#24291: Migrations fail with unused swappable model
----------------------------+--------------------
Reporter: knbk | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
An unused swappable model has no managers, but when trying to migrate the
app containing that model,
`django.db.migrations.state.ModelState.from_model` is called. That method
expects the model to have at least a `_default_manager`. As this isn't the
case, an `AttributeError` is raised:
{{{
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File
"/home/s120374/projects/dev/django/django/core/management/__init__.py",
line 330, in execute_from_command_line
utility.execute()
File
"/home/s120374/projects/dev/django/django/core/management/__init__.py",
line 322, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/s120374/projects/dev/django/django/core/management/base.py",
line 350, in run_from_argv
self.execute(*args, **cmd_options)
File "/home/s120374/projects/dev/django/django/core/management/base.py",
line 401, in execute
output = self.handle(*args, **options)
File
"/home/s120374/projects/dev/django/django/core/management/commands/migrate.py",
line 173, in handle
ProjectState.from_apps(apps),
File "/home/s120374/projects/dev/django/django/db/migrations/state.py",
line 94, in from_apps
model_state = ModelState.from_model(model)
File "/home/s120374/projects/dev/django/django/db/migrations/state.py",
line 348, in from_model
default_manager_name = model._default_manager.name
AttributeError: type object 'Swappable' has no attribute
'_default_manager'
}}}
The same happens when making a new migration using `makemigrations`, and
when migrating an app that doesn't contain the swappable model.
--
Ticket URL: <https://code.djangoproject.com/ticket/24291>
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