How to cancel/unsubscribe from coroutines Flow

Question

I notice a strange behavior when trying to prematurely cancel from a Flow. Take a look at the following example.

This is a simple flow that emits integer values

Answer 1

I want to add that in 1.3.7 version emissions from flow builder now check cancellation status and are properly cancellable. So the code in question will work as expected

Answer 2

I came across a workaround in this related issue

I have replaced every single collect with a safeCollect function in my project:

/**
 * Only proceed with the given action if the coroutine has not been cancelled.
 * Necessary because Flow.collect receives items even after coroutine was cancelled
 * https://github.com/Kotlin/kotlinx.coroutines/issues/1265
 */
suspend inline fun <T> Flow<T>.safeCollect(crossinline action: suspend (T) -> Unit) {
  collect {
    coroutineContext.ensureActive()
    action(it)
  }
}

Answer 3

I came up with this recently

it seems that it will only actually cancel if it reaches a suspending point and in your code that emits there is no such point

to solve this either add yield() between emissions or some other suspending function like delay(100)