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Re: [Syntax Level 3]

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 28 Aug 2012 14:42:59 -0700
Message-ID: <CAAWBYDAcBD+zYUsVCoQBcQtOfqBAuKAzFGcLS+u=wStUobFADg@mail.gmail.com>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: Brian Kardell <bkardell@gmail.com>, fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>
On Tue, Aug 28, 2012 at 2:36 PM, L. David Baron <dbaron@dbaron.org> wrote:
> On Tuesday 2012-08-28 13:38 -0700, Tab Atkins Jr. wrote:
>> On Tue, Aug 28, 2012 at 1:21 PM, L. David Baron <dbaron@dbaron.org> wrote:
>> > On Tuesday 2012-08-28 12:37 -0700, Tab Atkins Jr. wrote:
>> >> The point is that, as currently implemented, whenever I see a ! in a
>> >> rule, I need to push it into a substack, along with all subsequent
>> >> whitespace and comment tokens, until I see a token that's neither
>> >> whitespace nor a comment.  If it's an IDENT(important), I throw away
>> >> the stack and make the declaration important.  If it's anything else,
>> >> I insert the entire stack into the declaration's value.
>> >>
>> >> This isn't hard.  It is, however, inelegant and *useless*.  There is
>> >> absolutely no reason to allow this, and it would simplify parsers the
>> >> spec and parsers to disallow it.  There shouldn't be any compat impact
>> >> to the change.
>> >
>> > Why should we allow ! within values?  It seems already somewhat
>> > established as a delimiter.  Can't it just always end the value at
>> > the !, and then make the thing after it make the declaration invalid
>> > if it's something other than IDENT(important)?
>>
>> I'm amused that your alternative to my syntax change is a larger
>> syntax change. ^_^
>
> It's not really a change, though.  It's merely a removal of a
> reservation of syntax.
>
> In other words, one way to look at the forward compatible grammar
> is that it reserves large amounts of syntax for potential future
> use.  What I'm proposing unreserves a tiny piece of it.  It doesn't
> change the error handling behavior at all.
>
> Also, I'm not proposing that we change the forward-compatible syntax
> to treat things with multiple !s in a declaration or with things
> other than important after the ! any differently from any other
> invalid declaration.
>
> I'm just proposing we don't allow ! inside the value of a variable
> (which I think I'd proposed before), or inside the values of future
> properties.

I'm not particular against this change.  It keeps the spec simple too,
and I doubt it'll have much effect, so it's fine.

Question, though.  ! is still allowed inside of functions, just not at
the top level of a declaration.  Are variables affected here?  That
is, does a variable still do the basic parsing of "oh look, a function
of some type", or does it preserve the value as a pure token stream?
If the latter, do we need an exception here somehow?  (If the latter,
I don't think it's acceptable to say "too bad, no ! in variables",
because we may very well have functions that allow !s as parts of
their grammar (perhaps as part of a selector), and we should be able
to store these functions in a variable.)

~TJ
Received on Tuesday, 28 August 2012 21:43:47 GMT

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