#23916: makemigrations does not detect/like model name case changes
----------------------------+--------------------
Reporter: scoenye | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.7
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
Starting with
{{{
class Evidence(models.Model):
rubrictype = models.ForeignKey('Rubrictype')
class Rubrictype(models.Model):
type_code = models.CharField(max_length=1)
}}}
Make the initial migration:
{{{
$ ./manage.py makemigrations
Migrations for 'as_migrations':
0001_initial.py:
- Create model Evidence
- Create model Rubrictype
- Add field rubrictype to evidence
}}}
Change the name of Rubrictype to RubricType:
{{{
class Evidence(models.Model):
rubrictype = models.ForeignKey('RubricType')
class RubricType(models.Model):
type_code = models.CharField(max_length=1)
}}}
Generate the migration:
{{{
$ ./manage.py makemigrations
Migrations for 'as_migrations':
0002_auto_20141125_1930.py:
- Alter field rubrictype on evidence
}}}
Django does not detect the name change on the RubricType model itself. No
confirmation is requested for the name change and no operation is
generated. The problem is that any subsequent makemigrations run will
generate the same operation ad infinitum:
{{{
$ ./manage.py makemigrations
Migrations for 'as_migrations':
0003_auto_20141125_1930.py:
- Alter field rubrictype on evidence
}}}
If instead the name is changed to RubricXype:
{{{
class Evidence(models.Model):
rubrictype = models.ForeignKey('RubricXype')
class RubricXype(models.Model):
type_code = models.CharField(max_length=1)
}}}
the corresponding migration becomes
{{{
$ ./manage.py makemigrations
Did you rename the as_migrations.Rubrictype model to RubricXype? [y/N] y
Migrations for 'as_migrations':
0002_auto_20141125_1956.py:
- Rename model Rubrictype to RubricXype
}}}
This migration generates a RenameModel operation only and any subsequent
makemigrations runs will properly report "No changes detected". So it
appears the change detector does not pick up on capitalization changes in
model names.
Trying to work around by adding a
{{{
migrations.RenameModel(
old_name='Rubrictype',
new_name='RubricType',
)
}}}
to the auto generated operations results in a ValueError exception when
makemigrations is run again:
{{{
$ ./manage.py makemigrations
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/core/management/__init__.py", line 385, in
execute_from_command_line
utility.execute()
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/core/management/base.py", line 338, in execute
output = self.handle(*args, **options)
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/core/management/commands/makemigrations.py", line 111, in
handle
convert_apps=app_labels or None,
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/db/migrations/autodetector.py", line 42, in changes
changes = self._detect_changes(convert_apps, graph)
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/db/migrations/autodetector.py", line 109, in
_detect_changes
self.old_apps = self.from_state.render(ignore_swappable=True)
File "/home/svencoenye/developer/django_test/lib/python2.7/site-
packages/django/db/migrations/state.py", line 89, in render
model=lookup_model,
ValueError: Lookup failed for model referenced by field
as_migrations.Evidence.rubrictype: as_migrations.RubricType
}}}
The sequence of the operations does not matter. Neither does substituting
the RenameModel operation for the AlterField operation.
(Looking at the next to last entry in the traceback, the autodetector
seems to be looking for the new name in the old_apps state?)
It is possible, however, to go the long way around and use two separate
migrations: Rubrictype -> RubricXype. RubricXype -> RubricType works
without getting the migration state stuck and does not throw an exception.
--
Ticket URL: <https://code.djangoproject.com/ticket/23916>
Django <https://code.djangoproject.com/>
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