Application scope not behaving when searching for " " with filters

[Nick Dedekind]

1) Open app scope and empty search string
2) Type " " into search bar (space)
     You should have results
3) Enable a type filter (eg Education)
     All results disapear!
4) clear the search
     Some results, but not what we started with.

[Brandon Schaefer (brandontschaefer)]

My guess is whitespace is removed when tokenizing the search string. So changing the filter sends an empty string through (just a guess though...)

[Sami Jaktholm (sjakthol)]

The problem seems to be that a search triggered by queue_search_changed sends the whitespace only string as search term but normally Unity doesn't send whitespace only searches to scopes.

To make matters worse, app-lens doesn't consider whitespace only search as empty (in Utils.is_search_empty) and an invalid query string is generated (and the search fails):
WARNING **: Error parsing query 'type:Application AND ((category:Accessibility AND NOT category:Settings)) AND ': Syntax: <expression> AND <expression>

[Stephen M. Webb (bregma)]

Bug affects only the unity-lens-applications project, not the Unity project.