You're missing the '+' or '-' to show what type of filter it is (inclusion or exclusion). Instead try this:
The filter is then applied against every search folder and because the '-' specifies an exclusion filter any folder with
generated-sources in its path would be excluded from the search.
Your regular expression
.*\\generated-sources\\.* would still work with the '-' applied, ie
-.*\\generated-sources\\.*, but the solution above is a little simpler and therefore a little faster.
To understand how Persistent Search Filters are applied imagine that they are simply appended to the end of your search path. So if you were searching in
C:\My\Folders and had both the 'SVN/HG' and 'Recycle bin' filters applied, internally the Look In functionality would be:
You may have noticed a little undocumented feature here. The filter can specify the expression type as part of the filter, in this case
:regex: specified that the filter should be treated as a regular expression. The complete list of filter expression types are:
:bool: - Boolean expression
:boolre: - Boolean RegEx
:regex: - Regular expression
:word: - Whole word
:dos: - DOS expression