This is a good point. I didn't think about passing the same callback more than once.
Ideally, if the same resolve & reject callback combination is passed more than once, the same promise is always returned (I can't think of a use case where promises could stop to work, if promises were specced with this additional rule, but maybe I overlooked). So if we pretend that's the case, it seems ignore() should deregister all callbacks. Do you have a use case where the same callback will be passed to the same promise more than once? Does deregistering all callbacks at once seem counter-intuitive in that case if you want to show disinterest? Another way out is to make ignore() cancel then() in a LIFO manner, probably also provide a ignoreAll(), which also gives a hint that ignore() only ignore one callback combination a time. But this just seems ugly. > On Aug 3, 2015, at 11:49 PM, Boris Zbarsky <[email protected]> wrote: > > On 8/2/15 8:43 PM, Glen Huang wrote: >> You can think it as that each promise keeps a list of its child promises, >> when the same callback is passed to .ignore() it sets a flag on the >> corresponding child promise so that when itself resolves/rejects, it won't >> pass that state to that child promise > > There seems to be a potential footgun here. Say I call then() twice with the > same function. Now I have two child promises. If I now call ignore() with > that function, which of the child promises is ignored? Both? Just one of > them? Something else? > > This situation doesn't _quite_ arise with add/removeEventListener, because > you can't addEventListener a given listener twice to the same event target. > So a removeEventListener can see at most one matching listener. > > -Boris > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
