Django: do not create migration when adding custom manager to auth.User

Question

I would like to add a custom manager to the built-in auth.User model.

I avoid switching to my own user model because of existing data in the database linking to the auth_user table.

So I add the following to models.py:

from django.contrib.auth.models import User, UserManager

class ActiveUserManager(UserManager):
    use_in_migrations = False
    def get_queryset(self):
        return super().get_queryset().filter(is_active=True)

# Monkeypatch auth.User to have custom manager
User.add_to_class('active_users', ActiveUserManager())

This seems to work, until when I run python manage.py makemigrations, Django creates a migration file 000n_auto_20181002_1721.py in myvenv/Lib/site-packages/django/contrib/auth/migrations folder, with the following content:

# imports omitted
class Migration(migrations.Migration):

    dependencies = [
        ('auth', '0008_alter_user_username_max_length'),
    ]

    operations = [
        migrations.AlterModelManagers(
            name='user',
            managers=[
                ('active_users', django.db.models.manager.Manager()),
                ('objects', django.contrib.auth.models.UserManager()),
            ],
        ),
    ]

Setting use_in_migrations = False in class ActiveUserManager does not help.

I would appreciate your suggestions on how to avoid creating this migration file or how to add a custom manager to the built-in auth.User model without this behavior. I am using Django 1.11.

Answer 1

Figured it out.

I needed to also add 'objects' manager to User class, otherwise Django treats 'active_users' as the default manager.

Full code below:

from django.contrib.auth.models import User, UserManager

class ActiveUserManager(UserManager):
    use_in_migrations = False
    def get_queryset(self):
        return super().get_queryset().filter(is_active=True)

# IMPORTANT! to add 'objects' manager
# Otherwise Django treats 'active_users' as the default manager
User.add_to_class('objects', UserManager())

# Monkeypatch auth.User to have custom manager
User.add_to_class('active_users', ActiveUserManager())

I realized this by reading ModelState.fromModel(), where 'active_users' was _default_manager when 'objects' manager was not set by User.add_to_class('objects', UserManager()).

Default manager gets added to migration even when use_in_migrations = False is set.