AjaxObservable: complete subscribers on abort

[OliverJAsh]

Description:
It is possible for an XHR to be aborted externally, for example when the machine loses connectivity.

Currently, when the XHR is aborted in this way, the subscription remains.

In this case, I think we would want to complete the observable? Although it might also be useful to emit something to indicate it was aborted.

[cartant]

Are you sure that the onabort event fires for anything other than an abort call? My reading of the whatwg spec is that the aborted flag can only be set via a call to the abort method.

[OliverJAsh]

I tested it and the event was called when abort occurred due to sleeping my computer.

[cartant]

I'm wondering if the behaviour differs between browsers and also if it differs depending on whether a connection is severed or cannot be established in the first place.

In any case, if onabort is to be wired up, I think it should see the observable error, rather than complete.

That's my two cents. I'll be interested to hear what others think about this.

[kwonoj]

Interesting. it doesn't look like ng/http handles onAbort as well: https://github.com/angular/angular/blob/master/packages/common/http/src/xhr.ts so far I give a quick peek.

What other libs does? if it's promise based, does it reject / or not handling, etcs? My immediate feeling is also this maybe error cases.

[OliverJAsh]

if it's promise based, does it reject / or not handling, etcs?

I just attempted the same thing with fetch.

http://output.jsbin.com/kelayinizo/quiet makes a request that takes 10 seconds to complete.

If I sleep my computer in that time, here is what I find when I return:

Uncaught (in promise) TypeError: Failed to fetch

[benlesh]

I would think the error event should fire on the XHR with readyState 0. Is that not the case?

[benlesh]

complete is a signal of successful completion. This isn't correct. If it's aborted, it did not complete successfully.

[benlesh]

I can't approve this one, because I don't think it's the right approach.

[OliverJAsh]

Thanks for the review @benlesh, I agree it should emit error instead of complete, like fetch does.

I would think the error event should fire on the XHR with readyState 0. Is that not the case?

In my testing, the observable does not emit anything, so I guess no.

I'll update this PR to emit an error when the abort event is received?

[OliverJAsh]

@benlesh This is still a bug. Could you reply to my previous comment? I'm happy to contribute

[OliverJAsh]

Moved to #4251