BaseModelFormset.save doesn't honor commit=False when deleting objects.

[Remoun Metyas]

When saving a ModelFormSet with some object(s) marked for deletion, calling formset.save(commit=False) still deletes the objects, which would then cause an obscure ValidationEror with invalid_choice when formset.save() is called again.

The attached patches are against trunk, but this exists as of 1.3, if not earlier.

[Remoun Metyas]

Check commit=True before deleting existing objects.

[Remoun Metyas]

Regression test.

[Adrien Lemaire]

LGTM

[Anssi Kääriäinen]

Hmmh, I think this causes problems for this common use-case:

instances = formset.save(commit=False)
for instance in instances:
    instance.user = user
    instance.save()

Currently I think things would work as follows: "deleted" instance are deleted by the formset.save(commit=False) call. The to-be-saved instances are returned, but not yet saved. After the change the deleted objects would still remain in the database after the snippet is run. Hence, the current patch is backwards incompatible.

I think a better fix would be to somehow remember that .save(commit=False) has already deleted the instances when calling the .save() again. This would get rid of the error, yet fix the problem.

[tuxcanfly]

Applied the patches and updated them according to akaariai's suggestions.

Pushed to my branch on github at: ​https://github.com/tuxcanfly/django/tree/ticket_17988

Needs review.

[Tim Graham]

Pull request for the branch: ​https://github.com/django/django/pull/165

[Kamu]

Pull request requires rebasing.

[Tim Graham]

Duplicate of #10284 which argues for changing the behavior and forcing users to handle formset.deleted_objects manually. Even though it's backwards incompatible, IMO, it's a cleaner fix as I wouldn't expect any data changing operations when using commit=False. Perhaps a django-developers discussion is needed.