async/await improvements

Boris Zbarsky bzbarsky at mit.edu
Wed Nov 12 09:51:46 PST 2014


On 11/12/14, 9:49 AM, James Long wrote:
> Yes, I have (I work on the Firefox devtools). The best we can do (as
> far as I know) is log an error when a promise is GC-ed with an
> unhandled error

Note that this is what Firefox does right now, but we're moving away 
from that to a "report if the event loop starts spinning while a promise 
with an unhandled rejection is live" and "withdrawing" the report 
somehow if it then gets handled.

 > It doesn't help at
 > all for production (sure, "you aren't using promises correctly" and
 > all that, but not all programmers are perfect).

Note also Domenic's proposal at 
http://lists.w3.org/Archives/Public/public-whatwg-archive/2014Sep/0024.html 
in terms of production.  It does involve a bit more work on the part of 
sites that want to usefully do telemetry for this, of course.

> Also makes it harder for tests, because I don't think we've standardized an
> onUncaughtPromiseException, and if we have, it's GC-sensitive.

Domenic's proposal above is such a thing, and not GC-sensitive.

Now it does have the false positive problem you mention later in this 
thread, of course.

All of this is not directly related to async/await, except insofar as 
those are built on top of Promise.

-Boris


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