changing a ForeignKey to CharField breaks migrations

[django@…]

See my example project at:

​https://github.com/pjrobertson/django_migrations_bug

Basically, I'd decided that instead of using another model to represent a specific field on my 'parent' model, I'd just use a plain old charfield.

Check out my repo, and run ./manage.py migrate migr and you'll see the problem. For reference, the full trace is here:

  Applying migr.0002_auto_20140806_1432...Traceback (most recent call last):
  File "./manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/core/management/base.py", line 337, in execute
    output = self.handle(*args, **options)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 160, in handle
    executor.migrate(targets, plan, fake=options.get("fake", False))
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/db/migrations/executor.py", line 63, in migrate
    self.apply_migration(migration, fake=fake)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/db/migrations/executor.py", line 97, in apply_migration
    migration.apply(project_state, schema_editor)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/db/migrations/migration.py", line 107, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File "/Users/patrick/.virtualenvs/migr/lib/python2.7/site-packages/django/db/migrations/operations/fields.py", line 129, in database_forwards
    elif isinstance(to_field.rel.to, six.string_types):
AttributeError: 'NoneType' object has no attribute 'to'

In order to get the example project into its current state I did the following:

$ django-admin.py startproject migr
$ # add 'migr' to INSTALLED_APPS
$ # created models.py with the 'BEFORE' (see commented code in models.py) code
$ ./manage.py makemigrations migr
$ ./manage.py migrate
$ # updated models.py to how it is in the repo (a char field for 'phone_number')
$ ./manage.py makemigrations migr
$ ./manage.py migrate
$ # EXCEPTION

[django@…]

My workaround was to rename the field to something temporary like phone_number_temp, then create a migration, rename it back to phone_number and create another migration.

Perhaps that's what makemigrations should do automatically

[Andrew Godwin <andrew@…>]

In dfe86449c9951824dfa95d44af36ef1d8e578bdc:

Fixed #23244: Error altering FK to non-FK in migrations

[Andrew Godwin <andrew@…>]

In 0e69af51b1557ebe3ce93fe31498f3fa797b4b83:

[1.7.x] Fixed #23244: Error altering FK to non-FK in migrations

[django@…]

That was quick. Cheers Andrew :)