feat(eslint-plugin): added new rule await-promise

[JoshuaKGoldberg]

Adds the equivalent of TSLint's await-promise rule.

[codecov]

Codecov Report

Merging #192 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #192      +/-   ##
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+ Coverage   96.95%   96.96%   +0.01%     
==========================================
  Files          71       72       +1     
  Lines        2694     2705      +11     
  Branches      435      436       +1     
==========================================
+ Hits         2612     2623      +11     
  Misses         49       49              
  Partials       33       33

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/await-thenable.ts	100% <100%> (ø)

[JoshuaKGoldberg]

Btw, this ended up using the same containsType(ByName) util as #194, so I moved it to utils/types.js.

[bradzacher]

code LGTM

[JamesHenry]

Apologies for the conflicts, we decided to remove the counts from the ROADMAP here: #225

They are too awkward to maintain manually, so this is the last time you will have to deal with syncing that up!

[JoshuaKGoldberg]

Awesome, glad the type checker works out that way! That looks like it'll need to be a shared method by this, #194, and other promise-checking functions.

Would you still want the allowedPromiseNames option as part of the rule? I can't think of a way for it to be particularly useful unless folks have improperly written Promise-like typings, so I'll add test cases for definitions mirroring Bluebird's and other popular polyfills.

[mysticatea]

Would you still want the allowedPromiseNames option as part of the rule?

I don't think so.

And, I think we should rename the rule to require-await-thenable.

• In practice, Rules which disallow arbitary notation if something is lacking have require- prefix.
• Now the rule checks then property rather than Promise.

[JoshuaKGoldberg]

Turns out tsutils already has a isThenableType method, so I used that one and removed allowedPromiseNames. ✔

require-await-thenable

👍 on promise -> thenable, but I'm still hesitant to sustain the require- prefix tradition for similar reasons to the no- prefix tradition:

• it's rather inconvenient to work with larger eslintrc files when the names' alphabetical ordering isn't very useful
• it's hard to tell when rules will eventually allow the opposite of the require- behavior; for example, if this rule eventually also handles whether we should or shouldn't await values of type any and/or unknown
• require- has a naming relevancy to require() and modules, which is confusing for newcomers to look at

I don't want to bikeshed in your repository (especially if the focus is to adhere to existing ESLint traditions) 😄 so if you'd like I can rename to require-await-thenable in this PR! Just a couple of cents.

[merlinnot]

Hey guys, is it still blocked? It looks like the TS migration is done.

[JamesHenry]

@mysticatea @j-f1 please can you update your reviews of this PR?

Probably worth just getting it in at this point!

[mysticatea]

I'm sorry for my disappeared. I have lost track in busy of working for ESLint 6.

I left some fixes and suggestions.

[JamesHenry]

Perfectly understandable @mysticatea! Thanks for looping back to it.

Looks like @JoshuaKGoldberg addressed your most recent feedback, would you agree?

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