Task queue completions before parent completions in v8

[guybedford]

In the following test case:

a.js

console.log('a start');
await 0;
console.log('a end');
Promise.resolve().then(() => console.log('a after'));

b.js

import './a.js';
console.log('b start');

The execution in v8 follows:

a start
a end
a after
b start

Can we verify this is the expected order per this spec, including ensuring test262 coverage of the case?

[robpalme]

The currently implemented ordering seems inefficient. There's no reason to delay evaluation of the b.js. Meaning ideal ordering would be:

a start
a end
a after
b start

[sokra]

I think it makes kind of sense if you see an async module similar to an async function.

With an async function there is also a micro-tick between the last line and any work that follows after that.

(async () => {
  console.log('a start');
  await 0;
  console.log('a end');
  Promise.resolve().then(() => console.log('a after'));
})().then(() => { console.log('next stuff'); });

[guybedford]

Agreed the async wrapper analogy makes sense and fits intuition. The behaviour definitely matches the spec as well, I just found it a little surprising to see in these test cases. Closing.