`transactional_db` will ignore `--keep-db` and always flush the db after the test

I haven't found this exact issue anywhere, apologies if I missed something.

My special use-case is (ab-)using pytest-django for integration tests on a real server (of course not in production) and I was using the following fixture to prevent database setup and teardown:

@pytest.fixture(scope="session")
def django_db_setup():
    return

(With the database being set up for the test in separate code.)

With the normal django_db and db markers/fixtures this works and doesn't flush the database. As soon as I add transaction=True or use transactional_db the database is always flushed.

The reason the flushing is done is that TransactionTestCase calls the flush command in its teardown method.

As a workaround I resorted to using the following fixture instead of transactional_db:

@pytest.fixture(scope="function")
def my_integration_transactional_db(request, django_db_setup,
                                     django_db_blocker):
    """cannibalized from transactional_db fixture

    but without the possible customization

     - Won't check if we're called from a django testcase

     - Won't reset sequences

     - Don't care if we're called from a live server (that's handled
       from the live_server fixture
)
     - And MOST IMPORTANTLY: won't perform teardown (NO FLUSH!)

    """

    django_db_blocker.unblock()
    request.addfinalizer(django_db_blocker.restore)

    from django.test import TransactionTestCase

    test_case = TransactionTestCase(methodName="__init__")
    test_case._pre_setup()

The most important thing here is that I skip the finalizer altogether (which works in my special use-case if database setup and teardown is done separately).

Start with the transactional_db fixture and compare its teardown behavior with django_db_setup and the --keep-db option. Read Django's TransactionTestCase teardown path, especially the flush operation, and check how transaction=True reaches it. Done means transactional_db respects --keep-db without flushing while preserving the documented fixture behavior.