Build Bug: org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool is not on the classpath

[He-Pin]

Even the PekkoJdk9ForkJoinPool is on the final result jar, but it does not on the classpath.

How to reproduce:

1. using Java 21
2. sbt console

Welcome to Scala 2.13.16 (Java HotSpot(TM) 64-Bit Server VM, Java 21.0.5).

scala> classOf[org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool]
                                         ^
       error: type PekkoJdk9ForkJoinPool is not a member of package org.apache.pekko.dispatch

scala> 

I think that's maybe caused by of the Jdk9.scala

[pjfanning]

Existing workaround:

pekko/actor/src/main/scala/org/apache/pekko/dispatch/ForkJoinExecutorConfigurator.scala

Lines 99 to 114 in d30e29d

	private def pekkoJdk9ForkJoinPoolClassOpt: Option[Class[_]] =
	Try(Class.forName("org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool")).toOption
	private lazy val pekkoJdk9ForkJoinPoolHandleOpt: Option[MethodHandle] = {
	if (JavaVersion.majorVersion == 8) {
	None
	} else {
	pekkoJdk9ForkJoinPoolClassOpt.map { clz =>
	val methodHandleLookup = MethodHandles.lookup()
	val mt = MethodType.methodType(classOf[Unit], classOf[Int],
	classOf[ForkJoinPool.ForkJoinWorkerThreadFactory],
	classOf[Int], classOf[Thread.UncaughtExceptionHandler], classOf[Boolean])
	methodHandleLookup.findConstructor(clz, mt)
	}
	}
	}

[raboof]

The classpath of which module are you referring to?

If this is about actor-tests, perhaps you could use a similar technique as at https://github.com/apache/pekko/blob/main/build.sbt#L419 at https://github.com/apache/pekko/blob/main/build.sbt#L128

[He-Pin]

1. Start SBT shell with Java 21/23
2. type console
3. classOf[org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool, class not found.

OR:
When Run a TestJdk9 / testOnly $someJDK21Test on Java 21, and in $someJDK21Test use Class.forName("org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool") , then a ClassNotFoundException throws.

[He-Pin]

I see no integration test for org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool， which must been tested manually.
as the full classpath has no org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool classes, just the product jar, where is the integration test for it @pjfanning ? shouldn't we expect a test for that lives in the scala-jdk9-only folder?

[He-Pin]

@pjfanning It's not I don't know how to write the code, but with the current setup, it can't be integrated tested, if you add an integration test for org.apache.pekko.dispatch.PekkoJdk9ForkJoinPool and show it works, I'm very happy to follow.