Save Object.observe()! (please) + make WeakMap/WeakSet observable.

[Romuald Quantin]

> 2. For security purposes, only code that has been explicitly given access
to _both_ the weak map and a key may gain access to the value stored within
the > weakmap. This is why there is no enumeration—if there were, then any
code that could access the weak map could then also access all of the keys
and > > values. If that’s a desirable trait, then just use a Map.

What is the problem in accessing the keys with any code, which is the same
behaviour for any other object in javascript: String, Array, Object and so
on. The point is being able to do on a weak key so code can be processed
without being retained by the GC.

On 4 November 2015 at 22:36, Rick Waldron <waldron.rick at gmail.com> wrote:

>
>
> On Wed, Nov 4, 2015 at 8:16 AM Coroutines <coroutines at gmail.com> wrote:
>
>> On Wed, Nov 4, 2015 at 4:56 AM, Romuald Quantin <romu at soundstep.com>
>> wrote:
>>
>>> As an aside and as Coroutines,
>>>
>>> I never understood why there is this inability to enumerate WeakMap keys.
>>>
>>
>> If I had it my way there would be no WeakMap or WeakSet.  I'd have a
>> Symbol.mode similar to Lua's __mode meta(method/field?) that would show the
>> garbage collector that keys or values are weakly referenced in an object.
>> Or even:
>>
>> obj[Symbol.weakValues] = true;
>> obj[Symbol.weakProperties] = true;
>>
>> WeakMap isn't really all that special.  Set is important for how it
>> maintains only unique values are inserted - but you could do this with
>> Proxy.
>>
>
> This is all very misunderstood (both Romuald and Coroutines comments).
> WeakMap is extremely special, for these reasons:
>
> 1. The weakly mapped relationship between the key and value allows the
> runtime to gc the value once the key becomes otherwise unreachable.
> Specifically: if the _only_ reachable reference to the key is the weakmap
> relationship, then that relationship can be discarded and the value can be
> garbage collected at some implementation-determined time in the future.
> 2. For security purposes, only code that has been explicitly given access
> to _both_ the weakmap and a key may gain access to the value stored within
> the weakmap. This is why there is no enumeration—if there were, then any
> code that could access the weakmap could then also access all of the keys
> and values. If that's a desirable trait, then just use a Map.
>
> These things cannot be done with Proxy, because anything that Proxy does
> will inevitably be a strongly held reference.
>
>
> Rick
>



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