Last modified: 2011-03-13 18:06:07 UTC
When page has an attribute defined in the way that it's output is completely suppressed, e.g.
[[Date of birth:=1976-03-31|]]
page breaks and when edited again, shows
[[Date of birth:=1976-03-31|=1976-03-31]]
instead, replacing empty title with '=' sign followed by attribute value.
Workaround is to put space after | symbol like this:
[[Date of birth:=1976-03-31| ]]
This is a feature, not a bug, more information at http://en.wikipedia.org/wiki/Help:Pipe_trick.
Apparently it's a bug in Semantic MediaWiki Extension, result appears as "=1976-03-31" and makes absolutely no sense.
Also it doesn't get formatted as date (according to user preferences) while [[1976-03-31]] does. This might be related to bug 9620.
Re-assign to extension developer for triage/comments.
Sorry, Sergey, I am afraid I cannot fix this. SMW now prefers to use two colons, ::, instead of :=. So if you want the pipe trick to produce better output, then MediaWiki should seek the last colon instead of the first (but that would cause other problems, I guess, or at least change the current behaviour). This is not a thing that SMW can change, at least not without major additional efforts (such as pre-encoding the colons in some other way with some other parser hook).
So, yes, this is a bit annoying, but we will not change it. SMW might soon support other means for adding hidden annotations, and generally support non-link input syntax (the link syntax here is apparently the core of our problem). Also, the workaround with a space as mentioned in earlier comments works pretty well.
OK, no problem. For a year since this bug was discovered, I got used to use [[Property::Value| ]] to suppress the output or [[Property::Value|Value]] manually instead of using a pipe trick.
It might be worth adding this to SMW documentation somewhere around the description of '::' syntax that it breaks "pipe trick" so others don't get confused over this as I believe there were a few pipe-trick-related questions of SMW and SF lists as people want to hide the output.
Good point. I added a remark to the documentation (http://semantic-mediawiki.org/wiki/Help:Properties_and_types) now.