Wikimedia Bugzilla is closed!

Some research showed that this bug has been discovered before, but was never reported:

http://www.mediawiki.org/wiki/Extension_talk:Semantic_Forms/Archive_May_to_June_2011#Parser_functions_in_default_field_values

This bug is triggered when a field looks like this:

{{{field|MyPropertyName|default={{ANYTHING IN DOUBLE CURLY BRACES}}}}} (Some instruction text)

Which will produce a field that looks like this (Field shown in square brackets):

[ {{ANYTHING IN DOUBLE CURLY BRACES ]   }} (Some instruction text)

Putting a space after the template, before the closing "}}}" will resolved the problem:

{{{field|MyPropertyName|default={{ANYTHING IN DOUBLE CURLY BRACES}} }}} (Some instruction text)

This bug is triggered by templates, parser functions, magic words, and anything else that is in double curly braces. I tested all three of those, but did not test parameters, which are in triple curly braces. 

Tested:

* {{Template:Any template}}
* {{#Any: parser function}}
* {{ANYMAGICWORD}}

Not tested, but probably also triggers the bug:

* {{{Any template parameter|}}}

I assume anything in curly braces will trigger the bug. I don't think this problem is in the mediawiki parser, but I have not verified that. I think the problem is in Semantic Forms.

This problem has been giving me grief since the beginning, and I could not figure out why nothing I did ever worked. I will update the documentation with a brief explanation, and a link to this bug, so people don't get stuck.