Fixed #29987 -- Detected unmanaged model deletions.

[0x68]

This should fix the problem reported in issue #29987. This is my first contribution on the project. Therfore I have to spend some more time as expected on the tests. I have only used pytest so far

[charettes]

Hey @0x68! The test should live in test_autodetector.py.

You should be able to create a tests by setting up a from_state and to_state and assert against the from changes = self.get_changes(from_state, to_state).

[0x68]

I have read about the documentation. Seems to be a feature not a bug.

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

[charettes]

@0x68 the removal of the model should still be tracked. It will result in a noop SQL operation because the model is not managed though.

In other words, the DeleteModel operation should be added to denote the unmanaged model removal from the project state. On application it won't result in any SQL though.

[charettes]

Here's what causes the actual DROP TABLE to be skipped

django/django/db/migrations/operations/models.py

Line 260 in f091ea3

if self.allow_migrate_model(schema_editor.connection.alias, model):

django/django/db/migrations/operations/base.py

Lines 111 to 112 in f091ea3

	if not model._meta.can_migrate(connection_alias):
	return False

django/django/db/models/options.py

Lines 305 to 306 in f091ea3

	if self.proxy or self.swapped or not self.managed:
	return False