As MichaelSamuels helpfully pointed out on TWikiIRC, TWiki is inserting <p /> tags into the table. I believe this is not legal XHTML.

-- CrawfordCurrie - 17 Mar 2004

Yes, this is fairly horrible, but at the same time I'm not sure how to solve it. TWiki arbitrarily mixes two languages, HTML and TWikiML, without a clear definition of whether any given syntactic element is in TWikiML or HTML (except that TWikiML gets processed first). I tried to fix the TWiki paragraph formatting code a while back so that it would not emit unneeded <p> tags, but it's a lot harder than it looks at first - for example, if a 'paragraph' preceded by a blank line starts with HTML markup, should a <p> tag be emitted (because it's a new para) or suppressed (because we are really in a 'full HTML' part of the page). There's some code at MozillaNotStylingXHTML but it's broken for important cases at present.

Maybe TWiki should do some basic HTML tag parsing (just matching beginning and ending tags, not real parsing) to work out whether it's in an 'HTML area' or not? Or maybe there should be a special TWikiML tag, e.g. <usehtml> tag pair, that says 'here be HTML, don't touch it'? You could then put it around tables that have embedded newlines.

-- RichardDonkin - 17 Mar 2004

Fixing this is not trivial as Richard pointed out, it also could reduce the performance.

Strictly speaking this is a bug. However, since we encourage users to use TWikiML instead of HTML, one could argue that people who use HTML (e.g. to create TWikiApplication) should be aware not to use empty lines between HTML tags where it is not allowed to use paragraphs.

Is there any need for empty lines between HTML tags?

TWiki does allow HTML but with some limitations. For example, a tag cannot span more then one line. On the same line, the empty line limitation could be a documentation question, not a bug fix.

-- PeterThoeny - 18 Mar 2004

The only reason I noticed it is because the tableprepend template to the CommentPlugin was leaving blank lines in the middle of tables. It's a difficult decision when faced with a choice between allowing TWikiML between HTML tags and disallowing it. But it's also a shame that TWiki can't claim XHTML1.0 compliance. On balance a documentation fix would be fine. Note that while XHTML1.0 compliance isn't claimed in the documentation (AFAICT), it is certainly implied in TWikiSystemRequirements

-- CrawfordCurrie - 18 Mar 2004

This is now documented in TextFormattingRules

-- PeterThoeny - 11 Jul 2004