Nathan Wall wrote:
Brendan Eich wrote:
Nathan Wall wrote:
In the case of (2), the implementation using a private symbol will fail on a
call to `setTime` when the object is frozen (I think).
Nope, we agreed that frozen objects support setting pre-existing (added
before the object was made non-extensible) properties named by private
symbols.
I wasn't aware, but that significantly improves the case for symbols. I'm glad
to hear it! However, it also begs the question of why symbols should behave
differently from WeakMaps/closures in the presence of Proxies (via
unknownPrivateSymbol trap).
WeakMaps transpose the terms of property access:
obj[sym] <=> wm[obj]
This seems important! Do you propose, if obj is a proxy, to trap with wm
as key for the latter?
David Bruant wrote:
In the case of (1), the implementation using a private symbol will have
internal accesses to the `timestamp` symbol exposed through the
unknownPrivateSymbol trap.
The trap does not expose the symbol. That would be a bad leak.
The third "whitelist" argument in the proxy constructor is here to
communicate whether the proxy knows the privatesymbol or not.
When [[Get]] or [[Set]] (or other property operations) happens with a
whitelisted private symbol, the get or set (or other) trap is called
with the symbol itself (since it's known). If the name isn't in the
whitelist, the unknownPrivateSymbol trap is called with target as the
*only* trap argument (the private name is not exposed and that's on
purpose!)
I'm sorry, I was unclear. I understand that the symbol itself is not exposed,
but the fact that some symbol was accessed is.
No, not if the symbol is not in the whitelist. Zero information leak is
required.
/be
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