Abort watch with `AbortSignal`

[jimmywarting]

it would be nice if navigator.geolocation.clearWatch could cancel a watch when a AbortSignal gets aborted.
one single AbortSignal can be used to cancel a hole bunch of things

Having one and only AbortSignal per page (like in a single-page-application) is nice
the abort signal can be used to cancel ongoing fetch calls to APIs that is needed to view the page and so much more.
I use one abort signal that gets created at every time the history changes and for every API call i make i include that signal.
so if the user quickly just jump trough the history to go back 3-5 pages then i can abort what is being called to the api.

if the Geolocation had the possibility to cancel itself when a map isn't needed anymore when navigating away from a page with a map, than that would be awesome!

i propose the possibility of passing it along with the options

navigator.geolocation.clearWatch(success, error, { 
  signal: AbortSignal.timeout(x) 
})

that way we don't have to manually keep track of a index, and calling clearWatch when needed. it would just cancel itself upon a abort event

[reillyeon]

Wouldn't you add the AbortSignal to the watchPosition() call like this?

navigator.geolocation.watchPosition(success, error, {
  signal: AbortSignal.timeout(x)
});

The challenge is feature detection, because an implementation that doesn't support this would simply ignore the signal field and wouldn't ever clear the watch. Realistically, this is something that is trivial to polyfill:

function watchPosition(success, error, options) {
  { signal } = options;
  delete options.signal;
  const watchId = navigator.geolocation.watchPosition(success, error, options);
  if (watchId != 0) {
    signal.addEventListener('abort',
                            () => { navigator.geolocation.clearWatch(watchId); },
                            { once: true });
  }
}

This is a similar challenge to what we face when trying to update this API to return a Promise.

[jimmywarting]

Wouldn't you add the AbortSignal to the watchPosition() call like this?

yea, sorry that was what i meant^^
made a typo... (corrected it)

The challenge is feature detection

Hmm, did not even tough of that when posting this.
how about when you add a signal then you would not get any number id back?

const result = navigator.geolocation.watchPosition(success, error, { signal })
const supported = result === undefined
console.assert(result === undefined, 'calling watchPosition with signal should not return anything')

[reillyeon]

how about when you add a signal then you would not get any number id back?

You could, but then you still have to still include the feature detection code in your code so it would look like,

function watchPosition(success, error, options) {
  { signal } = options;
  const watchId = navigator.geolocation.watchPosition(success, error, options);
  if (watchId !== undefined && watchId !== 0) {
    signal.addEventListener('abort',
                            () => { navigator.geolocation.clearWatch(watchId); },
                            { once: true });
  }
}

There's a good argument to be made that eventually developers could rely on the new behavior once it has been available in all browsers for long enough so say, 5 years, after this ships the fallback code isn't necessary.