"makeviewmigrations --check --dry-run" fails when using "ContentType" in auto-generated DB View migrations on an unmigrated database

[gabo-magnet]

When using django_db_views to generate database view migrations that rely on django.contrib.contenttypes.models.ContentType, running python manage.py makeviewmigrations --check --dry-run on a fresh database (without applying migrations) results in the following error:

psycopg.errors.UndefinedTable: relation "django_content_type" does not exist

This issue occurs because the auto-generated migration includes a query that references the django_content_type table, which does not exist in a freshly migrated database. Since CI/CD pipelines often use makeviewmigrations --check --dry-run to verify pending migrations without applying them, this leads to an unexpected failure.

Steps to Reproduce:

1. Install django_db_views in a Django project.
2. Create a DBView model that references ContentType in a query.
3. Allow django_db_views to auto-generate a migration that includes this model.
4. Run python manage.py makeviewmigrations --check --dry-run on a fresh database.

Example Code:

DB View Model Using ContentType

from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.db.models import F, Value
from django_db_views.db_view import DBView

class ExampleDBView(DBView):
    @classmethod
    def view_definition(cls):
        queryset = (
            ExampleModel.objects.annotate(
                object_id=F("id"),
                content_type_id=Value(ContentType.objects.get_for_model(ExampleModel).id)
            ).values("object_id", "content_type_id")
        )
        return str(queryset.query)

    class Meta:
        managed = False
        db_table = "example_db_view"

In this example, the view relies on ContentType.objects.get_for_model() to include the content_type_id in the query. The auto-generated migration from django_db_views will include a ViewRunPython operation with this query.

Auto-Generated Migration (example of what might be auto-generated)

from django.db import migrations
import django_db_views.migration_functions
import django_db_views.operations

class Migration(migrations.Migration):
    dependencies = [
        ("contenttypes", "0002_remove_content_type_name"), # added this by hand
    ]

    operations = [
        django_db_views.operations.ViewRunPython(
            code=django_db_views.migration_functions.ForwardViewMigration(
                '...'
                "example_db_view",
                engine="django.db.backends.postgresql",
            ),
            reverse_code=django_db_views.migration_functions.BackwardViewMigration(
                "",
                "example_db_view",
                engine="django.db.backends.postgresql",
            ),
            atomic=False,
        ),
    ]

Expected Behavior:

• makeviewmigrations --check --dry-run should not fail if the contenttypes app has not yet been migrated.

Actual Behavior:

Running makeviewmigrations --check --dry-run results in a ProgrammingError because the django_content_type table is missing, as the database has not been migrated yet.

Workarounds Tried:

• Ensuring that contenttypes is included in the migration dependencies (did not solve the issue).
• Running migrate before makeviewmigrations --check --dry-run (works but defeats the purpose of checking migrations in CI).

Environment:

• Django version: 4.2.16
• Python version: 3.10.16
• Database: PostgreSQL
• django-db-views version: 0.1.9
• psycopg version: 3.1.20

Additional Context:

This issue is particularly relevant in CI/CD workflows where the goal is to check for pending migrations without applying them. The current behavior prevents running makeviewmigrations --check --dry-run unless the database has already been migrated, which is counterproductive.

Would it be possible for django_db_views to modify the auto-generated migrations to account for cases where the django_content_type table doesn't exist, or offer a way to handle these queries differently in an unmigrated database?

[gabo-magnet]

Additional Notes:

It’s also worth mentioning that running the following commands does not trigger the error:

• python manage.py makemigrations --check --dry-run
• python manage.py makemigrations

Both of these commands work fine, even in an unmigrated database. The error only occurs when using python manage.py makeviewmigrations or python manage.py makeviewmigrations --check --dry-run, which rely on the auto-generated migration views involving ContentType.

This distinction may help isolate the issue to the makeviewmigrations management command.

[BezBartek]

@gabo-magnet
Thank you for report, I will look into that