Exception thrown when using attempt

[yisraelU]

I am on version 2.2.0
I've been playing around with essential effects repo running the code titled ParMapNErrors

object ParMapNErrors extends IOApp {
  def run(args: List[String]): IO[ExitCode] =
    e1.attempt.debug *>
      IO("---").debug *>
      e2.attempt.debug *>
      IO("---").debug *>
      e3.attempt.debug *>
      IO.pure(ExitCode.Success)

  val ok = IO("hi").debug
  // how will debug ever evaluate
  val ko1 = IO.raiseError[String](new RuntimeException("oh!")).debug
  val ko2 = IO.raiseError[String](new RuntimeException("noes!")).debug

  val e1 = (ok, ko1).parTupled.void
  val e2 = (ko1, ok).parMapN((_, _) => ())
  val e3 = (ko1, ko2).parMapN((_, _) => ())

}

running this code both from Intellij and Sbt with (ThisBuild / fork := true) multiple times resulted in some occurrences generating the following stack trace

[info] running (fork) com.innerproduct.ee.parallel.ParMapNErrors 
[info] in debug mode: [ioapp-compute-1] hi
[info] in debug mode: [ioapp-compute-2] Left(java.lang.RuntimeException: oh!)
[info] in debug mode: [ioapp-compute-2] ---
[info] in debug mode: [ioapp-compute-2] hi
[info] in debug mode: [ioapp-compute-3] Left(java.lang.RuntimeException: oh!)
[info] in debug mode: [ioapp-compute-3] ---
[info] in debug mode: [ioapp-compute-1] Left(java.lang.RuntimeException: oh!)
[error] java.lang.RuntimeException: noes!
[error]         at com.innerproduct.ee.parallel.ParMapNErrors$.<clinit>(ParMapNErrors.scala:19)
[error]         at com.innerproduct.ee.parallel.ParMapNErrors.main(ParMapNErrors.scala)
[error]         at map @ com.innerproduct.ee.debug$DebugHelper.debug(debug.scala:15)
[error]         at map @ com.innerproduct.ee.debug$DebugHelper.debug(debug.scala:15)
[error]         at main$ @ com.innerproduct.ee.parallel.ParMapNErrors$.main(ParMapNErrors.scala:7)

For reference the "in debug mode..." is from a helper class

object debug {
  /** Extension methods for an effect of type `F[A]`. */
  implicit class DebugHelper[A](ioa: IO[A]) {

    /** Print to the console the value of the effect
     * along with the thread it was computed on. */
    def debug: IO[A] =
      for {
        a <- ioa
        tn = Thread.currentThread.getName
        _ = println(s"in debug mode: [${Colorize.reversed(tn)}] $a") // <1>
      } yield a
  }
}

[vasilmkd]

Do you mind trying with the latest Cats Effect 2 version 2.5.2?

[yisraelU]

will do

[yisraelU]

@vasilmkd I received the same results

[vasilmkd]

Thanks for the reproduction.

[arosien]

I think runtime is printing the stacktrace of the loser of the race between ko1 and ko2, and this has nothing to do with the use of attempt.

[djspiewak]

I'm almost positive that this is printing the error; the error is not being thrown past the attempt. This is expected behavior in the event that the loser of a race raises an error despite cancelation.