id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
22838	Deprecate ModelChoiceField.cache_choices	Marc Tamlyn	nobody	"`ModelChoiceField` (and `MultipleModelChoiceField`) take an option `cache_choices`. This was introduced as a backwards compatibility effort in February 2007 (ee96c7eb2dea86e5bdaf93f7afa91b6f0128dd72) when the fields were made to not always cache their choices (#3534).

The option is undocumented, untested and unused within Django.

There are two possible courses of action here.

Firstly, we could simply remove the option. It should have a deprecation cycle - in particular for people with custom subclasses of `ModelChoiceField` who pass in the option to the super.

The alternative course of action which I prefer is to harden this into an actual feature. It already works as follows:
- Create the `ModelChoiceField` with `cache_choices=True`.
- The `ModelChoiceIterator` will cache its results on the `ModelChoiceField` and use that cache.

What would be needed to make this a fully fledged feature in my opinion:
- An API to clear the cache (`ModelChoiceField.clear_cache()`)
- [Very possibly] Plug it in to the cache framework properly
- Tests
- Documentation

I think this would be a very useful feature, and one which I have had use cases for often. The most obvious use cases is when working with the same form multiple times on a page (either as part of a formset or not) the same query is run for every form. I can call `MyForm.fields['modelchoicefield'].clear_cache()` after all the forms are rendered.

The biggest possible issue here is that the iterator is not used until the form is rendered. We may need to change when the iterator is evaluated for this case.

I may be able to provide a patch if the feature is accepted."	Cleanup/optimization	closed	Forms	dev	Normal	fixed			Ready for checkin	1	0	0	0	0	0