order_by parameter for inlineformset_factory and BaseInlineFormSet

[Paulo Scardine <paulo@…>]

Problem

At inlineformset_factory and BaseInlineFormSet constructor there is no option to specify order_by criteria for the resulting queryset.

The record order at the rendered formset will depend on the order returned by the database layer; notably PostgreSQL may change this order after every update. When using PRG (Post/Redirect/Get) the result is unpleasant and may confuse users.

Proposed Solution

I would like to add an order_by parameter to inlineformset_factory and BaseInlineFormSet.

[Paulo Scardine <paulo@…>]

Patch to add order_by parameter for inlineformset_factory

[Carl Meyer]

Related: #9758, #9006.

[Alex Gaynor]

marking as design decision needed, why not just pass the queryset already ordered?

[anonymous]

At first it also looked like a good idea to pass a queryset ready.

But giving it some thought to this issue, my opinion changed. I think the purpose of inlineformset_factory is very specific: making a formset linked by the parent_model PK.

So what is the point of passing a queryset as argument? If it is for flexibility, it seems out of place, because we should address the common use case and not the exception.

If you could make the point for a broader solution I will be happy to provide a patch.

[paulos]

New patch as sugested by Alex

[paulos]

New patch adds a queryset argument to BaseInlineFormSet making it consistent with BaseModelFormset, as sugested by Alex.

[paulos]

Chained the fk filter even if queryset provided, as sugested by Alex.

[paulos]

Last patch is a little better styled (won't trigger evaluation).

[Russell Keith-Magee]

(In [11874]) Fixed #10263 -- Added a queryset argument to BaseInlineFormSet, normalizing with BaseModelFormSet, and allowing for custom ordering/subsets in inlines. Thanks to Paulo Scardine for the patch.