Add swallowedRejection event to eventually replace multipleResolves

[dead-claudia]

What is the problem this feature will solve?

I need to be able to capture and log errors that are swallowed by the likes of Promise.all and Promise.race. multipleResolves currently fills that gap, but #41554 is deprecating the hook as it didn't really pan out.

What is the feature you are proposing to solve the problem?

A swallowedRejection hook fired any time a source promise to Promise.all/Promise.race rejects after the returned promise settles. This would not fire on multiple resolutions, avoiding performance impact there.

What alternatives have you considered?

1. Pushing for Deprecate multipleResolves? #41554 to be reversed. Obviously, that's not going to happen, so I didn't even bother trying.
2. Getting new Promise.* methods to replace the above ones.

[bnoordhuis]

For my understanding: you're interested in the second (or third, or...) source promise to Promise.all() or Promise.race() that rejects? Because you already know the first rejected promise, of course.

I don't think V8's promise hook mechanism is specific enough to scope it to just Promise.all() and Promise.race(). You said "the likes of" - what other sources are you thinking of?

[benjamingr]

The problem with multipleResolves is that it "didn't work right".

I'm not sure where people are expected to use what you're suggesting given that Promise.all/Promise.race explicitly have this "ignore further rejections" behavior and there are methods (like allSettled or any) that don't.