David Bruant wrote:
Le 15/12/2012 19:11, Brendan Eich a écrit :
David Bruant wrote:
If I create a non-configurable property with a getter that I define
(such
as `() => 3`), I know that accessing the property will always produce
a known value. Relaxing this restriction means that proxies could
produce whatever they wanted in this situation.
Indeed. Note that it's true currently true with ES5 host objects.
The frozen getter/setter could be a working solution as well.
Frozen accessors would be best if we can get away with the
incompatibility.
I've given more thought. Frozen accessors can't be a solution. Only
deeply frozen would be.
Oh sure -- that goes without saying (or so I thought when I wrote it :-P).
If the accessor isn't deeply frozen, then, it means that any
non-frozen object that can be reached through the accessor can be used
as a communication channel between 2 browsing contexts that were in
the same iframe.
Among other things, "deeply frozen" means to freeze the accessor's
[[Prototype]] which is Function.prototype which is probably not workable.
Yes, so to avoid the "Ice-9" problem, these would have to bottom out in
a "null realm" where everything is frozen: Function.prototype,
Object.prototype, anything else required (is anything else required for
function objects to be deeply frozen?).
Or there are probably other things like comparing iframes
contentWindow.Function.prototype objects over time (when changing src)
that wouldn't be compatible.
If you buy the "null realm" idea, the only breaking change would be if
someone could extract the get or set function via
__lookupGetter__/__lookupSetter__ or the ES5 standard forms, inspect
them and find the current window's realm built-ins. Or monkey-patch the
current realm's built-in Function.prototype or Object.prototype and
expect those properties to be inherited by the get and set functions.
But this seems like something we could get away with breaking, maybe.
Back to the idea of reflecting different getter/setters for
non-configurable accessors, I guess.
Let's talk about deep-freezing and the null realm more.
/be
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