NoSuchMethodError when using Scala in R with rscala - r

Question

I'm having trouble using rscala package in R to call precompiled Scala code.
I have an Scala project running on version 2.11.12. I build a fat jar with sbt-assembly and make it available to rscala through rscala::scala("path-to-jar.jar")
But whenever I try to run any function/method/whatever from the package, I get the following error:
java.lang.reflect.InvocationTargetException
java.lang.NoSuchMethodError: scala.Predef$.refArrayOps([Ljava/lang/Object;)Lscala/collection/mutable/ArrayOps;
at myPackage.myClass$.myMethod(myClass.scala:116)
at $line6.$read$$iw$$iw$$iw$$iw$.$anonfun$res0$1(<console>:16)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.ddahl.rscala.server.Server.$anonfun$invoke$3(Server.scala:305)
at org.ddahl.rscala.server.Server.wrap(Server.scala:47)
at org.ddahl.rscala.server.Server.invoke(Server.scala:305)
at org.ddahl.rscala.server.Server.run(Server.scala:400)
at org.ddahl.rscala.server.Main$.delayedEndpoint$org$ddahl$rscala$server$Main$1(Main.scala:105)
at org.ddahl.rscala.server.Main$delayedInit$body.apply(Main.scala:11)
at scala.Function0.apply$mcV$sp(Function0.scala:39)
at scala.Function0.apply$mcV$sp$(Function0.scala:39)
at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
at scala.App.$anonfun$main$1$adapted(App.scala:80)
at scala.collection.immutable.List.foreach(List.scala:392)
at scala.App.main(App.scala:80)
at scala.App.main$(App.scala:78)
at org.ddahl.rscala.server.Main$.main(Main.scala:11)
at org.ddahl.rscala.server.Main.main(Main.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at scala.reflect.internal.util.ScalaClassLoader.$anonfun$run$2(ScalaClassLoader.scala:106)
at scala.reflect.internal.util.ScalaClassLoader.asContext(ScalaClassLoader.scala:41)
at scala.reflect.internal.util.ScalaClassLoader.asContext$(ScalaClassLoader.scala:37)
at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.asContext(ScalaClassLoader.scala:132)
at scala.reflect.internal.util.ScalaClassLoader.run(ScalaClassLoader.scala:106)
at scala.reflect.internal.util.ScalaClassLoader.run$(ScalaClassLoader.scala:98)
at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:132)
at scala.tools.nsc.CommonRunner.run(ObjectRunner.scala:28)
at scala.tools.nsc.CommonRunner.run$(ObjectRunner.scala:27)
at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:45)
at scala.tools.nsc.CommonRunner.runAndCatch(ObjectRunner.scala:35)
at scala.tools.nsc.CommonRunner.runAndCatch$(ObjectRunner.scala:34)
at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:45)
at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:73)
at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:92)
at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:103)
at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:108)
at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
Error in pop(details, transcompileInfo, envir) : Invocation error.
It does allow me to import its classes and objects, so it does seem to be in the classpath, but that's it.
My build.sbt includes crossScalaVersions := Seq("2.11.12", "2.12.7", "2.13.0-M5") as required in the package.
Any thoughts? It seems like a scala version error, since running rscala::scalaConfig() shows me it is using scalaFullVersion 2.12.8, but I can't seem to choose a scala installation, so I can't really expect this to be the problem.
EDIT:
After Jasper-M's suggestion, I set environment variable RSCALA_SCALA_MAJORVERSION=2.11 and reexecuted the config with rscala::scalaConfig(download='scala'). Now it returns scalaMajorVersion as 2.11.
Now, when I create an instance of the scala bridge with rscala::scala(), it returns a message (not an error) saying:
cat: /release: No such file or directory
If I run println() it compiles with no issues. However, if I instantiate the scala bridge with a precompiled fat JAR of my own and do ANYTHING (like println), it returns the following error:
error: error while loading package, class file '$HOME/.rscala/scala/lib/scala-library.jar(scala/reflect/package.class)' is broken
(class java.lang.RuntimeException/Scala class file does not contain Scala annotation)
error: error while loading package, class file '$HOME/.rscala/scala/lib/scala-library.jar(scala/package.class)' is broken
(class java.lang.RuntimeException/Scala class file does not contain Scala annotation)
error: error while loading package, class file '$HOME/.rscala/scala/lib/scala-library.jar(scala/reflect/package.class)' is broken
(class java.lang.RuntimeException/Scala class file does not contain Scala annotation)
error: error while loading package, class file '$HOME/.rscala/scala/lib/scala-library.jar(scala/package.class)' is broken
(class java.lang.RuntimeException/Scala class file does not contain Scala annotation)
error: error while loading Predef, class file '$HOME/.rscala/scala/lib/scala-library.jar(scala/Predef.class)' is broken
(class java.lang.RuntimeException/Scala class file does not contain Scala annotation)
I'm really clueless here. Any ideas?

Answer 1

It's most definitely a Scala version error.
My best guess is that you have to set the environment variable RSCALA_SCALA_MAJORVERSION=2.11 . E.g. by calling
Sys.setenv(RSCALA_SCALA_MAJORVERSION = "2.11")
and then run
rscala::scalaConfig(download = "scala")