[Harmony Proxies] Proposal: Property fixing

David Bruant david.bruant at labri.fr
Thu Jun 16 16:54:59 PDT 2011

Le 17/06/2011 01:23, Brendan Eich a écrit :
> On Jun 16, 2011, at 4:14 PM, Mark S. Miller wrote:
>> On Thu, Jun 16, 2011 at 4:05 PM, Brendan Eich <brendan at mozilla.com
>> <mailto:brendan at mozilla.com>> wrote:
>>     There is a second reason, mentioned recently: we are implementing
>>     the DOM on top of proxies, and the current WebIDL spec has
>>     non-configurable properties induced in its normative ES bindings
>>     from the IDL syntax. We want to match the spec.
>> Perhaps the WebIDL spec should be revised in exactly the same we
>> we're currently talking about revised arrays?
> It's in Last Call, so time is short. Also, implementations do matter,
> and non-configurable is valued by implementations that want to
> optimize by assuming the slot in the object won't go away. If we make
> Array length, NodeList length, etc. be configurable, we implementors
> will need some *other* hidden attribute.
I think that the deeper question we have to deal with now is the exact
semantics of configurability when it comes to "non-natural objects"
(array, host objects, proxies. Is there an official name for them in the
My understanding is that Allen seems to question the
applicability/application/ground of the spec on that ("Those restriction
had no teeth and it isn't clear that they have had any impact.").

Currently, ES5 - 8.6.2 says:
"The [[GetOwnProperty]] internal method of a host object must conform to
the following invariants for each property of the host object:
(...five bullets points...)"
I'd like to ask a few questions on this part of the spec:
Why are we expecting anything from host (all if including arrays?)
objects at all? (I know this one is naive and a bit provocative, but I
actually wonder)
Why are we expecting host (all if including arrays?) objects to respect
these particular invariants (this is actually 5 questions) and no other?

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