.develocity.agent.gradle.internal.a.b_Decorated cannot be cast to com.gradle.develocity.agent.gradle.buildcache.DevelocityBuildCache

Applying the CCUD plugin directly to the project does not cause this failure. However, the issue to that the Develocity and CCUD plugins are loaded in different Classloaders, and the DevelocityBuildCache type is not shared.

This issue can be fixed in the CCUD plugin by marshalling calls between the 2 classloaders.

Reproducer: https://github.com/bigdaz/develocity-ci-injection-issue-19