native-image 21.1.0 fails on scala.util.Random$

[taig]

GraalVM 21.1.0 has just been released, but my builds are failing unfortunately.

Error: Detected an instance of Random/SplittableRandom class in the image heap. Instances created during image generation have cached seed values and don't behave as expected.  Object has been initialized by the scala.util.Random$ class initializer with a trace: 
 	at java.util.Random.<init>(Random.java:105)
	at scala.util.Random.<init>(Random.scala:30)
	at scala.util.Random$.<init>(Random.scala:260)
	at scala.util.Random$.<clinit>(Random.scala:260)
. Try avoiding to initialize the class that caused initialization of the object. The object was probably created by a class initializer and is reachable from a static field. You can request class initialization at image runtime by using the option --initialize-at-run-time=<class-name>. Or you can write your own initialization methods and call them explicitly from your main entry point.
Detailed message:
Trace: Object was reached by 
	reading field scala.util.Random.self of
		constant scala.util.Random$@5e16dff3 reached by 
	scanning method org.http4s.client.PoolManager.$anonfun$borrow$10(PoolManager.scala:199)
Call path from entry point to org.http4s.client.PoolManager.$anonfun$borrow$10(Iterable): 
	at org.http4s.client.PoolManager.$anonfun$borrow$10(PoolManager.scala:199)
	at org.http4s.client.PoolManager$$Lambda$2848/0x00000007c26b5c40.apply(Unknown Source)
	at scala.collection.Iterator$$anon$22.next(Iterator.scala:1008)
	at scala.collection.convert.JavaCollectionWrappers$IteratorWrapper.next(JavaCollectionWrappers.scala:29)
	at com.oracle.svm.jni.access.JNIReflectionDictionary.unsetEntryPoints(JNIReflectionDictionary.java:178)
	at com.oracle.svm.jni.functions.JNIFunctions.UnregisterNatives(JNIFunctions.java:398)
	at com.oracle.svm.core.code.IsolateEnterStub.JNIFunctions_UnregisterNatives_07af9442aa98f893dd700b47b363fa08a3f7e240(generated:0)

Steps to reproduce the behavior

1. Set GraalVM version to 21.1.0
2. Run sbt/nativeImage on code that references scala.util.Random$

Solution

scala.util.Random$ extends scala.util.Random and thereby causes a static initialization of java.util.Random which is not allowed, as the error message above suggests. I believe we should therefore add --initialize-at-run-time=scala.util.Random$ to the default options of this plugin.

[olafurpg]

Thank you for reporting! Can you confirm that --initialize-at-run-time=scala.util.Random$ fixes the problem? We can certainly enable something like that by default in this plugin.

[taig]

After adding the option to my build, the native-image generation passed without issues again and the executables are doing fine in production. As this is a Scala-related issue, this project seems to be the best place to handle it. However, I have poor understanding of the native-image mechanics and don't fully get why this change became necessary, so I figured I'll contribute this as a suggestion and get some more eyes on it.

The issue did of course also pop up in numerous Java libraries which also appear to be resolved via runtime init quarkusio/quarkus#14904.

If you agree with the approach, I would be happy to submit a PR.