New rule: Disallow assignments that can lead to race conditions due to usage of await or yield (require-atomic-updates)

[feross]

https://eslint.org/docs/rules/require-atomic-updates

This was surprising to me. Apparently the following code contains a race condition:

let totalLength = 0;

async function addLengthOfSinglePage(pageNum) {
  totalLength += await getPageLength(pageNum);
}

Promise.all([addLengthOfSinglePage(1), addLengthOfSinglePage(2)]).then(() => {
  console.log('The combined length of both pages is', totalLength);
});

Ecosystem impact: Only one repo failed. Looks to be a false positive. Reported here: eslint/eslint#11954 This carries some amount of false positive risk (at least based on what I've seen on the eslint tracker). I'd like to enable this in standard 13 and see how it goes. We can relax this rule if there are too many false positives.

[Lonniebiz]

@feross

Take a look at this false positive:
eslint/eslint#11967

[feross]

Given the false positive reported by @Lonniebiz in #1320 and the reports coming in on the ESLint repo here (eslint/eslint#11899) I'm going to disable this rule for the standard 13 release out of an abundance of caution. We can revisit it again later once it's had some more kinks worked out.

Issues to watch:

• require-atomic-updates false positive eslint/eslint#11899
• require-atomic-updates reports false positive in finally block eslint/eslint#11954