I have the following block of code ``` scope launch

Question

I have the following block of code ``` scope launch <http Dispatchers IO|Dispatchers IO> val result = runCatching fetcher key receiverChannel send key to result ``` The scope is currently `GlobalScope` and `fetcher` is a suspended function that just returns an exception Even with runcatching I m getting ``` FATAL EXCEPTION DefaultDispatcher worker 4 java lang RuntimeException Test ``` Is there something else I m missing Do I need to add a new scope here

octylFractal · Answer

what s the stacktrace look like

Allan Wang · Answer

This is how it runs on a clean test which just waits on a single completable that should return the fetched result ``` Exception in thread DefaultDispatcher worker 1 coroutine 3 java lang RuntimeException Crash key at com pitchedapps frost kotlin FlyweightTest$before$1 invoke FlyweightTest kt 51 at com pitchedapps frost kotlin FlyweightTest$before$1 invoke FlyweightTest kt 32 at com pitchedapps frost kotlin Flyweight$fulfill$1 invokeSuspend Flyweight kt 126 at kotlin coroutines jvm internal BaseContinuationImpl resumeWith ContinuationImpl kt 32 at kotlinx coroutines DispatchedTask run Dispatched kt 233 at kotlinx coroutines scheduling CoroutineScheduler runSafely CoroutineScheduler kt 594 at kotlinx coroutines scheduling CoroutineScheduler access$runSafely CoroutineScheduler kt 60 at kotlinx coroutines scheduling CoroutineScheduler$Worker run CoroutineScheduler kt 742 java lang RuntimeException Crash key at com pitchedapps frost kotlin FlyweightTest$before$1 invoke FlyweightTest kt 51 at com pitchedapps frost kotlin FlyweightTest$before$1 invoke FlyweightTest kt 32 at com pitchedapps frost kotlin Flyweight$fulfill$1 invokeSuspend Flyweight kt 126 at |b|b|b Coroutine boundary |b |b at kotlinx coroutines CompletableDeferredImpl await CompletableDeferred kt 64 at com pitchedapps frost kotlin FlyweightTest$error$1 invokeSuspend FlyweightTest kt 102 Caused by java lang RuntimeException Crash key at com pitchedapps frost kotlin FlyweightTest$before$1 invoke FlyweightTest kt 51 at com pitchedapps frost kotlin FlyweightTest$before$1 invoke FlyweightTest kt 32 at com pitchedapps frost kotlin Flyweight$fulfill$1 invokeSuspend Flyweight kt 126 at kotlin coroutines jvm internal BaseContinuationImpl resumeWith ContinuationImpl kt 32 at kotlinx coroutines DispatchedTask run Dispatched kt 233 at kotlinx coroutines scheduling CoroutineScheduler runSafely CoroutineScheduler kt 594 at kotlinx coroutines scheduling CoroutineScheduler access$runSafely CoroutineScheduler kt 60 at kotlinx coroutines scheduling CoroutineScheduler$Worker run CoroutineScheduler kt 742 ``` Not sure why it ends up being logged three times

Allan Wang · Answer

Code <https github com AllanWang Frost for Facebook blob dev app src main kotlin com pitchedapps frost kotlin Flyweight kt> Test ``` Test fun error runBlocking flyweight fetch CRASH KEY await ``` I m trying to debug something where the log seems to be erased due to coroutines but I think it s related to this problem here

octylFractal · Answer

looks tricky not sure why it s going wrong I d probably need to look at the class files neutral face

Allan Wang · Answer

The actual problem I have is way weirder I have a suspend function that is called with an io dispatcher I m calling my flyweight which doesn t deal with the main thread at all and then returning something If the flyweight fails I get a problem that I called an action without a looper which in android implies that I called a ui action on a worker thread However if the flyweight succeeds or if I replace the flyweight call with a `throw` everything is fine And given I have no line numbers for the error and this only occurred when I switched from rx to coroutines I know it s something wrong with how I rewrote it