Is there an idiomatic way to wait until a job is active? When I collect a hot flow it can be the cas...

# coroutines

[Arjan van Wieringen]

Is there an idiomatic way to wait until a job is active? When I collect a hot flow it can be the case that between the ‘launchIn’ of the collect and a new emission to the hot flow the collector job hasn't started. Assume I have no ownership over the replay :)

[Joffrey]

Do you have this problem in real life or in tests? If the latter, you should use utilities like `kotlinx-coroutines-test`'s runCurrent or advanceUntilIdle to ensure your coroutines have progressed enough

[Arjan van Wieringen]

In real life. In tests I have it working with runCurrent indeed.

[Joffrey]

Ok got it. In any case, using launchIn, the job is likely active from the start, but that doesn't mean it reached the suspension on the collect - so it would be of no use to you to wait for this event even if you could

[Joffrey]

Maybe you could do launch(start = CoroutineStart.UNDISPATCHED) { flow.collect { ... } } instead of using launchIn. That would ensure the first suspension point is reached

[Arjan van Wieringen]

I'll try that, thanks!

[Arjan van Wieringen]

You've been ridiculously helpful to me in the last days. Thanks!

[Joffrey]

Glad to hear! I'm happy to help 🙂 Btw sorry I didn't reply on your last post afterwards, I was on mobile and I couldn't really write any code or test anything

[Arjan van Wieringen]

Haha no worries. You've been incredibly helpful.

[Adam Powell]

https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/on-subscription.html can be useful as well

[Nick Allen]

onSubscription does not help here. It waits for the subscription on the SharedFlow to be setup so if an event is emitted, it won't be missed but it does not wait for the suspension point on collect so the “shared" coroutine may not have done anything.