Is it really correct that this code: ```withContex...

# coroutines

[ansman]

Is it really correct that this code:

withContext(Dispatchers.Unconfined) {
   println(1)
   withContext(Dispatchers.Unconfined) { // Nested unconfined
       println(2)
   }
   println(3)
}

can really print 1, 3, 2? If the inner withContext was a launch I'm fully on board with the fact that the order is undefined. But since withContext actually returns something it would mean that this code:

withContext(Dispatchers.Unconfined) {
   val result = withContext(Dispatchers.Unconfined) { 1 + 1 }
   println(result)
}

Could be broken?

[Sam]

What makes you say that it could print 1, 3, 2? Have you seen that claim made somewhere? Since there are no calls to launch or async, I think your reasoning is correct and this code should execute sequentially.

[ansman]

From the kdoc for `Dispatchers.Unconfined`:

For example, the following code:
withContext(Dispatchers.Unconfined) {
   println(1)
   withContext(Dispatchers.Unconfined) { // Nested unconfined
       println(2)
   }
   println(3)
}
println("Done")

Can print both "1 2 3" and "1 3 2", this is an implementation detail that can be changed. But it is guaranteed that "Done" will be printed only when both withContext are completed.

[Sam]

Huh. I agree with you, that documentation does not match my understanding of how withContext works.

[ansman]

I'm feeling fairly sure that they meant to use launch in their example

[ansman]

Filed an issue https://github.com/Kotlin/kotlinx.coroutines/issues/3605

[Nick Allen]

Yeah, that been wrong for years now. https://youtrack.jetbrains.com/issue/KT-47032/Incorrect-code-example-for-Dispatchers.Unconfined-in-kotlinx.coroutines-docs

[ansman]

My PR that fixes this just landed

[Sam]

😬 just a bit later on it still refers to “both withContext calls” though.

[Sam]

I’m not sure what the wording for that should be after the change.

[ansman]

Damn, I missed that. Will fix

[ansman]

https://github.com/Kotlin/kotlinx.coroutines/pull/3615