[0.91-bugfixes][patch] Admin list page for one-to-one objects breaks after viewing detail page

[Tom Tobin <korpios@…>]

On 0.91-bugfixes, the admin list view for a one-to-one related model will break after viewing an object detail page in certain cases.

How to reproduce:

1. View the detail page for a one-to-one object that does not have its "parent" relation set.
2. View the list page for the object's model; the list will only show the object viewed from the detail page until the server is restarted.

This happens because in django.core.meta.__init__'s manipulator_init function, lookup_kwargs is set to the value of opts.one_to_one_field.rel.limit_choices_to rather than .copy()-ing it. Since the function then alters lookup_kwargs — and thus limit_choices_to — to add an __exact argument for the primary key of the model, all code that subsequently checks limit_choices_to will be affected by the __exact argument.

A patch to correct the issue is attached.

[Tom Tobin <korpios@…>]

fix for Ticket #3938 (admin view bug with one-to-one models)

[James Bennett]

Fixed in [4936].