Re: [whatwg] with omitted tags

Fri, 26 Dec 2008 09:03:05 -0800 

Philip Taylor ha scritto:

I can start with a simple document that's probably conforming and that
the validator doesn't complain about:

  <!DOCTYPE html><html><head><title></title></head><body></body></html>

Then I can read the "Writing HTML document: Optional tags" section, which says:

  "A head element's end tag may be omitted if the head element is not
immediately followed by a space character or a comment.

  A body element's start tag may be omitted if the first thing inside
the body element is not a space character or a comment, except if the
first thing inside the body element is a script or style element.

  A body element's end tag may be omitted if the body element is not
immediately followed by a comment."

So I choose to omit the </head><body></body> because I think those
rules say I can do so. I get:

  <!DOCTYPE html><html><head><title></title></html>

But now I get a parse error, which I think is because the </html>
comes in the "in head" insertion mode and is "Any other end tag: Parse
error. Ignore the token.", so something seems wrong.
AIUI, omitting those closing tags is a parse error anyway, but in certain situations the parser can fix the code automatically because the state to enter/remain in is unambigous. Thus a validator notifies a parse error, while a browser keeps the error internally and handles it when possible. 

AIUI, a brower would notice the error but might ignore it since both in

<!DOCTYPE html><html><head><title></title></html>

and in

<!DOCTYPE html><html><head><title></title></head><body></body></html>
there is nothing to show but the background color of the <html> root element as provided by default style sheets (that is, they're equivalent), whereas finding a "showable" start tag (like a <p>) would lead (about) to automatic insertions of </head> and <body> and to reconsume the tag as "in body" insertion mode. 

Indeed, section 8.1 says,
/'This section only applies to documents, authoring tools, and markup generators. In particular, it does not apply to conformance checkers; conformance checkers must use the requirements given in the next section ("parsing HTML documents").' 

///thus section "8.1.2.4 Optional tags" does not apply to validators. ;-)
[ space characters and comments may be handled correctly anyway, but omitting the </head> tag would result in a different document tree, thus athors and authoring tools should take care that 

<!DOCTYPE html><html><head><title></title><!-- this is a comment --></html>

and

<!DOCTYPE html><html><head><title></title></head><!-- this is a comment 
--></html>

are not fully equivalent ]


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