Hi, can anyone show me how to wait for a deferred ...

# coroutines

[Justin Tullgren]

Hi, can anyone show me how to wait for a deferred with a timeout but allow the deferred to continue without a cancellation or timeout exception from the surrounding context?

[Justin Tullgren]

What I thought would work

[Joffrey]

val deferred = TODO("whatever gives you the deferred, maybe an async{} call")
val value = withTimeoutOrNull(1000) { deferred.await() }
if (value == null) {
    // handle the timeout
} else {
    // use the deferred value
}

[Justin Tullgren]

try {
  withTimeout(5000) {
    deferred.await()
  }
catch(t: TimeoutException) {
  emit(TimedOut) // let people know to use cache
  val finishedResult = deferred.await()
  emit(finishedResult)
}

[Justin Tullgren]

will withTimeoutOrNull cancel the deferred though? Thats what i am getting as an exception, that I am trying to do something in a cancelled context violating exception transparency

[Joffrey]

No it doesn't cancel the deferred, it only cancels the suspending functions inside its own block { ... } (so the await call in this case), but the deferred itself is controlled by whatever scope you ran it with:
https://pl.kotl.in/AW8gJcbu_

[Justin Tullgren]

okay thanks, i'll mess around with my solution then

[Joffrey]

Note that your solution also should work. Maybe something else is wrong for you:
https://pl.kotl.in/C6c8KzzZL

[Justin Tullgren]

ya thats what i am thinking