Rule proposal: `no-nested-await`

Nesting await inside a statement often gets messy. It’s better to split the line using an intermediate variable.

This is potentially autofixable. The only issue is that this would need to generate a name for an intermediate variable.

Fail

const filtered = (await Promise.all(promises)).filter(Boolean);

Pass

const unfiltered = await Promise.all(promises);
const filtered = unfiltered.filter(Boolean);

[fisker]

We can start with property access and call expression, maybe add more cases in future.

[remcohaszing]

I think we need to determine which cases should be reported. Typically I think the ones wrapped inside parentheses should be reported.

// Function
console.log(await promise);
(await import('foo')).default;

The following may be acceptable due to the lack of a better alternative:

const foo = (await promise) as string;

The following look ok to me:

const { default: foo } = await import('foo');

console.log({
  foo: await fs.readFile('foo'),
  bar: await fs.readFile('bar'),
});