Last modified: 2013-07-12 19:43:20 UTC
According to Special:ExpandTemplates, if you use a page title that has "ISBN" embedded in it, such as "Pages with ISBN errors" then {{FULLPAGENAME}} has unexpected behavior. Specifically there is a html-entity   following the word ISBN rather than a space. Obviously space and encoding character #32 are the same thing visually, but they are not the same thing from the point of view of comparison operations such as #ifeq. This can lead to unexpected behavior. Please fix it to remove the unnecessary encoding.
(In reply to comment #0) > According to Special:ExpandTemplates Any link? Any accessible testcase somewhere to see the behavior? Which MediaWiki version is this about?
Current Mediawiki. Here is a demonstration page: http://test2.wikipedia.org/wiki/This_is_an_ISBN_pagename_test
If I had to guess, I think the place to look for this is actually in Mediawiki and not one of the extensions. Specifically, I'd suggest starting at: Parser::doMagicLinks Which does the ISBN transform described at: http://www.mediawiki.org/wiki/Manual:Parser.php (Item #9)
FULLPAGENAME and other variables goes through wfEscapeWikiText, which does this to avoid parsing as magic links
