Convert java Optional to Kotlin Arrow Option

Question

What would be the best way to convert Java Optional to Arrows Option? I was expected to have something out-of-box, but it's not there. Something like:

fun <T> Optional<T>.toOption(): Option<T> = if (this.isPresent) Some(this.get()) else none()

Answer 1

There is no such function at the moment, but such a contribution would be welcomed!

Arrow however does not recommend using Option unless absolutely necessary. The only use-case being nested nulls, which is the limitation for ReactiveX implementation of RxJava & Project Reactor. Both libraries don't allow null being used for their generic value A in Flowable, Flux, Mono, etc.

Analogue, you cannot use null as an empty signal for generic code in Kotlin. Unless A is constraint to be non-null by using A : Any.

Only in both cases should you use Arrow's Option, otherwise using Kotlin's nullable type is recommended by the Arrow maintainers.