Weird versioning issues with SBT after upgrade to 2.12.8

[liufengyun]

After #5595, when I run the test set of ScalaTest based on Dotty, I got a weird runtime exception:

[error] java.lang.NoSuchMethodError: scala.reflect.internal.util.package$.SomeOfNil()Lscala/Option;
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.$anonfun$newT1NoParamsMethod$1(Definitions.scala:1360)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.newPolyMethod(Definitions.scala:1346)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.newT1NoParamsMethod(Definitions.scala:1360)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.Object_isInstanceOf$lzycompute(Definitions.scala:1118)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.Object_isInstanceOf(Definitions.scala:1118)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.syntheticCoreMethods$lzycompute(Definitions.scala:1395)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.syntheticCoreMethods(Definitions.scala:1379)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.symbolsNotPresentInBytecode$lzycompute(Definitions.scala:1409)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.symbolsNotPresentInBytecode(Definitions.scala:1409)
[error] 	at scala.reflect.internal.Definitions$DefinitionsClass.init(Definitions.scala:1465)
[error] 	at scala.reflect.runtime.JavaUniverse.init(JavaUniverse.scala:154)
[error] 	at scala.reflect.runtime.JavaUniverse.<init>(JavaUniverse.scala:93)
[error] 	at scala.reflect.runtime.package$.universe$lzycompute(package.scala:29)
[error] 	at scala.reflect.runtime.package$.universe(package.scala:29)
[error] 	at org.scalatest.tools.Framework.runner(Framework.scala:1005)
[error] 	at sbt.Defaults$.$anonfun$createTestRunners$1(Defaults.scala:944)
[error] 	at scala.collection.TraversableLike.$anonfun$map$1(TraversableLike.scala:233)
[error] 	at scala.collection.immutable.Map$Map2.foreach(Map.scala:156)
[error] 	at scala.collection.TraversableLike.map(TraversableLike.scala:233)
[error] 	at scala.collection.TraversableLike.map$(TraversableLike.scala:226)
[error] 	at scala.collection.AbstractTraversable.map(Traversable.scala:104)
[error] 	at sbt.Defaults$.createTestRunners(Defaults.scala:938)
[error] 	at sbt.Defaults$.allTestGroupsTask(Defaults.scala:1000)
[error] 	at sbt.Defaults$.$anonfun$testTasks$10(Defaults.scala:756)
[error] 	at scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error] 	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:40)
[error] 	at sbt.std.Transform$$anon$4.work(System.scala:67)
[error] 	at sbt.Execute.$anonfun$submit$2(Execute.scala:269)
[error] 	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error] 	at sbt.Execute.work(Execute.scala:278)
[error] 	at sbt.Execute.$anonfun$submit$1(Execute.scala:269)
[error] 	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] 	at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] 	at java.lang.Thread.run(Thread.java:748)

The error does not make any sense. From source code, we can see SomeOfNil is defined in scala-reflect-2.12.8. I checked the binary file, the method indeed exists. On the other hand, if earlier versions of scala-reflect is used, it can not use SomeOfNil, otherwise scala-reflect will not compile.

It seems the only explanation is that there are more than one JAR of scala-reflect on java class path, some classes are loaded from scala-reflect-2.12.8, but others are from the other version.

The change in #5595 makes the situation above possible:

• The latest SBT 1.2.7 depends on scala-reflect-2.12.7.jar
• ScalaTest depends on scala-reflect, which is rewritten to ch.epfl.lamp:scala-reflect, which eventually depends on scala-reflect-2.12.8 due to Override scala organization and version transitively at the Ivy level sbt/sbt#2634 .

After the changes in #5595, all tests based on (ScalaTest, Dotty, SBT) will break. Reverting #5595 only temporarily addresses the issue, as this seems to be a deep problem with the sbt.

Note: fork in Test := true does not help.

[liufengyun]

Close now, this is more a problem of SBT.