id summary reporter owner description type status component version severity resolution keywords cc stage has_patch needs_docs needs_tests needs_better_patch easy ui_ux 24225 KeyError when migrating in 1.8a1/master@728b6fd (does not occur in 1.7.3) Henrik Heimbuerger nobody "When running the `migrate` management command (even if there is nothing to migrate) on 1.8a1 or the current GitHub master, I'm getting the following uncaught `KeyError`: {{{ Running migrations: Rendering model states... DONE Traceback (most recent call last): File ""manage.py"", line 10, in execute_from_command_line(sys.argv) File ""d:\develop\myproj\django-trunk\django\core\management\__init__.py"", line 330, in execute_from_command_line utility.execute() File ""d:\develop\myproj\django-trunk\django\core\management\__init__.py"", line 322, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File ""d:\develop\myproj\django-trunk\django\core\management\base.py"", line 350, in run_from_argv self.execute(*args, **cmd_options) File ""d:\develop\myproj\django-trunk\django\core\management\base.py"", line 401, in execute output = self.handle(*args, **options) File ""d:\develop\myproj\django-trunk\django\core\management\commands\migrate.py"", line 187, in handle executor.migrate(targets, plan, fake=options.get(""fake"", False)) File ""d:\develop\myproj\django-trunk\django\db\migrations\executor.py"", line 89, in migrate state = migration.mutate_state(state) # state is cloned inside File ""d:\develop\myproj\django-trunk\django\db\migrations\migration.py"", line 78, in mutate_state operation.state_forwards(self.app_label, new_state) File ""d:\develop\myproj\django-trunk\django\db\migrations\operations\fields.py"", line 50, in state_forwards state.reload_model(app_label, self.model_name_lower) File ""d:\develop\myproj\django-trunk\django\db\migrations\state.py"", line 61, in reload_model self._reload_one_model(rel_model._meta.app_label, rel_model._meta.model_name) File ""d:\develop\myproj\django-trunk\django\db\migrations\state.py"", line 68, in _reload_one_model self.models[app_label, model_name].render(self.apps) KeyError: ('myapp', 'somemodel') }}} The reported model is created and then only appears twice in my migrations: In `myapp/migrations/0001_initial.py`: {{{ migrations.AddField( model_name='somemodel', name='somefieldname', field=models.ForeignKey(to='myapp.AValidModel'), preserve_default=True, ), }}} and in `myapp/migrations/0002_a.py`: {{{ migrations.RemoveField( model_name='somemodel', name='somefieldname', ), }}} Other than that, the model hasn't been changed in the migrations. The application is closed source and I can't share real code with you unfortunately. I do have a debugger connected to the issue, but I have no idea where to even start debugging this. By checking the stack frame for `mutation.py:78` (`mutate_state()`), I can see that the ""current migration"" when this occurs is a `0002_b.py`, i.e. another migration dependent on `0001_initial.py` which therefore shouldn't be aware of the field removal yet. These migrations do work on 1.7.3. (But I can't really work on 1.7.3 because unit test startup takes minutes without `--keepdb`…) Whatever the cause of this is, I highly recommend catching `KeyError` in `_reload_one_model()` and rethrowing a proper exception with a descriptive error message, including the stage and specific migration at which this occurs. Because a `KeyError` being raised somewhere in the depths of the migration system tells me nothing about what or where the issue is." Bug new Migrations master Normal Unreviewed 0 0 0 0 0 0