Hey, I’m working on a library that awaits some `Co...

# coroutines

[Syex]

Hey,
I’m working on a library that awaits some CoroutineScope as an input in order to launch some new coroutines. If any of these coroutines throw an exception it should delegate them to the initially given CoroutineScope. However, I figured out, if this scope has a SupervisorJob() all exceptions of my launched coroutines are just silently swallowed, which is probably working as intended.

Is there any way I still can crash the application? I tried to create my own scope via CoroutineScope(initialScope.coroutineContext + Job()) , but it still keeps the behavior of the supervisor job.

[tseisel]

You can try setting a CoroutineExceptionHandler in the context of the CoroutineScope associated with the SupervisorJob :

val exceptionHandler = CoroutineExceptionHandler { exception ->
  // Do something with the caught error
}

val scope = CoroutineScope(SupervisorJob() + exceptionHandler)

[tseisel]

Because I don't know much about coroutine exception handling (never really tried using SupervisorJob or CoroutineExceptionHandler), here is what the docs states about it: https://kotlinlang.org/docs/reference/coroutines/exception-handling.html#coroutineexceptionhandler

[Syex]

The CoroutineExceptionHandler is never triggered this way 😕

[streetsofboston]

I did some experimentation with CoroutineScopes and their exception handlers: https://link.medium.com/WPEB31h7F5

[Syex]

Great article 👍 I figured out my problem arose because it threw CancellationException which is ignored by CoroutineExceptionHandler 🙈

[rkeazor]

One question , if it's a library for other applications to consume. Why not just expose suspend functions with coroutine scope builder or use a flow

[rkeazor]

That way the client needs to manage the coroutineScope

[Syex]

use case is a little more complex. Usage is something like “post event x, lib does some things async in a coroutine, client listens to changes on a `Flow`”

[rkeazor]

So those the client give you event X than you post it ?

[rkeazor]

It still sounds possible

[rkeazor]

Have you tried this using a channelFlow?