Deleting non-managed model does not generate a DeleteModel in migrations

[Daniel Bowring]

If you have a model like:

class NonManagedModel(models.Model):
    some_field = models.TextField()

    class Meta:
        managed = False

and run makemigrations, a migration including a CreateModel will be generated

$ python3 manage.py makemigrations nmapp
Migrations for 'nmapp':
  nmapp/migrations/0001_initial.py
    - Create model NonManagedModel

However, if you remove the model from models.py, no migration with a DeleteModel is created

$ python3 manage.py makemigrations nmapp
No changes detected in app 'nmapp'

It seems like the intention was to include this for unmanaged models, but is being skipped (see ​django.db.migrations.autodetector)

[Simon Charette]

I haven't reproduced but looking at the auto-detector code that seems like a legitimate report. Would you be interested in providing a patch to get it fixed?

[Tim Fiedler]

I had provide a PR which for sure needs some tests. But to be honest now i'm thinking of the idea of a unmanaged model. Or to be precise... Is this a realy a bug ? Regarding the Documentation this seems to be a desired behaviour:)

​https://docs.djangoproject.com/en/2.1/ref/models/options/

If False, no database table creation or deletion operations will be performed for this model. This is useful if the model represents an existing table or a database view that has been created by some other means. This is the only difference when managed=False. All other aspects of model handling are exactly the same as normal. This includes

[Simon Charette]

Thanks for the quick patch Tim!

Left a few comments for improvement on the PR. Please uncheck Patch needs improvement once you've addressed them.

Thanks!

[Tim Graham <timograham@…>]

In b07273a:

Fixed #29987 -- Detected unmanaged model deletions.

[Andi Albrecht]

Shouldn't this be mentioned in the release notes for 2.2? It took me a while to figure out why I have new migrations after upgrading to 2.2.

[Mariusz Felisiak]

Bugfixes are not mentioned in release notes for major releases.