#25247: makemigrations unable to generate necessary migration for making a
superclass abstract
-------------------------------+-------------------------------------
Reporter: rapilabs | Owner: nobody
Type: Uncategorized | Status: new
Component: Migrations | Version: 1.8
Severity: Normal | Keywords: abstract makemigrations
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------+-------------------------------------
If a user has an existing model state that uses model inheritance and
changes a superclass to become abstract then makemigrations is unable to
produce a suitable migration. In fact the resulting migration will
actually raise an exception when run.
This is non-trivial as a generated migration may require some data
migration operations.
This was reported by a user on #django and I was able to reproduce with a
small test:
{{{#!python
# Initial model state:
class Foo(models.Model):
name = models.CharField(max_length=255)
class Bar(Foo):
pass
# Subsequent model state:
class Foo(models.Model):
name = models.CharField(max_length=255)
class Meta:
abstract=True
class Bar(Foo):
pass
# running makemigrations results in:
class Migration(migrations.Migration):
dependencies = [
('foobar', '0001_initial'),
]
operations = [
migrations.RemoveField(
model_name='bar',
name='foo_ptr',
),
migrations.AddField(
model_name='bar',
name='id',
field=models.AutoField(auto_created=True, primary_key=True,
default=1, serialize=False, verbose_name='ID'),
preserve_default=False,
),
migrations.AddField(
model_name='bar',
name='name',
field=models.CharField(default='asdf', max_length=255),
preserve_default=False,
),
migrations.DeleteModel(
name='Foo',
),
]
# which results in the following when attempting to run migrate:
(env)dsanders ~/test/abstract_update/test_abstract $ ./manage.py migrate
Operations to perform:
Synchronize unmigrated apps: staticfiles, messages
Apply all migrations: admin, foobar, contenttypes, auth, sessions
Synchronizing apps without migrations:
Creating tables...
Running deferred SQL...
Installing custom SQL...
Running migrations:
Rendering model states...Traceback (most recent call last):
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/core/management/__init__.py", line 338, in
execute_from_command_line
utility.execute()
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/core/management/__init__.py", line 330, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/core/management/base.py", line 393, in run_from_argv
self.execute(*args, **cmd_options)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/core/management/base.py", line 444, in execute
output = self.handle(*args, **options)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/core/management/commands/migrate.py", line 221, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/migrations/executor.py", line 104, in migrate
state = migration.mutate_state(state, preserve=do_run)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/migrations/migration.py", line 83, in mutate_state
operation.state_forwards(self.app_label, new_state)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/migrations/operations/fields.py", line 51, in
state_forwards
state.reload_model(app_label, self.model_name_lower)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/migrations/state.py", line 152, in reload_model
self.apps.render_multiple(states_to_be_rendered)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/migrations/state.py", line 262, in render_multiple
model.render(self)
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/migrations/state.py", line 546, in render
body,
File "/Users/dsanders/test/abstract_update/env/lib/python2.7/site-
packages/django/db/models/base.py", line 254, in __new__
'base class %r' % (field.name, name, base.__name__)
django.core.exceptions.FieldError: Local field u'id' in class 'Bar'
clashes with field of similar name from base class 'Foo'
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25247>
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