IMain interpret does not reset context classloader

[scabug]

Calling interpret sets the current thread's context classloader, but fails to reset it to its previous state when returning from that method.

The following workaround illustrates the problem:

    val th = Thread.currentThread()
    val cl = th.getContextClassLoader
    try {
      imain.interpret(text)
    } finally {
      th.setContextClassLoader(cl)
    }

Jason Zaugg suggests that the following might be the regression: scala/scala@3a30af1#diff-36a995091016ecd5cdb97e267764e05aL538

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8521?orig=1
Reporter: @Sciss
Affected Versions: 2.11.0

[scabug]

@gourlaysama said:
I can't seem to be able to reproduce it...

$ cat test.scala
import scala.tools.nsc.interpreter.IMain

object Test extends App {
  val cl = Thread.currentThread().getContextClassLoader
  println(cl)

  val imain = new IMain()
  imain.interpret("println(42)")
 
  val cl2 = Thread.currentThread().getContextClassLoader
  println(cl2)

  println(cl == cl2)
}
$ scala Test
scala.reflect.internal.util.ScalaClassLoader$URLClassLoader@1f32e575
42
scala.reflect.internal.util.ScalaClassLoader$URLClassLoader@1f32e575
true

[scabug]

Martin Grotzke (martin.grotzke) said (edited on May 15, 2015 10:12:49 PM UTC):
I'm also experiencing this with iMain.compile. Before iMain.compile the thread context CL is sun.misc.Launcher$AppClassLoader@368239c8 and afterwards it is scala.reflect.internal.util.ScalaClassLoader$URLClassLoader@39094bde.

This happened in tests (scalatest), where in consequence other tests that try to create an ActorSystem fail because in akka some components are created via reflection relying on the thread context CL:

    sbt.ForkMain$ForkError: interface akka.actor.Scheduler is not assignable from class akka.actor.LightArrayRevolverScheduler
            at akka.actor.ReflectiveDynamicAccess$$anonfun$getClassFor$1.apply(DynamicAccess.scala:69)
            at akka.actor.ReflectiveDynamicAccess$$anonfun$getClassFor$1.apply(DynamicAccess.scala:66)
            at scala.util.Try$.apply(Try.scala:191)
            at akka.actor.ReflectiveDynamicAccess.getClassFor(DynamicAccess.scala:66)
            at akka.actor.ReflectiveDynamicAccess.createInstanceFor(DynamicAccess.scala:84)
            at akka.actor.ActorSystemImpl.createScheduler(ActorSystem.scala:676)
            at akka.actor.ActorSystemImpl.<init>(ActorSystem.scala:576)
            at akka.actor.ActorSystem$.apply(ActorSystem.scala:142)
            at akka.actor.ActorSystem$.apply(ActorSystem.scala:109)
            at foo.bar.SomeSpec.<init>(SomeSpec.scala:32)
            at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
            at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
            at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
            at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
            at java.lang.Class.newInstance(Class.java:442)
            at org.scalatest.tools.Framework$ScalaTestTask.execute(Framework.scala:641)
            at sbt.ForkMain$Run$2.call(ForkMain.java:294)
            at sbt.ForkMain$Run$2.call(ForkMain.java:284)
            at java.util.concurrent.FutureTask.run(FutureTask.java:266)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
            at java.lang.Thread.run(Thread.java:745)

I can reproduce this with this App run from sbt with runMain foo.Main:

package foo

import javax.script.ScriptEngineManager

object Main extends App {

  val ngine = new ScriptEngineManager().getEngineByName("scala")

  val iMain = ngine.asInstanceOf[scala.tools.nsc.interpreter.IMain]
  class Foo
  iMain.settings.embeddedDefaults[Foo]

  println(Thread.currentThread().getContextClassLoader)
  iMain.compile("val x = 1")
  println(Thread.currentThread().getContextClassLoader)

}

scala version is 2.11.6

[scabug]

@som-snytt said:
scala/scala#5657

[som-snytt]

https://users.scala-lang.org/t/java-scriptengine-cannot-cast-to-scripted/1166

recaps the reproduction from two years ago.

[som-snytt]

Another mode of suffering

https://gitter.im/scala/scala?at=59b75be4177fb9fe7eacd7f1

https://gist.github.com/cnestor/2c1658d67cf2997a5cc586c7fb0b7fb0

where log4j loads script engines. And then everything breaks.