On Tue, 18 Aug 2015 05:15:05 +0200, MZMcBride z@mzmcbride.com wrote:
The only cited example of real breakage so far has been mismatched
<div>s. How often are you or anyone else adding <div>s to pages? In my experience, most users rely on MediaWiki templates for any kind of complex markup.
Echoing my initial reply in this thread, I still don't really understand what behaviors from Tidy we want to keep. I've been following https://phabricator.wikimedia.org/T89331 a bit and it also hasn't helped answer this question.
Mismatched any tags. A an opening <foo> or closing </foo> tag without a pair can wreak havoc on the entire page, including the interface.
I recall reports of unclosed <small> or <b> reducing the font size of or bolding the entire page. I can't find that one, but here's a small collection of bugs caused by Tidy unintentionally not running in various contexts: T27888 T29889 T40273 T44016 T60042 T60439.
You could easily engineer this to hide the tabs if you were malicious (making it impossible for casual users to edit the page, say, to fix the broken markup), and it might even be doable by accident.
We really do need this feature. Not anything else that Tidy does, most of its behavior is actually damaging, but we need to match the open and close tags to prevent the interface from getting jumbled.