Hi,
I feel like I've been in an equivalent discussion some time ago, so
taking the liberty to answer.
Le 02/12/2014 13:59, Andreas Rossberg a écrit :
On 1 December 2014 at 03:12, Mark S. Miller <erig...@google.com> wrote:
On Sun, Nov 30, 2014 at 12:21 PM, Boris Zbarsky <bzbar...@mit.edu> wrote:
Per spec ES6, it seems to me like attempting to define a non-configurable
property on a WindowProxy should throw and getting a property descriptor for
a non-configurable property that got defined on the Window (e.g. via "var")
should report it as configurable.
Can you clarify? Do you mean that it should report properties as
configurable, but still reject attempts to actually reconfigure them?
Yes. This is doable with proxies (which the WindowProxy object needs to
be anyway).
* the defineProperty trap throws when it sees configurable:false
* the getOwnPropertyDescriptor trap always reports configurable:true
* and the target has all properties actually configurable (but it's
almost irrelevant to the discussion)
Also, how would you allow 'var' to even define non-configurable
properties? If you want DefineProperty to throw on any such attempt,
then 'var' semantics would somehow have to bypass the MOP.
Thinking in terms of proxies, the runtime can have access to the target
and the handler while userland scripts only have access to the proxy
(which the HTML Living standard mandates anyway with the difference
between Window and WindowProxy objects. No userland script ever have
access to the Window object).
The handler can have access to the list all declared variable to know
which property should behave as if non-configurable.
David
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