Django 2.1 how do I create a user in a migration

Question

I'm trying to add a new user and then associate it to a subset of existing records.

For example, imagine I have this app model:

class Foo(Model):
    user = model.ForeignKey(User, default=None, on_delete=models.CASCADE)

In my migration I have:

from django.contrib.auth.models import User    

def add_user(apps, schema_editor):
    anon = User.objects.create_user(username='anonymous')
    anon.save()

    Foo = apps.get_model('myapp', 'Foo')
    foo_to_change = Foo.objects.filter(user_id=1)

    for f in foo_to_change:
        f.user = anon
        f.save()    

When I run this I get this error:

ValueError: Cannot assign "<User: anonymous>": "Foo.user" must be a "User" instance.

I thought the problem might be that I'm using the User model directly and the docs say not to do this. So I changed the top part to:

User = apps.get_model('auth', 'User')
anon = User.objects.create_user(username='anonymous')
anon.save()

Now I get a different error:

AttributeError: type object 'User' has no attribute 'normalize_username'

What am I doing wrong? How do I add a new user in a data migration?

EDIT: I'm using sqlite as DB

Answer 1

You can do something like:

def add_user(apps, schema_editor): 
    apps.get_model('myapp', 'Foo').objects.filter(user_id=1).update(
        user=apps.get_model('auth', 'User').objects.create_user(username='anonymous')
    )

This works because in this case "no type is checked", the query will use a reference to the entry in the DB instead: the ID of the user.