Akka: Extensions broken from Java when compiled using JDK11

[chbatey]

JDK11 is still in early release but just tried this.

With Scala 2.11.6 and JDK8/9/10 compiling an extension e.g.

object TestKitExtension extends ExtensionId[TestKitSettings] {
  override def get(system: ActorSystem): TestKitSettings = super.get(system)
  def createExtension(system: ExtendedActorSystem): TestKitSettings = new TestKitSettings(system.settings.config)
}

Where ExtentionId is:

trait ExtensionId[T <: Extension] {
  def apply(system: ActorSystem): T = {
    java.util.Objects.requireNonNull(system, "system must not be null!").registerExtension(this)
  }
  def get(system: ActorSystem): T = apply(system)
  def createExtension(system: ExtendedActorSystem): T
}

The override def get would result in a single get method in the compiled class:

javap TestKitExtension                                                                                                                                     [NORMAL] 
Warning: Binary file TestKitExtension contains akka.testkit.TestKitExtension
Compiled from "TestKitExtension.scala"
public final class akka.testkit.TestKitExtension {
  public static boolean equals(java.lang.Object);
  public static int hashCode();
  public static akka.actor.Extension apply(akka.actor.ActorSystem);
  public static akka.testkit.TestKitSettings createExtension(akka.actor.ExtendedActorSystem);
  public static akka.testkit.TestKitSettings get(akka.actor.ActorSystem);
}

When compiled with Scala 2.12.6 and JDK11:

javap TestKitExtension
Warning: Binary file TestKitExtension contains akka.testkit.TestKitExtension
Compiled from "TestKitExtension.scala"
public final class akka.testkit.TestKitExtension {
  public static boolean equals(java.lang.Object);
  public static int hashCode();
  public static akka.actor.Extension apply(akka.actor.ActorSystem);
  public static akka.testkit.TestKitSettings createExtension(akka.actor.ExtendedActorSystem);
  public static akka.testkit.TestKitSettings get(akka.actor.ActorSystem);
  public static akka.actor.Extension get(akka.actor.ActorSystem);
}

We end up with two get methods so any call to them won't compile as it is ambiguous.

[ktoso]

May want to open a ticket on scala/scala I guess

[johanandren]

Fixed now when we are up on Scala 2.12.7