On Feb 10, 2012, at 3:46 AM, Tom Van Cutsem wrote:
> Hi,
>
> I'm also in favor of exposing __proto__ as an accessor on the grounds that it
> is least magical. I'm worried that the changes made here to the core internal
> methods [[Get]], [[Put]], [[DefineOwnProperty]] and [[Delete]] will give
> proxies a hard time to properly emulate this behavior if they would want to
> do that. How would a proxy handler be able to access the internal variable
> UnderscoreProtoEnabled?
function UnderScopeProtoEnabled() {
var p={};
return Object.getPrototypeOf({__proto__:p})===p;
}
I believe the root question is whether we are willing to expose for arbitrary
usage a function that is able to modify the [[Prototype]] of any object. EG:
Object.setPrototypeOf = function (obj,proto)
{Object.getOwnPropertyDescriptor(Object.getPrototypeOf({}),"__proto__").set.call(obj,proto)};
Once we have don this, that function can be used in arbitrary places, including
as or within get and set functions of any accessor property with any name on
any object.
>
> (I currently assume that in any event, aProxy.__proto__ would just trigger
> the "get" trap for "__proto__" and that all of this magical behavior does not
> apply to proxies, only built-in normal objects.)
Presumably.
>
> Also +1 to Gavin's proposed alternative to the frame-check.
Yes, Gavin check amounts to the same thing as mine, once you allow for
differences in how we define Object.prototype.__proto
The important ifference is whether that check is make in the internals of a
function that is visible as an accessor get function or whether the check is
hidden inside the implementation of the standard internal methods.
Allen
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