FilteredSelectMultiple widget’s elements aren’t labelled

[Thibaud Colas]

In the admin UI, the FilteredSelectMultiple is missing labels for some of its elements. Here’s a recording of the widget’s UI, and what users would get for it in VoiceOver:

There are two problems here:

• "Filter edit text" – it’s not ideal for both of those to have the same label. Ideally each side would have a separate label ("Filter Available permissions", "Filter Chosen permissions"). This could be achieved with adding an aria-describedby on the filter input elements, pointing to the "Available permissions" text (and same for chosen permissions).
• "list box" – those select elements don’t have a label at all. This needs to be added by transforming the h2 elements into label, with a for pointing at each field.

In both cases it seems the fix should be implemented in [SelectFilter2.js ​https://github.com/django/django/blob/main/django/contrib/admin/static/admin/js/SelectFilter2.js#L38].

In Django itself, only contrib.auth group and user model forms use the filter_horizontal ModelAdmin API which has the issue. Not quite sure whether this widget is meant to be reused by users or not.