Hi, I've recently filed a spec bug [1] and given more thoughts about it that goes beyond the suggested restructuring so I'm bringing it up here. This posts ends up with an unresolved issue, but I hope a solution can be found.
Let's talk about property descriptors. Currently, in the spec, property descriptors have their own type (with "fields" and accessing things in these fields). It's a type that matches very well with objects, so the mapping with Object.defineProperty input and Object.getOwnPropertyDescriptor is rather obvious. However, when we think about proxy traps, the proxy traps can't have access to an abstract data structure, so the proxy spec uses regular objects for trap communication. My bug was about making the use of objects official in the spec internals... until I realized that ES6 has maps. I'm writing to propose a change which is to make property descriptor ES6 maps both inside the traps and to the external interface. There is no problem for traps (except maybe that it changes the current Firefox implementation...). A backward compatibility may exist for ES5 code: * Object.defineProperty using maps => For legacy reason, it would keep accepting plain old objects, but when passed a map, it would use the map get/set/has protocol. * Object.getOwnPropertyDescriptor returning maps => That part is a bit trickier, because current code has a ridiculous amount of 'desc.configurable', 'desc.enumerable', etc. in it and this must keep working. I'm not sure I have found an acceptable idea for this part. One major issue I see is the naming conflict between Map.prototype.get/set and the 'get' and 'set' attributes of property descriptors. In the hope it will inspire someone who'll be able to find a solution. David [1] https://bugs.ecmascript.org/show_bug.cgi?id=863 [2] http://wiki.ecmascript.org/doku.php?id=harmony:proxies_spec _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
