ES4 News and Opinion

ES4 News

Some news on language size: the proposed ECMAScript 4th edition (ES4) grammar is a bit more than twice as big as ES3’s, counting several ways (concrete productions, abstract syntax tree node types):

Syntax                   ES3   ES4
------                   ---   ---
Concrete                 238   490
Type Exprs                    50
Classes & Interfaces          23
Patterns                      17
Abstract                  33    77

This is not out of line given the eight years since ES3, which came less than three years after ES1. Much of ES4 has been developed and shipped in ES3-based languages: AS3 in Flash, JS1.6 and 1.7 in Firefox, Opera’s extensions including array destructuring. And we’re being generous with syntactic conveniences, which desugar to a smaller core language. On the compatibility front, we have a new document on known incompatibilities between ES3 (ECMA-262 Edition 3 the spec, not real-world behavior of ES3 implementations in browsers — note well) and ES4.


Chris Wilson: “… I don’t think the other Microsoft guys ever intended to say ‘everything about ES4 is bad’.” Pratap Lakshman (Microsoft): “We do not support or agree to the current ES4 proposal, either in whole or in part.” Individual intentions can be hard to judge, and anyway matter less than effects. My point is not to guess about intentions, only to point to statements and actions.


It’s a relief to learn that Chris’s charge of “shouting down dissent” — confusingly juxtaposed with his words “I think it’s a shame that dissenting opinion has been hidden from view”, which seem to point to the ECMAScript standards body’s majority in a way that left many readers thinking that someone in Ecma TC39-TG1 actually shouted at Microsoft reps during a meeting — was really just a complaint about bloggers “shouting” (which is news-at-11 fodder, don’t you think? I’ve seen shouting from all sides on this one).

That leaves the charge of “ignoring”, which was not aimed at the blogosphere — that accusation was aimed straight at “the TG-1 committee chair”, presumably me (I’m TG1 Convenor). But it is simply false to claim I’ve ignored compatibility concerns or anything else raised by a member of TG1.
Still, if we can make progress by agreeing that bloggers sometimes shout, or show bad manners, I’m all for it. My manners aren’t perfect, and I’m sorry when they fail. But morals trump manners, and the overarching issue before us remains: is it right for ES4 to be stalled in committee, or for ES3 to be forked into a now-hidden “ES3.1”, because Microsoft and Doug Crockford object to ES4 on general grounds?


Whatever you think of ES4 (and it’s not done yet — we just released a reference implementation update), the history nicely reconstructed by Neil Mix should make clear that it has been a long time coming, most of the time without anyone refusing to support it “in whole or in part”. The July 2006 meeting notes include a statement from Pratap that ES4 would be implemented in the next major IE release after IE7.

Of course this all changed, starting early in 2007, officially only in March. But why did it change? Was all the pre-history, including Microsoft’s implementation of JScript.NET, a big mistake? Did JScript.NET really “fail”, and fail in any way that bears on ES4 itself or its future on the client side of the web? I think not, and the generalities about breaking the web, or the web not needing to change much, do not explain this about-face from 2006 to 2007.

Anyone who reads the face-to-face meeting notes can see that everyone working on ES4, including me, would work on topics of interest with whomever attended meetings. And we worked together well enough when focused on technical issues. Allen Wirfs-Brock of Microsoft, in particular, is very knowledgeable and insightful.


But the cold hard fact, documented in that September face-to-face meeting note, is that the dissenting minority in TG1 rejects ES4 in whole and in part. There does not seem to be room for compromise.
As TG1 Convenor, I’ve tried to keep any “3.1” work in the context of ES4, to avoid a fork of ES3 into incompatible derivative languages. In particular, any ES3.1 should be a subset of the ES4 reference implementation, so it can be tested. This seemed agreeable in March, and Allen reiterated agreement in April.
Since April, it has been impossible for the majority of TG1 to evaluate ES3.1. There has been no work on the wiki, and almost no communication to the majority of TG1 about what’s in ES3.1 or how it will be tested for backward compatibilty with ES3 and forward compatibility with ES4.

Do The Right Thing

Neither a hidden and unready alternative proposal, nor general objections from a minority in the group, should halt a standard in progress. ES4 should be delayed or abandoned only on technical demerits, demonstrated specifically. There are enough implementors working together to make a standard, and ES4 as it has evolved has always been the expected successor standard. To block it based on general fears and opinions prejudges both the final standard and the market for it. The market, not Ecma TC39-TG1, should decide ES4’s fate.

It should be clear by now that the majority of TG1, who favor ES4, want to keep the group from splitting, or otherwise risking incompatible forks of ES3. Everyone loses in that scenario. We wouldn’t have spent all the time in the wiki and at meetings if we all, including me, didn’t want a win-win outcome for all players. And I personally suggested to Chris in March that Microsoft could be a big winner by backing ES4 and supporting it in IE.

Is it still possible for everyone to win? I have to say I’m not as positive as I used to be. If we all work on testable compatibility via the reference implementation, then I’m somewhat more hopeful. But it will take a better stance than rejection of ES4 “in whole [and] in part” to get somewhere.

Recap and Prelude


Too much travel and conference fun, too little blogging:

I was invited to present a keynote at ACM ICFP 2005 in Tallinn, Estonia at the end of September. The very kind program comittee was unanimously interested in me as the ‘where the rubber meets the road’ speaker. I hope I delivered; I still have tire marks on my back from the Netscape 2 days.

It was an honor to speak and attend, and I made some good connections and introductions. Among these was Autrijus Tang, who is a hero in my book for promoting both Perl 6 and Haskell in one fell swoop. Functional programming is on the rise, and I’m glad that JS is playing a small (but very widely distributed) part.

While there, the Skype guys were nice enough to have me out to dinner — I hope to reciprocate when they’re in the bay area.

The old town in Tallinn is delightful, full of charming architecture from various eras going back to the high Middle Ages. I’m planning my move already (half-kidding).

After that came Web 2.0, which was a blur of VCs, old friends, and new companies. Everyone noticed the bubbly atmosphere. Mitchell was in fine form in a kind of interleaved interview titled Can Open Source Stay Open?


I have been working more and more with ECMA TG1 on JavaScript standards, at first E4X (which was all but done when Mozilla joined ECMA last year) and now Edition 4. Our goals include:

  • Bringing Edition 4 back toward the current language, so that prototype based delegation is not a vestigial compatibility mode, but the dynamic part of an object system that includes classes with fixed members that cannot be overridden or shadowed.
  • Allowing implementors to bootstrap the language, expressing all the meta-object protocol magic used by the “native” objects (ECMA-262 Edition 3 section 15), including get/set/call/construct and control over property attributes such as enumerability.
  • Adding type annotations without breaking interoperation of existing and new editions, in support of programming in the large — which is needed more and more in XUL and modern web applications.
  • Fixing longstanding problems that bite almost every JS hacker, as I’ve discussed previously.

Our intention is to finish by the end of next year, and to implement and test interoperation along the way as much as possible. The Macromedia folks are quite far along in their implementation of a derivative of Waldemar’s Edition 4 draft, called ActionScript 3.

At the same time, and while also slaving over a hot Gecko 1.8 / Firefox 1.5 stove, I have been working with Mozilla leaders, especially shaver and other drivers, on roadmap-level plans for the next year to 15 months.

These plans build on bottom-up planning from module-sized projects such as the move to Cairo graphics as Gecko’s new graphics substrate, the Python for XUL project, and the XULRunner project. We aim to balance the need to ship Firefox releases that innovate quickly in user-facing ways with the longer cycle time required to uplift the web platform with better graphics features and content languages in Gecko 1.9.

The fruits of all this planning, in the form of a coherent draft overview containing links to project and wiki pages, and a schedule and branching plan for everyone to review, will be pushed out to imminently. The old roadmap page will contain at least links, if it doesn’t beome a redirect. Stay tuned.