mimaReportBinaryIssues on a POM-only module results in java.lang.RuntimeException: not a directory or jar file

[DavidGregory084]

Spotted in typelevel/typelevel-scalafix#18:

[error] java.lang.RuntimeException: not a directory or jar file: /home/runner/work/typelevel-scalafix/typelevel-scalafix/target/rules-aggregate/target/scala-2.13/classes
[error] 	at scala.sys.package$.error(package.scala:30)
[error] 	at com.typesafe.tools.mima.lib.MiMaLib.$anonfun$createPackage$1(MiMaLib.scala:13)
[error] 	at scala.Option.getOrElse(Option.scala:189)
[error] 	at com.typesafe.tools.mima.lib.MiMaLib.createPackage(MiMaLib.scala:13)
[error] 	at com.typesafe.tools.mima.lib.MiMaLib.collectProblems(MiMaLib.scala:34)
[error] 	at com.typesafe.tools.mima.plugin.SbtMima$.checkBC$1(SbtMima.scala:24)
[error] 	at com.typesafe.tools.mima.plugin.SbtMima$.runMima(SbtMima.scala:27)
[error] 	at com.typesafe.tools.mima.plugin.MimaPlugin$.$anonfun$binaryIssuesFinder$5(MimaPlugin.scala:99)
[error] 	at scala.collection.Iterator$$anon$10.next(Iterator.scala:461)
[error] 	at scala.collection.Iterator.foreach(Iterator.scala:943)
[error] 	at scala.collection.Iterator.foreach$(Iterator.scala:943)
[error] 	at scala.collection.AbstractIterator.foreach(Iterator.scala:1431)
[error] 	at com.typesafe.tools.mima.plugin.MimaPlugin$.$anonfun$projectSettings$1(MimaPlugin.scala:26)
[error] 	at com.typesafe.tools.mima.plugin.MimaPlugin$.$anonfun$projectSettings$1$adapted(MimaPlugin.scala:25)
[error] 	at scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] 	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] 	at sbt.std.Transform$$anon$4.work(Transform.scala:68)
[error] 	at sbt.Execute.$anonfun$submit$2(Execute.scala:282)
[error] 	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:23)
[error] 	at sbt.Execute.work(Execute.scala:291)
[error] 	at sbt.Execute.$anonfun$submit$1(Execute.scala:282)
[error] 	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] 	at sbt.CompletionService$$anon$2.call(CompletionService.scala:64)
[error] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] 	at java.util.concurrent.Executors$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:750)
[error] (typelevel-scalafix-rules / mimaReportBinaryIssues) not a directory or jar file: /home/runner/work/typelevel-scalafix/typelevel-scalafix/target/rules-aggregate/target/scala-2.13/classes

I think the problem is that we are trying to execute mimaReportBinaryIssues on an empty module. That module only exists to publish a pom file that depends on other modules in the project.

The module is defined like so:

lazy val `typelevel-scalafix-rules` = project
  .in(file("target/rules-aggregate"))
  .dependsOn(catsRules, catsEffectRules)
  .settings(
    moduleName := "typelevel-scalafix",
    tlVersionIntroduced ++= List("2.12", "2.13").map(_ -> "0.1.2").toMap
  )

I'm not exactly sure if this is the correct way to declare a module for this purpose but I guess MiMa should probably fail slightly more gracefully.

[armanbilge]

IMHO it seems reasonable if there are no class files available to proceed normally. After all, if MiMa compares them to previous artifacts and finds there are classes in them, then it will raise the usual errors.