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How can I cancel flow collection from within the `collect{}` operator? The docs say that it should be possible to call `cancel()` , but that doesn’t seem to work….

Where is the `cancel()` coming from in that case? :thinking_face:

`throw CancellationException` is the first thing that comes to mind, which then _probably_ ends up in a `launch` or `launchIn` and then the behavior depend on the surrounding `CoroutineScope` impl.

What is your use-case for this?

Ahh, okay, the docs use `runBlocking{}` , and there we have `coroutineScope` as receiver, on which cancel can be called.

<https://kotlinlang.org/docs/flow.html#flow-cancellation-checks>

However I wonder why there is a crash in this case when a `CancellationException` is thrown :thinking_face: Aren’t `CancellationExceptions` special kind of exceptions that don’t lead to crashes?

runBlocking needs to throw because it can return a result which won't be available if the coroutine is  cancelled

It's important to cancel and use "ensureactive" on the emitter, if you don't do that, you can cancel and flow still send

You can also compose this after the fact by calling `cancellable` it will inject `ensureActive()` in between calls to `emit`.
<https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/cancellable.html>