Why is Scalatest failing now related to Java-Modules?

Question

Give this class

final case class Score(val value: BigInt, val random: Long = randomLong)
  extends Comparable[Score] {

  override def compareTo(that: Score): Int = {
    if (this.value < that.value) -1
    else if (this.value > that.value) 1
    else if (this.random < that.random) -1
    else if (this.random > that.random) 1
    else 0
  }

  override def equals(obj: _root_.scala.Any): Boolean = {
    val that = obj.asInstanceOf[Score] // (package.scala:48)
    this.value == that.value && this.random == that.random
  }
}

Everything compiles correctly. When I used to run my unit tests it worked fine a few days ago. I have not changed this code for weeks, and all my tests worked fine, in particular the tests that exercised this code. But now when I run my unit tests I get

class java.lang.Integer cannot be cast to class net.kolotyluk.leaderboard.scorekeeping.package$Score (java.lang.Integer is in module java.base of loader 'bootstrap'; net.kolotyluk.leaderboard.scorekeeping.package$Score is in unnamed module of loader 'app')
java.lang.ClassCastException: class java.lang.Integer cannot be cast to class net.kolotyluk.leaderboard.scorekeeping.package$Score (java.lang.Integer is in module java.base of loader 'bootstrap'; net.kolotyluk.leaderboard.scorekeeping.package$Score is in unnamed module of loader 'app')
    at net.kolotyluk.leaderboard.scorekeeping.package$Score.equals(package.scala:48)

Obviously something has changed, but I am not sure what.

The problem seems to be related to the Java 9 modules feature: How many unnamed modules are created in Java 9?

> java -version
java version "11.0.1" 2018-10-16 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.1+13-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.1+13-LTS, mixed mode)

My JDK has not changed. Possibly some of the versions of my maven dependencies have changed. While the code for my Score class has not changed, I have been moving things around in the package hierarchy.

Does anyone have any ideas on what else the problem may be, or other things I should investigate?

Possibly some of the versions of my maven dependencies have changed. While the code for my Score class has not changed, I have been moving things around in the package hierarchy. ... possibly that has made your module's classes to be resolved on classpath instead of modulepath with different loader(which I guess is a Classloader) — Naman
– Naman, Commented Feb 14, 2019 at 1:42

Eric Kolotyluk · Accepted Answer · 2019-02-14 05:39:01Z

1

Found the problem elsewhere. The first message was misleading, but walking further down the stack trace revealed where the problem was. It was a casting problem, but had nothing to do with modules.

answered Feb 14, 2019 at 5:39

Eric Kolotyluk

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