Missing helper (or am I missing something?)

[pckilgore]

First thank you for this library, it's been a joy to work with over Js.Promise.

A question: I feel like I'm constantly reaching for functions of signature:

let tryIfOk: (Future.t(Belt.Result.t('c, 'b)), 'c => Belt.Result.t('a, 'b)) => 
  Future.t(Belt.Result.t('a, 'b))

let tryIfErr: (Future.t(Belt.Result.t('b, 'c)), 'c => Belt.Result.t('a, 'b)) => 
  Future.t(Belt.Result.t('a, 'b))

Is there a simple way to compose this out of other functions already provided? It seems like no matter how I go about this in my code I'm doing a lot of ugly manual wrapping (which does work, it just feels extremely inelegant).

Thank you!

[scull7]

You can achieve a similar result if you "lift" your function into a future.

let lift: ('c => Belt.Result.t('a, 'b), 'c) => Future.t(Belt.Result.t('a, 'b));

let lift = (fn, c) => Future.value(fn(c));

let futureResult = someFuture -> Future.flatMapOk(lift(myFn))

But yes, I think I agree that this is missing a function. Possibly named andThen as I've done here:
https://scull7.github.io/bs-result/api/Result_promise.html#value-andThen

[pckilgore]

Interesting, thanks. Funny enough I'm using something a bit different, never really thought hard if I had made a poor trade-off (other than limited re-usability over composing with lift).

let andIfOk = (fut, f) =>
  Future.map(fut, res => Belt.Result.flatMap(res, f));

Happy to chip in a PR for discussion if there is some consensus around adding a new function.