Hook not firing

I verified that hook_fullcalendar_process_dates_alter() is non-functional. In the D7 versions this alter hook was invoked in the theme.inc file. It looks like that file was removed and split up during the D8 upgrade. During that process the hook invocation was lost and forgotten.

I restored the invocation, but felt like I had to update its definition. This is a BC break, but BC is broken already and has been for years. I don't think it matters and shouldn't require a new major version. Anyway, the new hook definition works better with FullCalendar::prepareEvent() because I can just plug in existing variables. I think that the context information delivers the same information that it did in D7, just maybe not quite as conveniently, i.e. the field info would have to be extracted from the fields array.

Anyway, I was able to successfully create a hook implementation with the code I've provided in the MR.

I'm setting the priority to Major since this bug renders the hook unusable with no workaround.

dcam → changed the visibility of the branch 3517066-process-dates-hook to hidden.

I hid MR 58 because there was something wrong with it. I think it was caused by me opening the MR while the issue version was set to 3.0.2. MR 59 was properly created from the 3.1.x branch.