suspendCancellableTimeoutCoroutine() - cancelled by timeout 1. app crashes

runBlocking {

suspendCancellableTimeoutCoroutine()

}

2. app doesn't crash

runBlocking {

launch {

suspendCancellableTimeoutCoroutine()

}

}

3. app doesn't crash, but I don't see stacktrace in logcat

runBlocking {

val handler = CoroutineExceptionHandler { _, e -> e.printStackTrace() }

launch(handler) {

suspendCancellableTimeoutCoroutine()

}

}

4. This is the behavior that I have now, it works as needed

runBlocking {

try {

suspendCancellableTimeoutCoroutine()

} catch(e: CancellableException) {

e.printStackTrace()

}

}

Could anyone explain to me 2 and 3, please?

In 3, you already have an exception handler which means that the cancellation exception is consumed by the handler and that’s it. In 2, the

launch

coroutine consumes the cancellation exception and doesn’t propagate it to its parent (runBlocking). In 1, no one is consuming the exception so it ends up being propagated up the chain and unhandled exception = crash.

Thanks! So in 3 my

val handler

is not used because

launch

consumes the exception?

the other way around. your handler consumes the exception and launch just finishes gracefully.

But why I don't see stacktrace and breakpoint doesn't hit in 3?

Actually, I am wrong. Cancellation exceptions are ignored by handlers. See here for more info https://kotlinlang.org/docs/reference/coroutines/exception-handling.html#cancellation-and-exceptions

Thank you!