Opened 3 years ago

Closed 2 years ago

#17988 closed Bug (duplicate)

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

Reported by: rem Owned by: tuxcanfly
Component: Forms Version: 1.3
Severity: Normal Keywords:
Cc: lemaire.adrien@…, akaariai, tuxcanfly, timograham@… Triage Stage: Accepted
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: yes UI/UX: no

Description

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.

Attachments (2)

model_formset_check_commit_before_delete.diff (598 bytes) - added by rem 3 years ago.
Check commit=True before deleting existing objects.
test_model_formset_checks_commit_before_delete.diff (1.7 KB) - added by rem 3 years ago.
Regression test.

Download all attachments as: .zip

Change History (9)

Changed 3 years ago by rem

Check commit=True before deleting existing objects.

Changed 3 years ago by rem

Regression test.

comment:1 Changed 3 years ago by Fandekasp

  • Cc lemaire.adrien@… added
  • Needs documentation unset
  • Needs tests unset
  • Patch needs improvement unset
  • Triage Stage changed from Unreviewed to Accepted

LGTM

comment:2 Changed 3 years ago by akaariai

  • Cc akaariai added
  • Patch needs improvement set

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.

comment:3 Changed 3 years ago by tuxcanfly

  • Cc tuxcanfly added
  • Owner changed from nobody to tuxcanfly
  • Patch needs improvement unset
  • Status changed from new to assigned
  • Type changed from Uncategorized to Bug

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.

comment:4 Changed 2 years ago by timo

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

comment:5 Changed 2 years ago by Kamu

Pull request requires rebasing.

comment:6 Changed 2 years ago by timo

  • Cc timograham@… added

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.

comment:7 Changed 2 years ago by timo

  • Resolution set to duplicate
  • Status changed from assigned to closed
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