Java 9 "object scala in compiler mirror not found"

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 https://github.com/scala/scala-xml/issues/173

[adridadou]

it worked! thank you very much!

[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.