David Bruant wrote:
2012/10/10 Brendan Eich <[email protected] <mailto:[email protected]>>
Tom Van Cutsem wrote:
We should also be wary of adding even more Proxy constructors,
as we'll otherwise end up with a combinatorial explosion
(revocable branded proxies, branded proxies with a symbol
whitelist, etc.)
But didn't David find a way to avoid Proxy.revocable, namely make
revocation swap in an all-throwing-traps handler?
Unfortunately no. I agree with Tom concern of combinatorial explosion,
because we will have revocable, branded, and what's next?
However, the symbol whitelist isn't part of it. The whitelist doesn't
make a new type of proxies.
Yes, I agree with all that (except the revocable constructor, see
below), including general apprehension of combinatorial explosion.
Just trying to keep up here (and hoping we indeed avoided a
revocable proxy constructor).
Even with the idea of native support for membrane as I presented it,
it doesn't change that anyone holding a reference to a proxy
indirectly keeps a reference to the target, thus causing the GC to not
be able to collect the target.
Why would not the target be nulled and the handler be replaced with a
handler full of throwing traps? Sorry if I missed a message on this.
We need platform support for revocation, because it cannot be
implemented by JS code.
I quite agree, but this does not mean a Proxy.revocable constructor,
unless you want a revoke method to work only on proxies distinguished by
being created via an alternative constructor.
IIRC (and I hope I do!) we were considering RevokableProxy or
Proxy.revocable only because non-revocable proxies cannot tolerate
overhead in dispatching their traps to check for a default-false revoked
internal property. But your idea of nulling target and replacing handler
with a throwing handler seemed to avoid any overhead.
So is the issue the revoke API and a desire to "narrow" it to apply only
to proxies distinguished from birth as revocable? If so, why?
/be
All in all, membranes can be implemented today. I find the idea of
using dummy targets a bit awkward, but it works. If after some
experience using proxies, the cost turns out to be prohibited, There
is still room for improving proxies with what proposed or whatever
else in a later version of the spec I think. The issue I'm pointing is
not as urgent as the revocation issue was.
David
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