1) The [[Invoke]] operation is meant to primarily trap method calls generated by user-code of the form |obj.m(...args)|. This is by far the most common case, and I believe we should not extend [[Invoke]] with additional arguments that are irrelevant to this primary use case. Rather than having a boolean argument, better to statically separate the cases into two separate internal methods.
2) There are a number of places in the spec where [[Invoke]] should be called conditionally, if we know for sure the property is callable. Currently the pattern for this is [[Get]]+[[Call]]. We cannot refactor to [[Has]] + [[Invoke]] in general, because [[Has]] will return true also for non-callable values. If we believe these are call-sites where it is worth avoiding the allocation of a function, then having an additional internal method like [[GetMethod]] or [[InvokeConditional]] makes sense, but I doubt it's worth the added complexity. 3) For proxy trap invocations I maintain we are still better off with [[Get]] + [[Call]] to keep double-lifting as simple as possible. Cheers, Tom 2013/9/11 Till Schneidereit <[email protected]> > On Wed, Sep 11, 2013 at 4:44 AM, Brendan Eich <[email protected]> wrote: > >> Except http://ariya.ofilabs.com/2011/**08/hall-of-api-shame-boolean-** >> trap.html<http://ariya.ofilabs.com/2011/08/hall-of-api-shame-boolean-trap.html> >> . >> > > So one thing we could potentially do is to say that a proxy trapping > [[Invoke]] either always returns [invokeSuccess, result] and doesn't need > the boolean argument - or it's just never conditional: if you trap > [[Invoke]], you have to serve all method calls, and Proxy.[[Invoke]] would > just return result. Given that proxies users would most likely not be used > for these corner cases in the majority of cases, and quite deliberately so > in the others, this seems fine to me. > >> >> /be >> >> >> Till Schneidereit wrote: >> >>> >>> I'm beginning to like a conditional option on [[Invoke]]. >>> >>> Consider: [[Invoke]](P, ArgumentsList, Receiver, conditional=false) >>> >>> If conditional is false, it works just like the current [[Invoke]] >>> spec. >>> >>> If conditional is true and the [[Get]] value is not callable (this >>> includes undefined for a missing property) result is: [false, >>> [[Get]] result]. >>> if conditional is true and the [[Get]] value is callable, result >>> is [true, value returned from [[Call]] >>> >>> The conditional form would only be used in odd cases like the >>> toJSON call. >>> >>> ES code can accomplish the same thing via Reflect.invoke with true >>> as the 4th argument. >>> >>> I like it. This gets around the issue of distinguishing a return value >>> of `undefined` from "no callable property with that name found" and would >>> be easy to implement for proxies, too. >>> >> > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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