Thread:Extension talk:CirrusSearch/Multi namespace suggest/reply

I've figured this out. The issue lies in the js call sent to the Opensearch API. Below are the tests I ran.

Tested hardcoding the namespaces array (e.g. $this->namespaces = array(0,14);) in the __construct function of CirrusSearchSearcher.php. With this in place, I can get valid suggestions from both namespaces.

Tested a query via the Opensearch API: api.php?action=opensearch&search=air&limit=10&namespace=0|14&format=json
 * With the default search enabled, only Main namespace suggestions were returned.
 * With CirrusSearch enabled, the Main and Category suggestions were returned.

Noticed that the js call to Opensearch from within the wiki always sends namespace=0. Found the file resources/mediawiki/mediawiki.searchSuggest.js and changed the hardcoded '0' to '0|14' on line 149, now I receive valid suggestions from both namespaces.

Ancient Bugzilla report on this issue: https://bugzilla.wikimedia.org/show_bug.cgi?id=24214