Node: Should domains catch `unhandledRejection` events

[vdeturckheim]

• Version: future
• Platform: any
• Subsystem: domain

I have been thinking about this for a while and now that domain API relies on Async Hooks, it would probably make sense by symmetry to catch unhandledRejection events in domains.

d.run(() => {
    throw new Error() // this will be caught
});

but

d.run(await () => {
    throw new Error() // this will not be caught
});

What is your take on this? I might be missing some previous discussions on that topic, sorry if it's the case :angel: .
cc @nodejs/domains @mmarchini

[mmarchini]

cc @nodejs/diagnostics

[mcollina]

I am -1 to do anything to domains. I think we should remove them as soon as async_hooks exits experimental. Ideally we could still maintain a userland implementation of them (they are implemented on top of async_hooks anyway).

[AyushG3112]

-1. domain is doc-only deprecated anyways(https://nodejs.org/api/domain.html), and I believe we should avoid it.

[ofrobots]

I'm -1 on changes to domains at this point. They are a dangerous and problematic API. I think we need them around for a while so that people can migrate to async-hooks or other higher level alternatives.

[vdeturckheim]

I get your points but I still feel we could go further here:

• domain is pretty much already an "over async hooks alternative", externalization should not be hard at this point
• if we externalize, we will add new features (at least I will try to do it) and maintain it, so if we do it later, why not doing it now?

At this point, domains are still used a lot (I know a handful of new projects which rely on them).

[AndreasMadsen]

Ideally we could still maintain a userland implementation of them (they are implemented on top of async_hooks anyway).

We are almost there, but there is one feature we can't support and we need another semver major release (node.js 11) before we can remove support for that feature. See DEP0097.

This feature addition makes sense to me, the only reason why it shouldn't be added is that we wish to remove domains. If we declare make an official effort to move domain to a userland module in node.js 11 or 12, then I don't see an issue with this feature.

[apapirovski]

Something that hasn't been discussed is the fact that we rely on the domain module extensively within the REPL. It'll take a lot of work to change that.

[vdeturckheim]

Closing as this will probably not happen.