Plugin: reflection inside plugins fails with class loading errors

[jpnovais]

Steps to Reproduce

1. Build a plugin that uses Jackson with Kotlin module registered
2. Try to serialize a Kotlin class to JSON

Example of such failing plugin can be found here

Expected behavior:
To correctly serialize the class to JSON

Actual behavior:
Fails with class loading error

class kotlin.jvm.internal.ClassReference cannot be cast to class kotlin.reflect.jvm.internal.KClassImpl (kotlin.jvm.internal.ClassReference is in unnamed module of loader 'app'; kotlin.reflect.jvm.internal.KClassImpl is in unnamed module of loader java.net.URLClassLoader @7cfac39f)

Frequency:
Always

Versions (Add all that apply)

• Software version: docker image hyperledger/besu:25.1.0

Additional Information

As a workaround, if we override Besu CLASSPATH to include the plugin's folder, all classes are loaded inside the main classloader and the problem goes away.

CLASSPATH=/opt/besu/lib/*:/opt/besu/plugins/*