- In this version, abusefilter has 2 tags: "test" and "test2".
- Remove "test2" from "Tags to apply" box. There is only one tags "test".
- Click "Save filter".
- The change is not be saved.
I came across this bug by chance, but I want to spend a couple of words. Because of this use of array_diff, I also faced some troubles for T32024: the 2 arrays were different but the edit wasn't saved because array_diff didn't return true. I solved this by adding an equality check for the arrays, however limited to block action. It wouldn't be a problem to extend it to every action, and I'll probably do that if it's needed. Actually, I can't see why such simple check wasn't added in the beginning.
EDIT RIGHT BEFORE POSTING: Maybe we could be even safer by leaving array_diff as it is and adding an opposite array_diff (swapped parameters) instead of an equality check. @matej_suchanek do you think it would be fine?