2012/12/18 Mark S. Miller <erig...@google.com> > I see no reason why this needs to be a reflected property. As to > whether it is an exotic internal property or just prose, that is a > specification expository issue for which I defer to Allen. But the > spec only needs such extra state for the exotic global object. There's > nothing general about it. >
The deeper issue pointed out by David here, I think, is that the triplet {enumerable,writable,configurable} does not cover the entire possible space of what one might want to express about the behavior of a property. If I understand correctly, the concrete case here is a property that cannot be deleted (which is normally expressed as configurable:false), but which should still remain configurable. I think it is unpractical and unwieldy to bake new attributes in to the ES spec for every use case that pops up. However, in the context of proxies, we have previously talked about the usefulness of allowing handlers to accept custom attributes in their defineProperty trap and return custom attributes from their getOwnPropertyDescriptor trap. By analogy, it might make sense for WebIDL-specified host objects to return additional custom attributes to describe the behavior of special properties that cannot be captured by {enumerable,configurable,writable}. The remaining "problem", of course, is that there is no standard semantics for custom attributes. As mentioned by Allen in another thread, the only solution here is for an exotic object to properly document its interface, including what meaning it ascribes to any custom attributes it wishes to report or accept. Cheers, Tom
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