Add support for AbortSignal

[cheap-glitch]

Resolves #26
Blocked by jsdom/jsdom#3347

[fregante]

It might be because of the jsdom PR, but this PR is missing the only test change I'd expect:

• accept a signal

[fregante]

Let's merge this without waiting for jsdom. You can:

1. manually make the jsdom changes in your node_modules
2. ensure that the tests pass
3. mark these tests as test.serial.skip
4. commit
5. ...
6. profit

[cheap-glitch]

manually make the jsdom changes in your node_modules

Tried it but it's really tricky, there are some JS files generated from .webidl files and they're a mess, I have no idea what to change to make it work…

[fregante]

Unblocked by jsdom v20 🙂

[fregante]

Fin-ally!

[fregante]

Note to self: Before releasing this PR, I'll likely replace ArrayLike with Iterable so this can be a plain for-of (separate PR)

[fregante]

This feels like a micro-optimization that the engine can take care of since abort only happens once

Suggested change

	}, {
	once: true,
	});
	});

[cheap-glitch]

I added this because it was recommended by the Node.js docs, but I guess this is a browser package so it's probably superfluous 😅

[fregante]

It's out! Hope to see this used in RG soon, so we can test it out in production

https://github.com/fregante/delegate-it/releases/tag/v4.0.0

[stof]

shouldn't the delegated options be registered without any signal instead, as the ledger system can reuse an existing listener for multiple delegations ? Otherwise, aborting one of them would abort the native listener shared between them and so abort them all.

[fregante]

oof, you sounds right, but the tests pass. Are the tests broken?

From what I understand, you're saying that the ledger cannot deduplicate calls and therefore it has become useless/broken, but I think we have tests specifically to avoid duplicate registrations.

Can you suggest a piece of code that fails with v4 but passes with v3 to make sure we're talking about the same thing?

[fregante]

Ah I see what you mean. I think:

delegate(a, b, c, mysignal)
const controller = delegate(a, b, c);

controller.abort()

Currently the second call is deduplicated, so the listener is only registered once. This has one important consequence:

• the second call does not have any link to the previous listener, so calling abort does nothing

I think this happens any time, regardless of mysignal actually. 😟

[fregante]

Native events, like us, ignore the signal when deduplicating listeners:

controller = new AbortController()
controller2 = new AbortController()
document.addEventListener('click', console.log, {signal: controller.signal})
document.addEventListener('click', console.log, {signal: controller.signal})
document.addEventListener('click', console.log, {signal: controller2.signal})
document.addEventListener('click', console.log)

This only register's one listener.

The funny thing is that controller2.abort() does nothing while controller.abort() removes the event. Tested in both Safari and Chrome.

This means we're matching the native behavior. The only difference is that we explicitly return an AbortController that does nothing.

[fregante]

Neat. Not only do native events ignore the successive signals, but ignore future calls altogether!

document.addEventListener('click', console.log, {once: true})
document.addEventListener('click', console.log)

The handler is called once. That's it.

[stof]

ah, delegating different selectors does not share the ledger, so fine indeed.