Opened 3 years ago

Closed 2 years ago

Last modified 4 months ago

#32833 closed Bug (fixed)

ContentType.objects.get_for_models() in migrations does not works for multiple models

Reported by: HMaker Owned by: Sarah Boyce
Component: contrib.contenttypes Version: 3.1
Severity: Normal Keywords:
Cc: Triage Stage: Ready for checkin
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description (last modified by HMaker)

I am trying to use migrations to create default groups, I tried to run the following procedure with migrations.RunPython()

def create_normal_users_group(apps, *args):
    auth = SimpleNamespace(**apps.all_models['auth'])
    myapp = SimpleNamespace(**apps.all_models['myapp'])
    ContentType = apps.get_model('contenttypes', 'ContentType')
    group = auth.group.objects.create(name='Normal Users')
    contenttypes = ContentType.objects.get_for_models(myapp.user, myapp.proxy) # there are more models...
   # ...

but it raises AttributeError

  File "/home/user/projects/myapp/.venv/lib/python3.8/site-packages/django/contrib/contenttypes/models.py", line 89, in get_for_models
    opts_models = needed_opts.pop(ct.model_class()._meta, [])
AttributeError: 'ContentType' object has no attribute 'model_class'

it works when I pass a single model to ContentType.objects.get_for_models(), but get_for_models() is supposed to work with multiple models.

EDIT:
Adding model_class() to ContentType makes it work

def create_normal_users_group(apps, *args):
    auth = SimpleNamespace(**apps.all_models['auth'])
    myapp = SimpleNamespace(**apps.all_models['myapp'])
    ContentType = apps.get_model('contenttypes', 'ContentType')
    # this makes it work =========================
    def model_class(self):
        return apps.get_model(self.app_label, self.model)
    ContentType.model_class = model_class
    # ========================================
    group = auth.group.objects.create(name='Normal Users')
    contenttypes = ContentType.objects.get_for_models(myapp.user, myapp.proxy) # there are more models...
   # ...

Change History (15)

comment:1 by HMaker, 3 years ago

Description: modified (diff)

comment:2 by Simon Charette, 3 years ago

Triage Stage: UnreviewedAccepted

Since ContentTypeManager is marked as use_in_migrations = True it should be able to handle this case.

There's two possible solutions here:

  1. Create an AbstractContentType(models.Model) abstract model class that include most of the logic ContentType and have the latter subclass the former. From there CreateModel(bases) should be adjusted to pass this base instead.
  2. Adjust ContentTypeManager.get_for_models to avoid calling .model_class() and inline its logic in the manager method instead.

Feels like 2. is the less disruptive approach and easier to test. Would you be interested in writing a patch PR for it?

comment:3 by HMaker, 3 years ago

Owner: changed from nobody to HMaker
Status: newassigned

OK I will implement 2nd solution.

comment:4 by HMaker, 3 years ago

I tried to reproduce this problem but I could not, check my partial patch, it's based on 3.1.4 branch.

comment:5 by HMaker, 3 years ago

Has patch: set
Patch needs improvement: set

in reply to:  4 comment:6 by Keryn Knight, 3 years ago

Replying to Heraldo Lucena:

I tried to reproduce this problem but I could not [...]

My guess would be that the ContentTypeManager instance already had a partially filled (or empty) cache when you encountered the error, such that self._get_from_cache(modelinstance._meta) worked (didn't throw a KeyError looking in the self._cache).

  • If you pass in 2 model classes Group and User and both are already in its internal cache, then needed_opts is empty and needed_opts.pop(ct.model_class()._meta, []) doesn't occur.
  • If you pass the same 2 classes and only 1 or 0 of them are in the self._cache already, you'd fill the missing items into needed_opts and hit the line which has caused you problems.

comment:7 by HMaker, 3 years ago

I thought migrations would be automatically rolled back after each test case, but that did not happen and last test case could not run properly since all migrations were already applied. Now the regression test can reproduce reported problem.

PR made.

Last edited 3 years ago by HMaker (previous) (diff)

comment:8 by HMaker, 3 years ago

Patch needs improvement: unset

comment:9 by Mariusz Felisiak, 3 years ago

Patch needs improvement: set

comment:10 by Mariusz Felisiak, 2 years ago

Owner: HMaker removed
Status: assignednew

comment:11 by Sarah Boyce, 2 years ago

Owner: set to Sarah Boyce
Patch needs improvement: unset
Status: newassigned

comment:12 by Mariusz Felisiak, 2 years ago

Triage Stage: AcceptedReady for checkin

comment:13 by GitHub <noreply@…>, 2 years ago

Resolution: fixed
Status: assignedclosed

In 84206607:

Fixed #32833 -- Fixed ContentTypeManager.get_for_models() crash when using in migrations.

Co-authored-by: Heraldo Lucena <23155511+HMaker@…>

comment:14 by Sarah Boyce <42296566+sarahboyce@…>, 4 months ago

In f1705c8:

Fixed #35545, Refs #32833 -- Fixed ContentTypeManager.get_for_models() crash in CreateModel migrations.

Thank you to Csirmaz Bendegúz for the report and Simon Charettes for the review.

comment:15 by Sarah Boyce <42296566+sarahboyce@…>, 4 months ago

In 6317803:

[5.1.x] Fixed #35545, Refs #32833 -- Fixed ContentTypeManager.get_for_models() crash in CreateModel migrations.

Thank you to Csirmaz Bendegúz for the report and Simon Charettes for the review.

Backport of f1705c8780c0a7587654fc736542d55fe4a7f29b from main.

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