Promise.fold()

[oltrep]

Closes #46

As discussed in the issue, here is the PR for Promise.fold!

Let me know if you have any comments/improvements :)

[jhampton]

Thank you @oltrep! I'm curious - is there a cancellation behavior that needs to be supported here from the reference implementation (or to align with the other utilities in this library).

[evaera]

Thank you for the PR! I will review this next week. I'm on vacation this week

[evaera]

Thanks for the PR. I have requested some changes. Notably, we should always return a Promise from Promise.fold, so as to be in accordance with the other functions and for consistency.

You can take advantage of chaining so you don't have to inspect the values directly: https://eryn.io/roblox-lua-promise/lib/Tour.html#chaining

This function also has no cancellation semantics. You can read about cancellation here: https://eryn.io/roblox-lua-promise/lib/Tour.html#cancellation

If we instead implement Promise.fold over top of Promise.each, we get those cancellation and chaining semantics for free. How does that sound?

Thanks again!

[oltrep]

I think I've addressed all your comments, let me know if you find something else :)

[evaera]

Thanks for your contributions! Looks good.