thomas.dalton wrote:

I think the parser is getting confused when it sees the end of a wikilink without being able to find the start of it, and it never realises that it is in a template parameter, so ends up not parsing anything at all and just outputs the wikitext. It's possible the parser could be altered to work better in this situation, but I doubt it would be easy. I think your best bet is to alter the template (perhaps add an alternative parameter which doesn't have [[ and ]] added to it).

ssanbeg wrote:

The problem is that once the parser starts parsing the [[, then the | is used for that. The solution is to delay parsing the link until after the template is parsed. I've already fixed the example page listed; this behavior is inherent in the syntax, so changing the parser wouldn't help.

mr.heat wrote:

This is not a parser bug. Simple change the template:

{{#ifexist: {{{Art}}} | [[{{{Art}}}]] | {{{Art}}} }}

Then almost all kinds of parameter text can be used:

Art = Link1
Art = [[Link1]]
Art = [[Link1]], [[Link2]]

thomas.dalton wrote:

That's not perfect - really you want an #isAValidPageName rather than #ifexist, otherwise you won't get redlinks for pages that could exist but don't.