I need to implement `Delay.scheduleResumeAfterDela...

# coroutines

[Alexander Maryanovsky]

I need to implement Delay.scheduleResumeAfterDelay such that
1. The continuation runs in a certain CoroutineScope
2. I am able to query whether there are any continuations waiting to be resumed.
Currently we have something that looks roughly like this:

val delayedTasks = mutableSetOf<Runnable>()
    override fun scheduleResumeAfterDelay(timeMillis: Long, continuation: CancellableContinuation<Unit>) {
        val block = Runnable { continuation.resume(Unit, null) }
        delayedTasks.add(block)
        scope.launch {
            kotlinx.coroutines.delay(timeMillis)
            delayedTasks.remove(block)
            block.run()
        }
    }

but if someone launches a coroutine that delays (say for a long time) and then cancels the Job, this will not be notified that the coroutine was cancelled and will be stuck in delay until timeMillis runs out.
How do I do this correctly?

[Alexander Maryanovsky]

Maybe like this?

override fun scheduleResumeAfterDelay(timeMillis: Long, continuation: CancellableContinuation<Unit>) {
        val block = Runnable { continuation.resume(Unit, null) }
        delayedTasks.add(block)
        val job = scope.launch {
            try {
                kotlinx.coroutines.delay(timeMillis)
            } finally {
                delayedTasks.remove(block)
                block.run()
            }
        }
        continuation.invokeOnCancellation {
            job.cancel()
        }
    }