In some cases, when having multiple tag filters selected and results in the list, deselecting one of the filters would cause no results. This is clearly incorrect behavior, as fewer filters should lead to more (or at least the same number of) results.
This happens when you have a list of selected filters, e.g. `foo|bar|baz`, and you deselect the "middle" one. This will result in the following filter: `foo||baz`, which causes the back-end to try and filter on empty string as well, and in turn leads to no results.
The order of the filter list depends on the order they were selected, which caused this to seem a bit erratic.
In the code, there's a regular expression that tries to remove consecutive `|` characters, but this is anchored to the beginning of the string, so it doesn't work for this case.
Instead of relying on a regular expression, this change splits the string into an array, filters out the deselected tag, and joins it back together into the filter string. This avoids the issues that regular expressions have.
The PR also includes unit tests for the three code paths of the filter selection.
Jarek Radosz
Ted Johansson