This week, my version of how to race coroutines in Kotlin. I think the ability to customize the race...

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[Sam]

This week, my version of how to race coroutines in Kotlin. I think the ability to customize the race with operators like filter() makes channelFlow() an amazing solution for this. https://medium.com/@sam-cooper/custom-kotlin-coroutine-races-77161141b2ac

[Sam]

The first place I saw this technique was in this comment from Louis Wasserman—does anyone know if it's been used in the wild before that?

[Alejandro Serrano.Mena]

you may already be aware of this, but the Arrow library provides race operations out of the box https://arrow-kt.io/learn/coroutines/parallel/#racing

[Sam]

Yeah, I think I have used the Arrow raceN function before 👍. Can it express something like raceNotNull, though? That extra customizability is the reason I really love the channelFlow method.

[Sam]

I'll add the mention of Arrow to my article either way, that's a good call

[Alejandro Serrano.Mena]

Can it express something like raceNotNull, though?

no, but you have given me an idea for a new function 😄

[Sam]

😄 maybe you can implement it with a channelFlow 😉

[louiscad]

Interesting, you found a shorter version than mine that depends on select!

Here's my article from 2021 and the code is here.

I think you might want to forward the CoroutineScope receiver of launch in the lambdas.

[Sam]

I can't take credit for the idea, I borrowed it from Louis Wasserman: https://github.com/Kotlin/kotlinx.coroutines/issues/2867#issuecomment-1458487275. I like your article, I think I even linked to it in the comments on my post!

[Sam]

Forwarding the coroutine scope receiver is a nice suggestion, but I think in this case I marginally prefer it without… the user can still use a coroutineScope() block inside their task, after all

[louiscad]

I prefer to reduce nesting, but I understand you would want to leave it out