[Django] #35410: Can't Set a Default Value for ForeignKey Field in Custom User Model

[Django]

#35410: Can't Set a Default Value for ForeignKey Field in Custom User Model
-------------------------------------+-------------------------------------
Reporter: Ebram | Owner: nobody
Shehata |
Type: Bug | Status: new
Component: | Version: 5.0
contrib.auth | Keywords: migrations,
Severity: Normal | foreignkey, user, models
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
Hello,

So, I'm trying to add a `ForeignKey` field with a default value in a
custom user model.
The use case is that each user should be assigned to a department. But all
new users
should have a default department with name 'UNASSIGNED'.

- How to reproduce:
1. Create a blank Django project.
2. Create a new 'profiles' app.
3. Register the app in settings.py and point `AUTH_USER_MODEL` to
`"profiles.UserProfile"`.

{{{
INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
"profiles"
]
AUTH_USER_MODEL = "profiles.UserProfile"
}}}

4. Add the following models to profiles/models.py:

{{{
from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin

from django.db import models


class Department(models.Model):
name = models.CharField(max_length=256, unique=True)


def unassigned_department():
return Department.objects.get_or_create(name="UNASSIGNED")[0].pk


class UserProfile(AbstractBaseUser, PermissionsMixin):
department = models.ForeignKey(
Department,
on_delete=models.CASCADE,
default=unassigned_department,
related_name="user_profiles",
)
username = models.CharField(max_length=256, unique=True)

is_active = models.BooleanField(default=True, null=False)
is_superuser = models.BooleanField(default=False, null=False)
is_staff = models.BooleanField(default=False, null=False)

USERNAME_FIELD = "username"
}}}

5. Run `python manage.py makemigrations`.

You'll get the following error:
`django.db.utils.OperationalError: no such table: profiles_department`

Django versions I tried: 4.2.7 and 5.0.4.

I also noticed that if I inherit from `django.db.models.Model` in
`UserProfile` de-register it
from `AUTH_USER_MODEL` setting, I can create migrations successfully and
migrate the
database too! I also could create instances that have the default
department as expected.
--
Ticket URL: <https://code.djangoproject.com/ticket/35410>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#35410: Can't Set a Default Value for ForeignKey Field in Custom User Model
-------------------------------------+-------------------------------------

Reporter: Ebram Shehata | Owner: nobody
Type: Bug | Status: closed
Component: contrib.auth | Version: 5.0
Severity: Normal | Resolution: invalid
Keywords: migrations, | Triage Stage:
foreignkey, user, models | Unreviewed
Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Tim Graham):

* resolution: => invalid
* status: new => closed

Comment:

You didn't provide the full traceback but I suspect the error comes from
`Department.objects.get_or_create()`. I don't think Django is at fault.
You could make the migrations in two steps, adding the `default` only
after the `Department` table is created.
--
Ticket URL: <https://code.djangoproject.com/ticket/35410#comment:1>

[Django]

#35410: Can't Set a Default Value for ForeignKey Field in Custom User Model
-------------------------------------+-------------------------------------
Reporter: Ebram Shehata | Owner: nobody
Type: Bug | Status: closed
Component: contrib.auth | Version: 5.0
Severity: Normal | Resolution: invalid
Keywords: migrations, | Triage Stage:
foreignkey, user, models | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Old description:

New description:

Here's the full traceback:

{{{
Traceback (most recent call last):
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/utils.py", line 105, in _execute
return self.cursor.execute(sql, params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/sqlite3/base.py", line 329, in execute
return super().execute(query, params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
sqlite3.OperationalError: no such table: profiles_department

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/SOME-DIR/blank_django/src/blanked/manage.py", line 22, in
<module>
main()
File "/SOME-DIR/blank_django/src/blanked/manage.py", line 18, in main
execute_from_command_line(sys.argv)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/__init__.py", line 442, in
execute_from_command_line
utility.execute()
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/__init__.py", line 436, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/base.py", line 413, in run_from_argv
self.execute(*args, **cmd_options)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/base.py", line 454, in execute
self.check()
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/base.py", line 486, in check
all_issues = checks.run_checks(
^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/checks/registry.py", line 88, in run_checks
new_errors = check(app_configs=app_configs, databases=databases)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/contrib/auth/checks.py", line 84, in check_user_model
if isinstance(cls().is_anonymous, MethodType):
^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/base.py", line 535, in __init__
val = field.get_default()
^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/fields/related.py", line 1134, in get_default
field_default = super().get_default()
^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/fields/__init__.py", line 1021, in get_default
return self._get_default()
^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/blanked/profiles/models.py", line 11,
in unassigned_department

return Department.objects.get_or_create(name="UNASSIGNED")[0].pk

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/manager.py", line 87, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/query.py", line 948, in get_or_create
return self.get(**kwargs), False
^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/query.py", line 645, in get
num = len(clone)
^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/query.py", line 382, in __len__
self._fetch_all()
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/query.py", line 1928, in _fetch_all
self._result_cache = list(self._iterable_class(self))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/query.py", line 91, in __iter__
results = compiler.execute_sql(
^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/models/sql/compiler.py", line 1562, in execute_sql
cursor.execute(sql, params)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/utils.py", line 122, in execute
return super().execute(sql, params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/utils.py", line 79, in execute
return self._execute_with_wrappers(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/utils.py", line 92, in _execute_with_wrappers
return executor(sql, params, many, context)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/utils.py", line 100, in _execute
with self.db.wrap_database_errors:
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/utils.py", line 91, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/utils.py", line 105, in _execute
return self.cursor.execute(sql, params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/backends/sqlite3/base.py", line 329, in execute
return super().execute(query, params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

django.db.utils.OperationalError: no such table: profiles_department

}}}

--
Comment (by Ebram Shehata):

Replying to [comment:1 Tim Graham]:

> You didn't provide the full traceback but I suspect the error comes from
`Department.objects.get_or_create()`. I don't think Django is at fault.
You could make the migrations in two steps, adding the `default` only
after the `Department` table is created.

Oh, I just added the traceback.

- I think that is not the expected behavior when someone uses a callable
as `default` parameter. I expect it to be used when the value was not
provided and I'm trying to create an instance and of course not when I
make migrations and that is working as expected when the target model is
not a custom user model (inheriting from `models.Model`).

- I also think the work around of creating a data migration for creating
the default instance is not actually convenient. Because I think the
scenario could be:
Develop stuff.
Create migration for the project and the a special migration for that
default instance.
After that we'll have to actually migrate the database so far to create
that instance.
Now develop the custom user profile and make migrations.
Now we should be able to migrate database but no. Here's a problem that
appeared with this scenario after adding the custom user model in this
case:

{{{
Operations to perform:
Apply all migrations: admin, auth, contenttypes, profiles, sessions
Traceback (most recent call last):
File "/SOME-DIR/blank_django/src/blanked/manage.py", line 22, in
<module>
main()
File "/SOME-DIR/blank_django/src/blanked/manage.py", line 18, in main
execute_from_command_line(sys.argv)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/__init__.py", line 442, in
execute_from_command_line
utility.execute()
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/__init__.py", line 436, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/base.py", line 413, in run_from_argv
self.execute(*args, **cmd_options)
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/base.py", line 459, in execute
output = self.handle(*args, **options)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/base.py", line 107, in wrapper
res = handle_func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/core/management/commands/migrate.py", line 302, in handle
pre_migrate_apps = pre_migrate_state.apps
^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/utils/functional.py", line 47, in __get__
res = instance.__dict__[self.name] = self.func(instance)
^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/migrations/state.py", line 566, in apps
return StateApps(self.real_apps, self.models)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/SOME-DIR/blank_django/src/venv/lib/python3.11/site-
packages/django/db/migrations/state.py", line 637, in __init__
raise ValueError("\n".join(error.msg for error in errors))
ValueError: The field admin.LogEntry.user was declared with a lazy
reference to 'profiles.userprofile', but app 'profiles' doesn't provide
model 'userprofile'.
}}}


Overall about the scenario of having to create a data migration for that
default instance, I think it's not convenient and it is not what's
expected from a callable in `default` parameter. I think it should be
behaving the same as with regular models, not having a special behavior if
we're creating a custom user model.
--
Ticket URL: <https://code.djangoproject.com/ticket/35410#comment:2>

[Django]

#35410: Can't Set a Default Value for ForeignKey Field in Custom User Model
-------------------------------------+-------------------------------------
Reporter: Ebram Shehata | Owner: nobody
Type: Bug | Status: closed
Component: contrib.auth | Version: 5.0
Severity: Normal | Resolution: invalid
Keywords: migrations, | Triage Stage:
foreignkey, user, models | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Simon Charette):

Maybe I ask you are not simply `NULL` to denote the lack of assignment?
--
Ticket URL: <https://code.djangoproject.com/ticket/35410#comment:3>