Well stated, respect.
I think you are underweighting the utility of private symbols. The
counter-argument I want to make is: what if high-integrity privacy (via
weakmaps as you propose) as a popular practice would take off, but with
weakmaps there's no optimization (PICs, TI) as there is for property
access in top engines today, so developers avoid privacy via weakmaps.
They might use unique symbols. Those paths probably optimize for free as
with string-keyed properties. But what if they just keep on truckin'
with public string-keyed properties?
This is a weak argument, I admit. It may be that adoption of any kind of
privacy, weak or strong, is going to be slow and soft, especially
without syntax (a la TypeScript, which has no-integrity privacy!).
Not throwing in the towel, just wanted to respond with the best
counter-argument I can make.
/be
Kevin Smith wrote:
Thank you Mark, for the GC hint proposal: it matches what was my
(admittedly naive) intuition. And thanks, Allen, for the thorough
description of GC issues. Very helpful!
Some points, in no particular order:
- It seems likely to me that the implementation complexity of {private
symbols, weakmaps} will be on par with the implementation complexity
of {weakmaps with hints}.
- Reflectivity of all property names is a useful feature that should
not be discarded lightly.
- Simplicity in the object model is an advantage for everyone
attempting to reason about objects.
- Having one kind of symbol is easier to conceptualize than two.
Indeed, private symbols could be an attractive nuisance if they lead
developers toward over-securing their abstractions.
- Unique symbols provide sufficient encapsulation for
software-engineering purposes.
- It is my conjecture that high-integrity privacy will be required by
a small fraction of projects (such as SES sandboxing engines), and the
developer audience for these features will be "power-users". In this
case, private symbols might be an over-optimization of a corner case
(although it's an important corner!).
- It looks to me like much of the work to make ES6 future compatible
with private symbols has already been done.
- During the ES7 design process, there will be plenty of user
experience with weakmaps and proxies to draw from. This should make
the private symbol decision much clearer.
{ Kevin }
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