A modern programming language that makes developers happier.

kotlinlang

At what point do you decide on using an Option over a nullable type?

I think it was there for some java support, but within kotlin I would always use nullability

TL;DR _nested nullability_, and it's always the same problem. Java inherently has this problem, and often results in false negatives as well.

All generics from Java are constraint to `Any?`, not `Any` so everything generic is _nullable_ but when inserting a `Int?` you get a _nested null_. Project Reactor, and/or RxJava, choose to use `null` as an internal optimisation mechanism and as a result they do not allow `null` as a value for `T`. There you have to resort to `Option` or Java's `Optional` to allow such a pattern of absent values.

However, in Kotlin (and with KotlinX Flow) this is never really needed. In generic code you can avoid this problem, or work around it.

Here is an in detail explanation on the website, <https://arrow-kt.io/learn/typed-errors/nullable-and-option/>