feat: Add unwrapOrElse

[sya-ri]

Similar to unwrap, but returns default value by function: #587

const myResult = err('Oh noooo')

const multiply = (value: number): number => value * 2

const unwrapped: number = myResult.map(multiply).unwrapOrElse(() => 10)

const unwrapped: number = await errAsync(0).unwrapOrElse(() => 10)
// unwrapped = 10

Useful for lazily evaluating defaults or performing processing.

unwrapOrElse exists in Rust:
https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap_or_else

[changeset-bot]

🦋 Changeset detected

Latest commit: 05f1515

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
neverthrow	Minor

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[macksal]

reading this was a little confusing because of the err function in the library :)

[sya-ri]

Indeed. Rereading, I was confused too 😆

I made it better 😉

0f34663

[macksal]

I still find the naming err to be a bit confusing, but now I see that it's used everywhere for this type of argument 🤷🏼 e.g. in match directly below. no reason to break that pattern...

[macksal]

I think it's part of unwrapOrElse's contract to not call the callback for an Ok value.

It could make sense to test that (using jest.fn and expect(...).not.toHaveBeenCalled())

[supermacro]

See comments in #587