Source filter disappears when "Program" is selected under Category filter. Even though Programs can be associated with Sources in its settings.
Learning Management System.
Reproducing the Issue
1 - Create any Program (make sure to include it in a Catalog where it can be searched)
2 - Go to Program Settings
3 - Associate a Source for that Program
4 - Go to the User side.
5 - Click on "Browse All"
6 - In the left side, select "Program" under Category (you will notice that Source filters will be removed).
When programs were originally added they were not technically items and did not support many of the data points that items support. For that reason the search was designed to remove source for programs. Since no programs supported that data point, it didn't matter that the criteria was technically specified as part of the search.
Later program was converted to a full fledged item, but source support was never added to the catalog search due to resources and priorities. Because it now has the data point, if the criteria is supplied, the search will use it and it will work, however, it is technically an unsupported feature.
This might be considered a future enhancement by Product Management, but still no plans to include it in the roadmap.
Programs, Catalog Filters, Search Filters, Source filter disappears, Program Category removes Source filter