2013/2/18 Andreas Rossberg <[email protected]> > On 16 February 2013 20:36, Allen Wirfs-Brock <[email protected]> > wrote: > > > It's to simplify the MOP and that simplification is directly reflected > as a simplification to the Proxy hander interface. Instead of 6 traps > (preventExtensions, isExtensible, freeze, isFrozen, seal, isSealed) only > two are needed. > > > > Also, having an explicit frozen object state simplifies some of the > object invariants which would otherwise perform explicitly specified > accesses to the target object which would be observable (if the target is > itself a proxy). > > Well, that is either a breaking change, such that implementations can > not actually be lazy about it, or it doesn't really remove complexity, > since you still need to infer the state as a fallback (i.e., it's just > an optimisation). > > I don't necessarily oppose making that breaking change, but we have to > be aware that, even though it's an optimisation, the change is yet > another complication of the object model. The additional state > modifies the meaning of per-property descriptors on a second level. > IIUC, defineProperty now has to check against that state, and > getOwnPropertyDescriptor somehow has to take it into account, too. For > direct proxies, the respective traps have to extend their validation > logic. Overall, not a simplification, as far as I can see. >
I've been thinking some more about get/setIntegrity and I've come to the same conclusion. While get/setIntegrity gets rid of 4 traps (sealed/isSealed/frozen/isFrozen), it does so at the expense of extra complexity in other parts of the MOP, in particular, adding yet more state to check and update in [[GetOwnProperty]] and [[DefineOwnProperty]]. Allen, in light of this, wouldn't you agree that it's better to keep the extra traps? Cheers, Tom
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