Add AbortSignal.abort() static method (FF88)

[hamishwillee]

Firefox 88 adds a new static method AbortSignal.abort().

• Gecko bug https://bugzilla.mozilla.org/show_bug.cgi?id=1698468
• Useful background: Creating an already aborted AbortController whatwg/dom#959 (comment)

BCD and Release notes in separate PR.

FYI @sideshowbarker

MDN tracking bug: #3460

[chrisdavidmills]

@hamishwillee Sounds plausible to me, from reading the background docs, but I'm not really sure I get it.

Therefore, paging @annevk , as he usually understands this kind of stuff way better than me. Anne, do you have time to give this content addition a very quick look over to see if it makes sense?

[hamishwillee]

@annevk When you have a moment, can you please sanity check as per #3616 (review)

[annevk]

The description seems somewhat wrong. This is a shorthand for:

const controller = new AbortController();
controller.abort();
return controller.signal;

The signal is something you pass to fetch() and other APIs, it's not something that is created there.

[hamishwillee]

@annevk Thanks, you're right.

I understand what this shorthand does, but not what scenario you would ever need to use it in. My understand is normally you create and pass in the signal to your fetch. As some point later you decide to abort (in this case following a timeout, but maybe following a button press).

const controller = new AbortController();
const signal = controller.signal;

setTimeout(() => controller.abort(), 5000);

fetch(url, { signal }).then(response => {
  return response.text();
}).then(text => {
  console.log(text);
});

Can you give me a real world example of when I might need to pass in an already cancelled signal to a fetch, ideally with a code fragment? Something along the lines of "I'm using fetch to get a resource, but X happens, so I need to pass in cancelled signal.

The various discussions on this had some info (which I paraphrased as below). That kind of explains why you might want to do this, but I don't really "get" the scenario that would make this useful.

[github-actions]

Preview URLs

• https://pr3616.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/AbortSignal
• https://pr3616.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/AbortSignal/abort
• https://pr3616.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/AbortSignal/aborted

Flaws

URL: /en-US/docs/Web/API/AbortSignal
Title: AbortSignal
on GitHub

No flaws! 🎉

---

URL: /en-US/docs/Web/API/AbortSignal/abort
Title: AbortSignal.abort()
on GitHub

No flaws! 🎉

---

URL: /en-US/docs/Web/API/AbortSignal/aborted
Title: AbortSignal.aborted
on GitHub

No flaws! 🎉

External URLs

URL: /en-US/docs/Web/API/AbortSignal
Title: AbortSignal
on GitHub

• https://developers.google.com/web/updates/2017/09/abortable-fetch (1 time)
• https://dom.spec.whatwg.org/ (1 time)
• https://mdn.github.io/dom-examples/abort-api/ (1 time)

---

URL: /en-US/docs/Web/API/AbortSignal/abort
Title: AbortSignal.abort()
on GitHub

• https://dom.spec.whatwg.org/ (1 time)

---

URL: /en-US/docs/Web/API/AbortSignal/aborted
Title: AbortSignal.aborted
on GitHub

• https://dom.spec.whatwg.org/ (1 time)

[annevk]

This would be more for a utility function that gives you the state of an operation as a signal. If the operation was already aborted, it would use this and not setup more complicated tracking. (The context was about code in Node.js, not directly related to fetch() I think.)

[hamishwillee]

@annevk Thanks, but whether it is used in a browser or node, it still isn't clear why you would ever need to pass an aborted signal for something that is already aborted?

So unless someone can provide a concrete example/reason for this, all I can do is what you said - which is say that it is a shorthand/utility function. Then wait for unanswerable questions on why we bothered :-0

[annevk]

I think it depends on how you organize your code, but if you already have logic to deal with an aborted fetch and you want to trigger that logic if another operation got aborted (from which you obtained a signal), it might well make sense to pass the aborted signal on to the fetch, which will then trigger the aborted fetch logic.

[annevk]

Thanks for tackling this! This looks good to me.

[hamishwillee]

Thanks @annevk - appreciate your patience!

@chrisdavidmills I think this is good to go. It isn't particularly "rich content" but I think now enough for anyone who has constructed their code in such a way that this is useful, to understand how it can be used.

[chrisdavidmills]

Thanks @annevk - appreciate your patience!

@chrisdavidmills I think this is good to go. It isn't particularly "rich content" but I think now enough for anyone who has constructed their code in such a way that this is useful, to understand how it can be used.

Thanks for the help @annevk , and cheers for the perseverence @hamishwillee . This was a tricky one, and I think you've handled it well.