BUG: If there are groups in a course you should be able to filter by them in the gradebook regardless of the groupmode settings of the various activities and the default groupmode setting at the course level.

According to the wiki the course level group mode is simple the default setting for modules, but currently it also has unintended or undocumented side effects in the gradebook:

This situation below is fairly typical for most of our HE clients:

1) courses have many groups, or multiple sets of groups / groupings, eg Campuses / Tutors / Learning Mode
2) coordinators want to be able to filter the gradebook by group (this currently requires the course groupmode = 'separate')
3) activity modules should generally NOT be in group mode, ie either the course default groupmode should be 'nogroups' or the groupmode could be forced off at course or site level.

Currently 2) and 3) are mutually exclusive but should not be.

We looked into two solutions:

A) a new feature: we split the site / course group mode settings into one for course, and one for modules. We started to implement this but this seemed overkill and made the UX a lot more complex for little benefit.

B) a bug fix: we fix the gradebook and the groups selector to allow group filtering even if the course settings is 'No groups' AND there are actually groups in the course, while still honouring the proper capability checks.

We've implemented B