ManyToManyField to lowercased swappable setting causes generating infinite migrations.

[Chris Lee]

If I create a custom user model that extends AbstractUser and then try to add a ManyToManyField that references this custom User model, django keeps making the same AlterField migration over and over again unnecessarily. I've attached a Git repository that I used to reproduce this issue with very simple code. You can see the two erroneous migrations after the initial migration. If I use the built in user, there is no issue. It seems to appear once I extend AbstractUser.

Git repository: ​https://github.com/SentientClee/django-bug-reproduction

Here is the accounts app model.py code.

from django.conf import settings
from django.contrib.auth.models import AbstractUser
from django.db import models


class User(AbstractUser):
    pass


class Test(models.Model):
    members = models.ManyToManyField(settings.AUTH_USER_MODEL)

Here is one of the erroneous migrations. Notice it depends on 0002_alter_test_members which is an erroneous migrations file that looks just like this one.

# Generated by Django 4.0.2 on 2022-02-15 01:33

from django.conf import settings
from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('accounts', '0002_alter_test_members'),
    ]

    operations = [
        migrations.AlterField(
            model_name='test',
            name='members',
            field=models.ManyToManyField(to=settings.AUTH_USER_MODEL),
        ),
    ]

[Mariusz Felisiak]

Thanks for the report!

Lowercased AUTH_USER_MODEL = 'accounts.user' is crucial to reproduce this issue.

Regression in 43289707809c814a70f0db38ca4f82f35f43dbfd.

[Mariusz Felisiak]

​PR

[GitHub <noreply@…>]

In 1e2e1be:

Fixed #33515 -- Prevented recreation of migration for ManyToManyField to lowercased swappable setting.

Thanks Chris Lee for the report.

Regression in 43289707809c814a70f0db38ca4f82f35f43dbfd.

Refs #23916.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 760b7e7f:

[4.0.x] Fixed #33515 -- Prevented recreation of migration for ManyToManyField to lowercased swappable setting.

Thanks Chris Lee for the report.

Regression in 43289707809c814a70f0db38ca4f82f35f43dbfd.

Refs #23916.
Backport of 1e2e1be02bdf0fe4add0d0279dbca1d74ae28ad7 from main