FileAlreadyExistsException on several parallel builds of the same project with Scala CLI

[Gedochao]

After exiting Bloop

scala-cli bloop exit --power

and then starting several (~20 on my local machine) parallel builds of the same, simple hello world script with Bloop, I'm getting

Error: Unexpected error when copying /Users/pchabelski/IdeaProjects/scala-cli/out/integration/tmpDirBase.dest/working-dir/run-601145553/test-2/.scala-build/.bloop/test-2_d3ad16f7cb-759f1d75c0/bloop-internal-classes/main-wj4lCK8TRUmv7JMKIj2d_w==/script$package.class to /Users/pchabelski/IdeaProjects/scala-cli/out/integration/tmpDirBase.dest/working-dir/run-601145553/test-2/.scala-build/test-2_d3ad16f7cb-759f1d75c0/classes/main/script$package.class, you might need to restart the build server.
java.nio.file.FileAlreadyExistsException: /Users/pchabelski/IdeaProjects/scala-cli/out/integration/tmpDirBase.dest/working-dir/run-601145553/test-2/.scala-build/test-2_d3ad16f7cb-759f1d75c0/classes/main/script$package.class
        at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:94)
        at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106)
        at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111)
        at java.base/sun.nio.fs.UnixCopyFile.copyFile(UnixCopyFile.java:246)
        at java.base/sun.nio.fs.UnixCopyFile.copy(UnixCopyFile.java:603)
        at java.base/sun.nio.fs.UnixFileSystemProvider.copy(UnixFileSystemProvider.java:258)
        at java.base/java.nio.file.Files.copy(Files.java:1305)
        at bloop.io.ParallelOps$.copy$1(ParallelOps.scala:169)
        at bloop.io.ParallelOps$.$anonfun$copyDirectories$8(ParallelOps.scala:194)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
        at monix.eval.internal.TaskRunLoop$.startFuture(TaskRunLoop.scala:494)
        at monix.eval.Task.runToFutureOpt(Task.scala:586)
        at monix.eval.internal.TaskDeprecated$Extensions.runSyncMaybeOptPrv(TaskDeprecated.scala:128)
        at monix.eval.internal.TaskDeprecated$Extensions.$anonfun$coeval$1(TaskDeprecated.scala:303)
        at monix.eval.Coeval$Always.apply(Coeval.scala:1451)
        at monix.eval.Coeval.value(Coeval.scala:258)
        at bloop.io.ParallelOps$.$anonfun$copyDirectories$7(ParallelOps.scala:234)
        at monix.reactive.internal.consumers.ForeachAsyncConsumer$$anon$1.onNext(ForeachAsyncConsumer.scala:44)
        at monix.reactive.internal.consumers.LoadBalanceConsumer$$anon$1.$anonfun$signalNext$1(LoadBalanceConsumer.scala:218)
        at monix.execution.internal.InterceptRunnable.run(InterceptRunnable.scala:27)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
        at java.base/java.lang.Thread.run(Thread.java:833)

This seems to fail on

bloop/backend/src/main/scala/bloop/io/ParallelOps.scala

Line 169 in e52ee2e

StandardCopyOption.REPLACE_EXISTING

Perhaps a lock on the file (per client) would make sense?

Relevant to:

• Improve handling for parallel Scala CLI runs VirtusLab/scala-cli#3399
• ArrayIndexOutOfBoundsException when running more than one process in parallel VirtusLab/scala-cli#2034
• Bloop rifle fails on ??? unimplemented cases when several processes try to create Bloop at once #2550

cc @tgodzik

[tgodzik]

This should be fixed, there are some other problems, but they are more related to how Scala CLI modifies classfiles