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[Bug 12072] Comments before <!DOCTYPE html> should be forbidden

From: <bugzilla@jessica.w3.org>
Date: Thu, 17 Feb 2011 19:01:34 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1Pq96c-0002u9-6U@jessica.w3.org>

--- Comment #18 from Daniel.S <crazy-daniel@gmx.de> 2011-02-17 19:01:33 UTC ---
(In reply to comment #14)
> * I'm familiar with "in the wild" about documents, but not about UAs…

An UA is in the wild if it has been released to the public.

> * It is core to HTML5's design to not trigger quirks mode.

Comments do not contradict this core. One implementeation does, unfortunately.

> * What do you mean by "feature" in this case? 
>   "<!---><!DOCTYPE html>" is not a feature!

Comments are a feature.

>      Feature: It is not "<!---><!DOCTYPE html>" in particular, but HTML
> comments in general, that has a buggy (read: proprietary) implementation in
> Internet Explorer. But HTML5 does still not forbid the comments feature ... !

I think that'd be the next step if we start to forbid comments in certain

>     But, in case of "<!---><!DOCTYPE html>" as well as "<!--[if
> ie]><![endif]--><!DOCTYPE html>", then IE's comments implementation has the
> unexpected and *undocumented* (undocumented by Microsoft) sideeffect [*] that
> it triggers quirks mode.

This bug is there, but it probably won't be there forever.

> [*] sideffect: It has been pointed out that comments are partly stylable in IE.

In quirks mode and standards mode up to IE7, but not IE8 nor IE9.

This issue is not related to comments only, but to other "invisible" elements
as well, e.g. noscript if scrits are enabled, input@type=hidden

Other browsers also have bugs in their quirks mode that are partially
undocumented. Besides, even if this case was forbidden, there'd still be an
issue in IE that had to be fixed.

>     That it can be avoided via "<!--[if !ie]><![endif]--><!DOCTYPE html>" as
> well as "<!--[if ie]><meta http-equiv="X-UA-Compatible"
> content="IE=Edge"><![endif]--><!DOCTYPE html>", only makes it even more
> confusing. But worse: it forces authors to use proprietary syntax in order to
> achive what HTML5 should be providing out of the box! And even worse: unless 
> it is made non-conforming, it is also impossible to catch these parsing mode
> affecting sideffects in conformance checkers.

Assume IE didn't have this bug. Would you still want to forbid Comments before
the doctype because the meta switch could be used there?

HTML5 provides no-quirks mode out of the box, IE doesn't yet.

Of course you're completely right when noting that an unwanted mode switch
could be detected if comments were forbidden before the doctype.

> It is not theoretical spec purity that favours forbidding comments before
> DOCTYPE. It is predictabilitiy for authors. That said: to forbid comments
> before the DOCTYPE, in many ways looks very natural: it means that conforming
> HTML gets a more "streamlined" look.

I'm afraid that there will be more and more cases where things like comments
may look "out of place" and get forbidden to ensure a streamlined look.

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Received on Thursday, 17 February 2011 19:01:35 UTC

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