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
29123	Changing an IntegerField to a ForeignKey generates incorrectly ordered migration operations if the field is in unique_together	Ed Morley		"Replacing an integer field with a foreign key of the same name, results in an `OperationalError` when creating/applying the migration. 

This affects Django master + v1.11.10, and both the SQLite and MySQL backends (others not tested).

== STR:
1. Git clone [https://github.com/edmorley/django-migration-int-to-fk-testcase https://github.com/edmorley/django-migration-int-to-fk-testcase]
2. `pip install https://github.com/django/django/archive/master.zip`
3. `./manage.py migrate`
4. `cp testapp/models_new.py testapp/models.py`
5. `./manage.py makemigrations --name broken_migration`
6. `./manage.py migrate`

== Expected:

New migration is created/applied successfully, which converts from the [https://github.com/edmorley/django-migration-int-to-fk-testcase/blob/master/testapp/models.py original model] to the [https://github.com/edmorley/django-migration-int-to-fk-testcase/blob/master/testapp/models_new.py new model].

== Actual:

The new `0002_broken_migration.py` migration incorrectly lists the `AddField` operation before the `RemoveField` operation...

{{{#!python
    operations = [
        migrations.AddField(
            model_name='bar',
            name='foo',
            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='testapp.Foo'),
        ),
        migrations.RemoveField(
            model_name='bar',
            name='foo_id',
        ),
        migrations.AlterUniqueTogether(
            name='bar',
            unique_together={('name', 'foo')},
        ),
    ]
}}}

Which results in an exception at step 6...

{{{#!bash
$ ./manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions, testapp
Running migrations:
  Applying testapp.0002_broken_migration...Traceback (most recent call last):
  File "".../site-packages/django/db/backends/utils.py"", line 83, in _execute
    return self.cursor.execute(sql)
  File "".../site-packages/django/db/backends/sqlite3/base.py"", line 290, in execute
    return Database.Cursor.execute(self, query)
sqlite3.OperationalError: duplicate column name: foo_id
}}}

== Additional notes:
* Without the `unique_together` on model `Bar`, the bug does not occur.
* This affects both the SQLite backend and the MySQL backend (others not tested).
* At time of testing, django master was at revision `6d794fb76212bb8a62fe2cd97cff173054e1c626`.
* The above was using Python 3.6.2."	Bug	closed	Migrations	dev	Normal	duplicate			Accepted	0	0	0	0	0	0