[GitHub] [incubator-pekko-management] mdedetrich commented on pull request #74: Replace future flatMap + recoverWith combo with transform

["mdedetrich (via GitHub)" <gi...@apache.org>]

mdedetrich commented on PR #74:
URL: https://github.com/apache/incubator-pekko-management/pull/74#issuecomment-1557331560

   @lolgab So we had this discussion on discord (see https://discord.com/channels/632150470000902164/632150470000902166/1110163014398787625) but tl;dr the usage of `Function` here is misleading and it should really be a `PartialFunction` because in the failure case it doesn't actually create a match error, it in fact passes through just like a `PartialFunction` does, you can verify this in Scala repl i.e.
   
   ```
   scala> class MyException extends Exception
   class MyException
   
   scala> val f1 = Future.failed(new MyException)
   val f1: scala.concurrent.Future[Nothing] = Future(Failure(MyException))
   
   scala> val f2 = Future.failed(new RuntimeException("bleh"))
   val f2: scala.concurrent.Future[Nothing] = Future(Failure(java.lang.RuntimeException: bleh))
   
   scala> f1.transform {
        | case Success(a) => Success(a)
        | case Failure(_: MyException) => Success("a")
        | }
                       ^
          warning: match may not be exhaustive.
          It would fail on the following input: Failure((x: Throwable forSome x not in MyException))
   val res3: scala.concurrent.Future[String] = Future(<not completed>)
   
   scala> f2.transform {
        | case Success(a) => Success(a)
        | case Failure(_: MyException) => Success("a")
        | }
                       ^
          warning: match may not be exhaustive.
          It would fail on the following input: Failure((x: Throwable forSome x not in MyException))
   val res4: scala.concurrent.Future[String] = Future(<not completed>)
   
   scala> f2.onComplete {
        | case Success(a) => println(s"success :${a.toString}")
        | case Failure(b) => println(s"failure :${b.toString}")
        | }
   failure :java.lang.RuntimeException: bleh
   ```
   
   For the success case it would create a match error but as noted before those cases shouldn't occur for those specific parts of the code.


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