How to solve the problem of Dual behavior of django CustomUser in migration?

Question

I have a data migration as below in which I want to use create_user method of CustomUser, get an instance of the created user, and use this instance to create instance of Partner model. It is worth mentioning that I have a Partner model that has a one-to-one relationship with CustomUser. I have two options:

# Option One:

def populate_database_create_partner(apps, schema_editor):
    Partner = apps.get_model('partners', 'Partner')

    CustomUser.objects.create_user(
        id=33,
        email='test_email@email.com',
        password='password',
        first_name='test_first_name',
        last_name="test_last_name",
        is_partner=True,
    )

    u = CustomUser.objects.get(id=33)
    partner = Partner.objects.create(user=u, )


class Migration(migrations.Migration):

    dependencies = [
        ('accounts', '0006_populate_database_createsuperuser'),
    ]

    operations = [
        migrations.RunPython(populate_database_create_partner),
    ]

In option one, I see this error:

ValueError: Cannot assign "<CustomUser: test_email@email.com>": "Partner.user" must be a "CustomUser" instance.

I then test this:

# Option Two:

def populate_database_create_partner(apps, schema_editor):
    Partner = apps.get_model('partners', 'Partner')
    CustomUser = apps.get_model('accounts', 'CustomUser')


    CustomUser.objects.create_user(
        id=33,
        email='test_email@email.com',
        password='password',
        first_name='test_first_name',
        last_name="test_last_name",
        is_partner=True,
    )

    u = CustomUser.objects.get(id=33)
    partner = Partner.objects.create(user=u, )


class Migration(migrations.Migration):

    dependencies = [
        ('accounts', '0006_populate_database_createsuperuser'),
    ]

    operations = [
        migrations.RunPython(populate_database_create_partner),
    ]

I the see this error:

CustomUser.objects.create_user(
AttributeError: 'Manager' object has no attribute 'create_user'

The create_user method does not work.

If I do not use the create_user method and simply use CustomUser.objects.create(...), I will not be able to set password in here.

also you can try `partner = Partner.objects.create(user_id=33, )` in the first solution — Brown Bear, Oct 09 '19 at 11:29
Put it this way, If I use the model through import, I will be able to use its methods. If I import them through apps.get_model, then methods do not work — Amin Ba, Oct 09 '19 at 11:29
I encountered another issue. My Partner model has a custom save method that creates a slug. the slug is not created, because of the same issue! Methods does not work!!! — Amin Ba, Oct 09 '19 at 11:36

score 0 · Accepted Answer · answered Oct 09 '19 at 13:58

Django only keeps limited historical information about each version of your models. One of the things it doesn't keep track of, as documented here, is custom model managers.

The good news is that there's a way to force the migrations system to use your custom manager:

You can optionally serialize managers into migrations and have them available in RunPython operations. This is done by defining a use_in_migrations attribute on the manager class.

As noted, this just allows your migration to use the version of the manager that exists when the migration is run; so, if you later make changes to it, you could break the migration. A safer alternative is to just copy the relevant create_user code into the migration itself.

How to solve the problem of Dual behavior of django CustomUser in migration?

1 Answers1