Hey I have a question:

fun main() = runBlocking {
    try {
        cScope()
    } catch (error: Throwable) {
        println(error)
    }
}

suspend fun cScope() = coroutineScope {
    val def = async { failure() }
    try {
        def.await()
    } catch (error: Throwable) {
        println(error)
    }
}

Why is it only possible to

catch

the error when wrapping

cScope()

and not

def.await()

?

When async throws an exception, it automatically cancels the scope, so you can't just catch the exception when retrieving. To be fair, I'm still not 100% sure how to properly catch errors, but adding an exception handler seems to be the best alternative

I see that the only way to catch them is via

supervisionScope

. But how can I handle this on Android using a

ViewModel

and implementing

CoroutineScope

. How can I there handle any exceptions without cancelling my scope forever?

When you define a new inner scope like in your code, the error should only propagate to that scope. You can also set an error handler (forgot the method name) within it. I do have the same problem with my code though, which I've asked in previous threads. I haven't had time to test but exception handler seems like the way to go. À supervisor scope adds a supervisor job to the scope, meaning that exceptions in children should not affect other children. I already have a supervisor in my top level scope though so I'm not sure if that alone is a suitable solution

If you use

supervisorScope

unhandled exceptions will affect other children. So if I change

coroutineScope

to it in my example and I remove the

try/catch

in the

fun cScope

then other children would be cancelled.

What's your test code example? The point of the supervisor is to disallow exceptions from propagating upwards. I might have to read more into the docs

This makes sense because it throws an exception. What I'm saying is that you probably won't need to wrap failure within async, whereas if you didn't have a supervisor scope the internal failure would have cancelled your scope even if you caught await

This is how coroutineScope works, thows an exception that cause of child coroutines to fail. To handle error just wrap call of coroutineScope to try/catch or use supervisorScope