Deprecate `Choices`?

[mthuurne]

Problem

I'm adding type annotations to model_utils.choices.Choices and mypy flags some errors which look like actual bugs in the code. It seems the handling of optgroups isn't implemented correctly; I'll put some examples below.

The documentation of Choices contains this note:

Django 3.0 adds enumeration types. These provide most of the same features as Choices.

Maybe Choices can be deprecated instead of fixing its implementation? I feel that would be a more efficient way of spending effort.

Environment

• Django Model Utils version: current master branch
• Django version: 4.1.7
• Python version: 3.10.6
• Other libraries used, if any: django-stubs 1.16.0

Code examples

Here the item added to triple_collector is not actually a triple:

                        # option group
                        group_name = choice[0]
                        subchoices = choice[1]
                        tc = []
                        triple_collector.append((group_name, tc))
                        dc = []
                        double_collector.append((group_name, dc))
                        self._process(subchoices, tc, dc)

Option groups in self._doubles are doubles (pairs) if they were passed to the Choices constructor as doubles, but triples if they were passed as triples. This is a result of how the _process() method handles them: triples are stored as-is whether they contain optgroups or not, while optgroups in doubles are added recursively.

Full code is here.