Allen, Mark and I discussed the [[Origin]] issue and came to the following consensus:
We remove [[Origin]] and revert to the originally specified behavior (< http://wiki.ecmascript.org/doku.php?id=harmony:proxies_spec>) where the descriptor returned by the proxy is coerced into a fresh, normalized, completed, ordinary descriptor object. This ensures complete backward-compatibility with the ES5 behavior (i.e. Object.getOwnPropertyDescriptor will always return a fresh, complete data or accessor descriptor), and doesn't allow a proxy to play tricks with descriptor objects. Allen's remaining concern is that this disallows proxies (or new exotic objects) from inventing new types of descriptors, next to data and accessor descriptors. Due to backwards-compat. constraints, we're basically stuck with these two types of property descriptors forever. The originally specified Proxy behavior also included copying any non-standard attributes provided by the proxy onto the fresh descriptor object. However, if we're serious about keeping Object.getOwnPropertyDescriptor backwards-compatible with existing ES5 code, we may be better off by not augmenting descriptor objects with non-standard attributes, even if this is unlikely to break existing code. As Jason mentioned, if proxies want to introduce new per-property attributes, they can provide other means of getting at that meta-data rather than abusing the standard reflection API. So, the current proposal is to spec [[GetOwnProperty]] for Proxies such that the descriptor returned by the trap is coerced into a fresh, normalized, complete descriptor object, without copying custom attributes. Relevant bug seems to already have been filed by Andre: < https://bugs.ecmascript.org/show_bug.cgi?id=2382> Cheers, Tom
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