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[css-syntax] Comments on "Parser Algorithms" section

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 25 Jun 2013 16:12:52 -0700
To: www-style@w3.org
Message-ID: <20130625231252.GA16963@crum.dbaron.org>
Following are comments on section "5.4 Parser Algorithms" of
http://dev.w3.org/csswg/css-syntax/#parser-algorithms as of hg
revision 20a5abc61ca3.


I'm a little concerned about the "component value" terminology; I'd
prefer using a term that doesn't involve "value".  But I don't have
a better idea right now.


I think it would be clearer if, in "Consume a simple block", the
sentence:
  # Create a simple block with its associated token set to the current
  # input token.
said:
  # Create a simple block with its associated token set to the current
  # input token and its value set to the empty list.
to make it clear that there are two pieces in the data model of a
simple block.  (And, in general, it might be better to more clearly
define the data model of these objects by describing all the parts
of them when they're created, or perhaps even more explicitly.)


"Consume a qualified rule" is a bit unclear as to the type of the
value; I think think the opening sentence should probably replace
"nothing" with "empty list", since the value is a list.


I also find the spec lacks a bit of precision as to what consuming a
token actually means in terms of the current input token and the
next input token.  Many parts of the parsing spec say "consume the
next input token", which presumably makes it the current input token
unless there's been a previous "reconsume the current input token".
I think the spec should be more explicit about this, and also about
the fact that it would be an error for the spec to say "reconsume
the current input token" when it's already done so since the last
"consume the next input token".

I think there are also some cases where the wording gets things
wrong in terms of this model.  For example, I think the first
sentence of "Consume a declaration" which is currently:
  # Create a new declaration with its name set to the value of the
  # current input token. 
should have an additional "and consume the next input token" at the
end.  Then the following sentence which currently says:
  # Repeatedly consume 〈whitespace〉s until a non-〈whitespace〉 is
  # reached.
should instead say something like:
  # Until the current input token is non-<whitespace>, repeatedly
  # consume the next input token.
Without such a change, it makes the "Consume a declaration" prose
seem like it errors out every time since the initial identifier is
not a <colon>.


After doing this review, I'm comfortable with a first public working
draft of css-syntax.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Tuesday, 25 June 2013 23:13:18 UTC

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