java.lang.ClassNotFoundException: build_.package_$

[He-Pin]

Mill version:
Local installed 0.12.5 with project configured 0.12.0

How I fixed it:

Delete the out folder.

Exception:

hepin@Mac cask % mill clean
[68/68] ============================== clean ==============================
An unexpected error occurred java.lang.ClassNotFoundException: build_.package_$
java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)
java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:595)
java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:528)
mill.runner.MillBuildBootstrap$.getRootModule(MillBuildBootstrap.scala:429)
mill.runner.MillBuildBootstrap.evaluateRec(MillBuildBootstrap.scala:155)
mill.runner.MillBuildBootstrap.$anonfun$evaluate$1(MillBuildBootstrap.scala:56)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.runner.MillBuildBootstrap.evaluate(MillBuildBootstrap.scala:55)
mill.runner.MillMain$.$anonfun$main0$16(MillMain.scala:270)
mill.runner.TailManager.withOutErr(TailManager.scala:37)
mill.runner.MillMain$.$anonfun$main0$15(MillMain.scala:271)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.$anonfun$withStreams$9(SystemStreams.scala:104)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.$anonfun$withStreams$8(SystemStreams.scala:103)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.$anonfun$withStreams$7(SystemStreams.scala:102)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
scala.Console$.withErr(Console.scala:193)
mill.api.SystemStreams$.$anonfun$withStreams$6(SystemStreams.scala:101)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
scala.Console$.withOut(Console.scala:164)
mill.api.SystemStreams$.$anonfun$withStreams$5(SystemStreams.scala:100)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
scala.Console$.withIn(Console.scala:227)
mill.api.SystemStreams$.$anonfun$withStreams$4(SystemStreams.scala:99)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.withStreams(SystemStreams.scala:98)
mill.runner.MillMain$.$anonfun$main0$14(MillMain.scala:252)
scala.util.Using$.resource(Using.scala:296)
mill.runner.MillMain$.$anonfun$main0$10(MillMain.scala:247)
mill.runner.MillMain$.$anonfun$withOutLock$1(MillMain.scala:460)
scala.util.Using$.resource(Using.scala:296)
mill.runner.MillMain$.withOutLock(MillMain.scala:458)
mill.runner.MillMain$.$anonfun$main0$9(MillMain.scala:247)
mill.runner.MillMain$.$anonfun$main0$9$adapted(MillMain.scala:225)
mill.runner.Watching$.watchLoop(Watching.scala:29)
mill.runner.MillMain$.$anonfun$main0$8(MillMain.scala:277)
mill.runner.MillMain$.$anonfun$main0$8$adapted(MillMain.scala:213)
scala.util.Using$.resource(Using.scala:296)
mill.runner.MillMain$.$anonfun$main0$2(MillMain.scala:213)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.runner.MillMain$.$anonfun$main0$1(MillMain.scala:111)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.$anonfun$withStreams$9(SystemStreams.scala:104)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.$anonfun$withStreams$8(SystemStreams.scala:103)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.$anonfun$withStreams$7(SystemStreams.scala:102)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
scala.Console$.withErr(Console.scala:193)
mill.api.SystemStreams$.$anonfun$withStreams$6(SystemStreams.scala:101)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
scala.Console$.withOut(Console.scala:164)
mill.api.SystemStreams$.$anonfun$withStreams$5(SystemStreams.scala:100)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
scala.Console$.withIn(Console.scala:227)
mill.api.SystemStreams$.$anonfun$withStreams$4(SystemStreams.scala:99)
scala.util.DynamicVariable.withValue(DynamicVariable.scala:59)
mill.api.SystemStreams$.withStreams(SystemStreams.scala:98)
mill.runner.MillMain$.main0(MillMain.scala:110)
mill.runner.MillServerMain.main0(MillServerMain.scala:73)
mill.runner.MillServerMain.main0(MillServerMain.scala:36)
mill.main.server.Server.$anonfun$handleRun$2(Server.scala:195)
java.base/java.lang.Thread.run(Thread.java:1575)
mill-server/ exitCode file not found

[lefou]

Mill version: 0.12.5 with configured 0.12.0

What does that mean?

[He-Pin]

I installed 0.12.5, and cask is configured 0.12.0

[lihaoyi]

This feels like its the same problem we had before with failures on Mill version change

[lefou]

You mean #3874 ?

This was fixed for 0.12.2, but this issue is about using Mill 0.12.0. I think this issue is most likely invalid.