Rule proposal: `no-return-await`

Please describe what the rule should do: Inside an async function, return await is useless. Since the return value of an async function is always wrapped in Promise.resolve, return await doesn’t actually do anything except add an extra tick before the overarching promise resolves/rejects. This pattern is almost certainly due to programmer ignorance of the return semantics of async functions.

What category of rule is this? (place an “X” next to just one item)

[ ] Enforces code style [ ] Warns about a potential error [x] Suggests an alternate way of doing something [ ] Other (please specify:)

Provide 2-3 code examples that this rule will warn about:

async function foo() {
  return await bar;
}

in favor of:

async function foo() {
  return bar;
}

Why should this rule be included in ESLint (instead of a plugin)? People are very anxious to use await, and will likely overuse it. This rule prevents a common hazard, and also helps educate developers about how async function works.

[shinout]

I found a case we need return await.

async function foo() {
  try {
    return await bar()
  }
  catch (e) {
    console.log(e) // error comes here
  }
}

async function fooWithoutAwait() {
  try {
    return bar()
  }
  catch (e) {
    console.log(e) // cannot catch async error
  }
}

async function bar() {
  throw new Error('bar')
}

foo() // catch error
fooWithoutAwait() // unhandled promise rejection

How can we manage these async exceptions?

[vitorbal]

I will 👍 this.