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Re: ECMA TC 39 / W3C HTML and WebApps WG coordination

From: Brendan Eich <brendan@mozilla.com>
Date: Thu, 24 Sep 2009 09:47:08 -0700
Cc: Sam Ruby <rubys@intertwingly.net>, public-webapps@w3.org, HTML WG <public-html@w3.org>, es-discuss <es-discuss@mozilla.org>
Message-Id: <04F26DF1-8C99-4338-8244-6EDF4A327084@mozilla.com>
To: Maciej Stachowiak <mjs@apple.com>
On Sep 24, 2009, at 7:55 AM, Maciej Stachowiak wrote:

> It seems like this is a Web IDL issue. I don't see any reason for  
> Web IDL to move to ECMA. It is a nominally language-independent  
> formalism that's being picked up by many W3C specs, and which  
> happens to have ECMAScript as one of the target languages. Much of  
> it is defined by Web compatibility constraints which would be  
> outside the core expertise of TC39.

Some of us on TC39 have lots of Web compatibility experience :-P.


> Probably the best thing to do is to provide detailed technical  
> review of Web IDL via the W3C process.

Expertise on both sides of the artificial standards body divide may  
very well be needed. The rest of this message convinces me it is needed.

One problem with inviting review via the W3C process is getting  
attention and following too many firehose-like mailing lists. es-discuss@mozilla.org 
  is at most a garden hose, which is an advantage.

Another problem is that not all Ecma TC39 members are W3C members  
(their employers are not members, that is).

There are transparency problems on both sides, IMHO. People in dark- 
glass houses...


>> https://mail.mozilla.org/pipermail/es5-discuss/2009-September/003312.html
>> and the rest of that thread
>>
>> https://mail.mozilla.org/pipermail/es5-discuss/2009-September/003343.html
>> (not the transactional behavior, which is out -- just the
>> interaction with Array's custom [[Put]]).
>>
>> https://mail.mozilla.org/pipermail/es-discuss/2009-May/009300.html
>>  on an "ArrayLike interface" with references to DOM docs at the  
>> bottom
>>
>> https://mail.mozilla.org/pipermail/es5-discuss/2009-June/002865.html
>>  about a WebIDL float terminal value issue.
>
> It seems like these are largely Web IDL issues (to the extent I can  
> identify issues in the threads at all).

TC39 members, Mark Miller articulated this yesterday, hope to restrict  
host objects in future versions of the JavaScript standard from doing  
any nutty thing they like, possibly by collaborating with WebIDL  
standardizers so that instead of "anything goes" for host objects, we  
have "only what WebIDL can express".

Catch-all magic where host object interfaces handle arbitrary property  
gets and puts are currently not implementable in ES -- this may be  
possible in a future edition, but even then it will carry performance  
penalties and introduce analysis hazards. We hope to steer ES bindings  
for WebIDL-expressed interfaces away from catch-all patterns.

Beyond this tarpit, we're interested in the best way to linearize  
multiply-inherited WebIDL interfaces onto prototype chains, or whether  
to use prototype chains at all -- or in the seemingly unlikely event  
ES grows first-class method-suite mixins, binding WebIDL inheritance  
to those. We would welcome use-cases and collobaration, at least I  
would. Who knows what better system might result?


>> There are larger (and less precise concerns at this time) about  
>> execution scope (e.g., presumptions of locking behavior,  
>> particularly by HTML5 features such as local storage).  The two  
>> groups need to work together to convert these concerns into  
>> actionable suggestions for improvement.
>
> There was extensive recent email discussion of local storage locking  
> on the <whatwg@whatwg.org> mailing list. We could continue here if  
> it would be helpful. I'm not sure it's useful to discuss in person  
> without being up to speed on the email discussion. Here are some  
> relevant threads: <http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-September/022542.html 
> > <http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-September/022672.html 
> > <http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-September/022993.html 
> > <http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-September/022810.html 
> >.

Thanks for the links, I was aware of these but hadn't read them.

Mandatory try-locks in JS, just say no.


> I'm not sure what the other concerns about "execution scope" are -  
> seems hard to discuss fruitfully without more detail.

The term I used was "execution model". "scope" is a mis-transcription.


>> We should take steps to address the following "willful violation":
>>
>> If the script's global object is a Window object, then in JavaScript,
>> the this keyword in the global scope must return the Window object's
>> WindowProxy object.
>>
>> This is a willful violation of the JavaScript specification current  
>> at
>> the time of writing (ECMAScript edition 3). The JavaScript
>> specification requires that the this keyword in the global scope
>> return the global object, but this is not compatible with the  
>> security
>> design prevalent in implementations as specified herein. [ECMA262]
>
> Wasn't ES5 fixed to address this?

No, nothing was changed in ES5 and it is not clear without more  
discussion with various experts active in whatwg, w3, and Ecma what to  
do.

Since you asked, I think you make the case that we should collaborate  
a bit more closely.


> I know the feedback was passed along.

Yes, but describing the problem does not give the solution.

/be
Received on Thursday, 24 September 2009 22:18:12 GMT

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