fix(types) Correct overload order for act without strictNullChecks in TypeScript

[andyrooger]

What:

Correct the TypeScript definitions, so that we produce the correct return type for act(...) calls when strictNullChecks is turned off.

Why:

Take the following code

import { act } from '@testing-library/react-hooks'

const result = act(() => Promise.resolve())

With strictNullChecks turned on, the type of result is Promise<undefined> as you would expect.
Turn strictNullChecks off, and the type of result is now void.

This is particularly highlighted in my case as the project I'm working on has eslint rules that will complain if we try to await a value it thinks is not thenable.

How:

It seems the issue is that with strictNullChecks, the two overloads for act(...) do not have a lot of overlap so the order we specify them in doesn't matter. Without strictNullChecks, anything that matches the async overload also matches the sync overload. Since the sync overload is specified first, it is always chosen.

I've just swapped the overloads around so that the more specific one with Promises is checked first.

Checklist:

• Tests
• Ready to be merged
  
• Added myself to contributors table
  

[andyrooger]

@mpeyper I've followed the contributors doc for this, but it looks like you're using a bot for adding contributors now. Do I need to strip that change out?

[joshuaellis]

No you don't, the bot is just to help us if someone forgets!

[codecov]

Codecov Report

Merging #622 (146b04a) into main (18f7913) will not change coverage.
The diff coverage is n/a.

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  Coverage   100.00%   100.00%           
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  Files           15        15           
  Lines          218       218           
  Branches        26        26           
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  Hits           218       218           

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[mpeyper]

Thanks @andyrooger, I can see there is actually a note about this very issue in react's own types for act.

[andyrooger]

@mpeyper so they do! That could have saved me the long explanation. Thanks for the merge :)

[github-actions]

🎉 This PR is included in version 5.1.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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