Add a better error messsage or an FAQ entry for InvalidBasesError

[David Burke]

Extend the User model using this method

from django.contrib.auth.models import User

class Faculty(User):
    foo = models.CharField(max_length=10)

In 1.7 beta 4 this works. With 1.7RC1 I get:

Running migrations:
  Applying contenttypes.0001_initial...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 337, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 160, in handle
    executor.migrate(targets, plan, fake=options.get("fake", False))
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 62, in migrate
    self.apply_migration(migration, fake=fake)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 90, in apply_migration
    if self.detect_soft_applied(migration):
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 134, in detect_soft_applied
    apps = project_state.render()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/state.py", line 71, in render
    raise InvalidBasesError("Cannot resolve bases for %r" % new_unrendered_models)
django.db.migrations.state.InvalidBasesError: Cannot resolve bases for [<django.db.migrations.state.ModelState object at 0x7f5d6af3ad50>]

[David Burke]

To reproduce you must not have 1.7 migrations for the app. On a app created with 1.7 you can just remove the migrations folder. I noticed the problem when trying 1.7 on an existing <1.7 django app and creating a fresh database with migrate.

[Tim Graham]

You cannot have apps without migrations depend on apps with migrations which I think is the issue here. See ​https://docs.djangoproject.com/en/dev/topics/migrations/#dependencies

It may be worth trying to raise a more useful error message, however.

[Andrew Godwin]

Promoting to release blocker so we don't get more tickets like #22965.

[Andrew Godwin <andrew@…>]

In b02abd688a60e2dedf607e34d2cc97aca8d1c2b5:

Fixed #22922: Better error message for InvalidBasesError.

[Andrew Godwin <andrew@…>]

In 23ff98888e5c183b299f29ea651c9b545ef02807:

[1.7.x] Fixed #22922: Better error message for InvalidBasesError.

[Mathieu Agopian]

I'd like to reopen this, as I believe the error message in its current state isn't very useful.
However, I'm not sure it's a good idea to reopen it, as this ticket is a release blocker, and an "even better" error message maybe isn't that important ;)

Here's an example output:

Cannot resolve bases for [<django.db.migrations.state.ModelState object at 0x7fd8e82f45d0>, <django.db.migrations.state.ModelState object at 0x109b8e69f476>]
This can happen if you are inheriting models from an app with migrations (e.g. contrib.auth)
 in an app with no migrations; see https://docs.djangoproject.com/en/1.7/topics/migrations/#dependencies for more

I think it would be much more useful to have the model names for which the bases could not be resolved, eg:

['foo.Bar', 'baz.Cruux']

A proposed modification would be to pass in ['{}.{}'.format(ms.app_label, ms.name) for ms in new_unrendered_models] instead of simply new_unrendered_models.

As a side note, I'm not sure the space in front of " in an app" should be there, as it's just after a line-jump, it could (should?) be removed (just nitpicking ;).

[spam@…]

I have analog example.Solved with remove from class Meta attribute 'abstract=True' in one is many classes (Sorry for my English,this is not my native language =) )

[Simon Charette]

From what I understand you might be hitting a completely different issue.

Please don't re-open fixed tickets but open a new one with a detailed report.