Java 9 "object scala in compiler mirror not found"

[NersesAM]

Hi,

I am trying to upgrade my project to Java 9 but scala-maven-plugin fails. Same project runs fine on Java 8.

[DEBUG] plugin jar to add :/Users/Nerses/.m2/repository/net/alchim31/maven/scala-maven-plugin/3.3.1/scala-maven-plugin-3.3.1.jar
[DEBUG] cmd:  /Library/Java/JavaVirtualMachines/jdk-9.0.4.jdk/Contents/Home/bin/java -Xbootclasspath/a:/Users/Nerses/.m2/repository/org/scala-lang/scala-library/2.12.4/scala-library-2.12.4.jar:/Users/Nerses/.m2/repository/org/scala-lang/scala-compiler/2.12.4/scala-compiler-2.12.4.jar:/Users/Nerses/.m2/repository/org/scala-lang/modules/scala-xml_2.12/1.0.6/scala-xml_2.12-1.0.6.jar:/Users/Nerses/.m2/repository/org/scala-lang/scala-library/2.12.0/scala-library-2.12.0.jar:/Users/Nerses/.m2/repository/org/scala-lang/scala-reflect/2.12.4/scala-reflect-2.12.4.jar -classpath /Users/Nerses/.m2/repository/net/alchim31/maven/scala-maven-plugin/3.3.1/scala-maven-plugin-3.3.1.jar scala_maven_executions.MainWithArgsInFile scala.tools.nsc.Main /private/var/folders/tf/grzpgmz11r32d9dtvclkr1zx9sz3ys/T/scala-maven-15243357590113591240.args
[ERROR] error: error while loading Object, Missing dependency 'object scala in compiler mirror', required by /modules/java.base/java/lang/Object.class
[ERROR] error: scala.reflect.internal.MissingRequirementError: object scala in compiler mirror not found.
[ERROR]         at scala.reflect.internal.MissingRequirementError$.signal(MissingRequirementError.scala:17)
[ERROR]         at scala.reflect.internal.MissingRequirementError$.notFound(MissingRequirementError.scala:18)
[ERROR]         at scala.reflect.internal.Mirrors$RootsBase.$anonfun$getModuleOrClass$4(Mirrors.scala:54)
[ERROR]         at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:54)
[ERROR]         at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:66)
[ERROR]         at scala.reflect.internal.Mirrors$RootsBase.getPackage(Mirrors.scala:172)
[ERROR]         at scala.reflect.internal.Definitions$DefinitionsClass.ScalaPackage$lzycompute(Definitions.scala:169)
[ERROR]         at scala.reflect.internal.Definitions$DefinitionsClass.ScalaPackage(Definitions.scala:169)
[ERROR]         at scala.reflect.internal.Definitions$DefinitionsClass.ScalaPackageClass$lzycompute(Definitions.scala:170)
[ERROR]         at scala.reflect.internal.Definitions$DefinitionsClass.ScalaPackageClass(Definitions.scala:170)
[ERROR]         at scala.reflect.internal.Definitions$DefinitionsClass.init(Definitions.scala:1423)
[ERROR]         at scala.tools.nsc.Global$Run.<init>(Global.scala:1164)
[ERROR]         at scala.tools.nsc.Driver.doCompile(Driver.scala:34)
[ERROR]         at scala.tools.nsc.MainClass.doCompile(Main.scala:24)
[ERROR]         at scala.tools.nsc.Driver.process(Driver.scala:55)
[ERROR]         at scala.tools.nsc.Driver.main(Driver.scala:68)
[ERROR]         at scala.tools.nsc.Main.main(Main.scala)
[ERROR]         at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[ERROR]         at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[ERROR]         at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[ERROR]         at java.base/java.lang.reflect.Method.invoke(Method.java:564)
[ERROR]         at scala_maven_executions.MainHelper.runMain(MainHelper.java:164)
[ERROR]         at scala_maven_executions.MainWithArgsInFile.main(MainWithArgsInFile.java:26)

Do you know what is going wrong here?
There was a similar issue in sbt and it was fixed in 0.13.17 scala/scala-xml#173

[SethTisue]

I think @retronym might be able to point you in the right direction

[retronym]

Please try upgrading to the latest minor version of Scala in the series you are using.

http://docs.scala-lang.org/overviews/jdk-compatibility/overview.html

These versions of Scala have code to read class files for the Java Standard Library from the new jrt:// virtual filesystem. Older JDKs just expose them in $JAVA_HOME/lib/rt.jar.

[NersesAM]

I'm using 2.12.4

I've tried also setting <scalaVersion>${scala-library.version}</scalaVersion> configuration, but still getting same error

[retronym]

I've just tried a minimal project and was able to compile and run on Java 9.

⚡ (java_use 9; java -version; mvn -q clean install; cd m2; mvn -q exec:java  -Dexec.mainClass="m2.M2")
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)
Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option MaxPermSize; support was removed in 8.0
/code/scala-maven-java9/m2
Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option MaxPermSize; support was removed in 8.0
hello, Maven, Scala, Java 9
/code/scala-maven-java9
⚡

Could you try that project on your machine?

[davidB]

From the initial log, I saw 2 version of scala-library 2.12.4 & 2.12.0 in bootclasspath.
Can you share the pom.xml ?

The injection of the second scala-library could be caused by a "compilerPlugins".

[NersesAM]

@retronym i tried your project and it works. Trying to see if i can reproduce, by adding more stuff to it from my project. Will report back if i can

@davidB I noticed that as well, no idea where 2.12.0 comes from. I don't think that's the problem though. When I take that cmd line from debug and run in the terminal after removing 2.12.0 form bootclasspath it still fails

[NersesAM]

@retronym @davidB I was able to reproduce it. https://github.com/NersesAM/scala-maven-java9

The problem seems to be because in that particular module I had code in Java, but tests were written in Scala. In that case /private/var/folders/tf/grzpgmz11r32d9dtvclkr1zx9sz3ys/T/scala-maven-15243357590113591240.args file doesn't contain scala-library in the classpath and build fails.

[adridadou]

that's exactly my use case. Hopefully this will be solved soon so I can still test my java code with some awesome scala !

[NersesAM]

@adridadou you can fix it by removing scala-compile-first execution and letting maven-compile-plugin to compile java files.
https://github.com/NersesAM/scala-maven-java9/blob/3a55caffa333b5c7de56e4376e4a24888f0a4add/pom.xml#L29-L36

[adridadou]

it worked! thank you very much!

[jrgleason]

Sorry to throw in a comment on such an old issue. I had a similar issue upgrading to Scala 2.13. However, when I remove the execution the Java code can no longer see the Scala code.

[slandelle]

@jrgleason Please open a new issue where you make sure to provide a sample project to reproduces your issue. Prior to that, please make that's not simply a matter of a broken maven download and the scala-library jar in your local maven cache is corrupted.

[jrgleason]

Ok will do thank you