CE 3131 example (maybe)

3131Example.scala

import cats.effect.std.Dispatcher
import scala.concurrent.duration._
import scala.concurrent.{Await, ExecutionContext, Future}
import cats.effect.unsafe.implicits.global

object StackTraceExample {

  case class SomeError(message: String) extends Exception
  val (dispatcher, dispatcherShutdown) = Dispatcher.parallel[IO].allocated.unsafeRunSync()

  def main(args: Array[String]): Unit = {
    val m: Future[Unit] =
      dispatcher
        .unsafeToFuture(IO.raiseError(SomeError("nice")))
        .recover {
          case SomeError(message) =>
            println(s"recovered from exception: $message")
            ()
        }(ExecutionContext.global)

    Await.result(m, 10.seconds)
  }
}

object NoTraceExample {

  case class SomeError(message: String) extends Exception
  val (dispatcher, dispatcherShutdown) = Dispatcher.sequential[IO].allocated.unsafeRunSync()

  def main(args: Array[String]): Unit = {
    val m: Future[Unit] =
      dispatcher
        .unsafeToFuture(IO.raiseError(SomeError("nice")))
        .recover {
          case SomeError(message) =>
            println(s"recovered from exception: $message")
            ()
        }(ExecutionContext.global)

    Await.result(m, 10.seconds)
  }
}

output.md

The stack trace example prints the recovery message AND the original exception

sbt:cats-effect> exampleJVM/runMain cats.effect.example.StackTraceExample
[info] running cats.effect.example.StackTraceExample
recovered from exception: nice
cats.effect.example.BrokenExample$SomeError
[success] Total time: 0 s, completed Mar. 6, 2023, 9:40:57 p.m.

The no trace example prints only the recovery message

sbt:cats-effect> exampleJVM/runMain cats.effect.example.NoTraceExample
[info] running cats.effect.example.NoTraceExample
recovered from exception: nice
[success] Total time: 2 s, completed Mar. 6, 2023, 9:40:52 p.m.