AsyncTests.console

[2022-03-03 16:37:09,171] INFO  [io-compute-1] c.s.r.AsyncTests:24 - internalLegacyAPI begin
[2022-03-03 16:37:09,368] INFO  [io-compute-2] c.s.r.AsyncTests:45 - cancelEff: finished
[2022-03-03 16:37:09,379] INFO  [io-compute-2] c.s.r.AsyncTests:51 - nestedAsync: onAsyncCancel
[2022-03-03 16:37:09,380] INFO  [io-compute-2] c.s.r.AsyncTests:32 - AutoCloseable.close()
[2022-03-03 16:37:09,796] INFO  [scala-execution-context-global-25] c.s.r.AsyncTests:27 - internalLegacyAPI end
[2022-03-03 16:37:11,382] INFO  [io-compute-4] c.s.r.AsyncTests:59 - ******************************
[2022-03-03 16:37:11,386] INFO  [io-compute-6] c.s.r.AsyncTests:15 - legacyAPI begin
[2022-03-03 16:37:11,387] INFO  [io-compute-6] c.s.r.AsyncTests:24 - internalLegacyAPI begin
[2022-03-03 16:37:11,584] INFO  [io-compute-7] c.s.r.AsyncTests:45 - cancelEff: finished
[2022-03-03 16:37:11,887] INFO  [scala-execution-context-global-25] c.s.r.AsyncTests:18 - legacyAPI end
[2022-03-03 16:37:11,988] INFO  [scala-execution-context-global-26] c.s.r.AsyncTests:27 - internalLegacyAPI end
[2022-03-03 16:37:11,991] INFO  [io-compute-3] c.s.r.AsyncTests:55 - nestedAsync: completed: 6
[2022-03-03 16:37:11,996] INFO  [io-compute-3] c.s.r.AsyncTests:41 - eff1: onAsyncCancel

AsyncTests.scala

import cats.effect.{IO, IOApp}
import com.typesafe.scalalogging.Logger

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future
import scala.concurrent.duration._

object AsyncTests extends IOApp.Simple {
  private val log = Logger[this.type]


  def legacyAPI(onDone: Either[Throwable, Int] => Unit): Unit = {
    log.info("legacyAPI begin")
    Future {
      Thread.sleep(500)
      log.info("legacyAPI end")
      onDone(Right(5))
    }
  }

  def internalLegacyAPI(onDone: Either[Throwable, Int] => Unit): AutoCloseable = {
    log.info("internalLegacyAPI begin")
    Future {
      Thread.sleep(600)
      log.info("internalLegacyAPI end")
      onDone(Right(6))
    }
    new AutoCloseable {
      def close(): Unit = {
        log.info("AutoCloseable.close()")
      }
    }
  }

  val eff1 = IO.async[Int] { cb =>
    IO(legacyAPI(cb)) >>
      nestedAsync >>
      IO(Some(IO {
        log.info("eff1: onAsyncCancel")
      }))
  }.flatMap(x => IO(log.info(s"eff1: completed: $x")))

  val cancelEff = IO.sleep(200.millis) >> IO(log.info("cancelEff: finished"))

  val nestedAsync = IO.async[Int] { cb =>
    IO {
      val handle = internalLegacyAPI(cb)
      Some(IO {
        log.info("nestedAsync: onAsyncCancel")
        handle.close()
      })
    }
  }.flatMap(x => IO(log.info(s"nestedAsync: completed: $x")))

  def run: IO[Unit] = {
    IO.race(nestedAsync, cancelEff).void >> IO.sleep(2000.millis) >>
      IO(log.info("******************************")) >>
      IO.race(eff1, cancelEff).void >> IO.sleep(2000.millis)
  }
}