I'm having fun with some async code: ```) suspend fun detectTVOnSignal(tvState: MutableStateFlow&lt...

# coroutines

[reactormonk]

I'm having fun with some async code:

)
suspend fun detectTVOnSignal(tvState: MutableStateFlow<TVState>): TurnedOnDetectionHeuristics? {
    val result =  coroutineScope {
        val transientToOn = tvState.filter { it is TVState.TransientToOn }.produceIn(this)
        val on = tvState.filter { it is TVState.On }.produceIn(this)

        Timber.d { "starting select" }
        select<TurnedOnDetectionHeuristics?> {
            transientToOn.onReceive {
                Timber.d { "starting second select" }
                select {
                    on.onReceive {
                        Timber.d { "got transition and on" }
                        TurnedOnDetectionHeuristics.On
                    }
                    onTimeout(30.seconds) {
                        Timber.d { "only got transition" }
                        TurnedOnDetectionHeuristics.TransitionToOn
                    }
                }
            }
            on.onReceive {
                Timber.d { "got on" }
                TurnedOnDetectionHeuristics.On
            }
            onTimeout(30.seconds) {
                Timber.d { "timed out on on" }
                null
            }
        }
    }
    Timber.d { "Result: $result" }
    return result
}

I get:
• starting select
• got on
<nothing>
^ I'd expect the "Result" here.

[ephemient]

https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/produce-in.html does not terminate unless the flow does

[reactormonk]

I assumed select only picks and executes the first matching clause, which is then the result

[ephemient]

the select is done, but the coroutineScope is still alive because it has children (the launched produceIn jobs)

[reactormonk]

Oh, duh So gotta kill them first?

[ephemient]

also note that https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-state-flow/

State flow never completes.

[ephemient]

I mean this seems pretty contrived and a poor way to handle it to begin with

[reactormonk]

I'm always open to suggestions, got that one a while back

[ephemient]

there's no guarantee of ordering between the two collectors. just do it once

[reactormonk]

That's due to domain, maybe there's a TransientToOn signal, maybe not.

[reactormonk]

Or maybe I don't understand what you're getting at.

[ephemient]

val onOrTransition = withTimeoutOrNull(30.seconds) {
    tvState.firstOrNull { it is TVState.On || it is TVState.TransientToOn }
}
val on = if (onOrTransition !is TVState.On) {
    withTimeoutOrNull(30.seconds) {
        tvState.firstOrNull { it is TVState.On }
    }
} else {
    onOrTransition
}

[reactormonk]

That's... way simpler. I like it.

[reactormonk]

Thank you.