Hmm, why is

Flow.firstOrNull

restricted to non nullable types? Feels like it'd be useful even with flows with nullable types?

If it were used on a nullable flow, when that method returns you have no way of knowing if it was because the Flow emitted a null value, or if the flow closed without emitting anything. In the first case,

null

is a valid value, while in the second case,

null

is a signal of an error

Right, but that's up to the caller to decide if they want that or not

Almost no one wraps values in optionals in Kotlin. You can use

transformWhile

for your use case.

For what use case? Getting the first element or null?

firstOrNull for nullable types.

I still don't understand what you mean by that

My two sentences were two distinct statements. Here's a snippet to illustrate my second statement:

fun <E> Flow<E>.firstOrNullForNullables() = transformWhile {
    emit(it)
    false
}

Implementing this operator is trivial and that isn't what I'm asking for here

You make a point with the

List

version. Might make sense to submit the API change request in GitHub issues then. Good news is that is should be binary compatible if it's accepted.

I opened an issue here: https://github.com/Kotlin/kotlinx.coroutines/issues/2229