#29124: Generated migration orders RemoveField and AlterUniqueTogether
incorrectly,
causing FieldDoesNotExist
--------------------------------------+------------------------
Reporter: Ed Morley | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
--------------------------------------+------------------------
Removing a field and its corresponding `unique_together` entry results in
a `FieldDoesNotExist` exception when creating/applying the migration.
This affects Django master + v1.11.10, and both the SQLite and MySQL
backends (others not tested).
(See also #29123 which also only reproduces when `unique_together` is
used)
== STR:
1. Git clone [https://github.com/edmorley/django-migration-remove-field-
testcase https://github.com/edmorley/django-migration-remove-field-
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-remove-field-
testcase/blob/master/testapp/models.py original model] to the
[https://github.com/edmorley/django-migration-remove-field-
testcase/blob/master/testapp/models_new.py new model].
== Actual:
The new `0002_broken_migration.py` migration incorrectly lists the
`RemoveField` operation before the `AlterUniqueTogether` operation...
{{{#!python
operations = [
migrations.RemoveField(
model_name='push',
name='foo',
),
migrations.AlterUniqueTogether(
name='push',
unique_together={('repository', 'revision')},
),
]
}}}
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/models/options.py", line 564, in
get_field
return self.fields_map[field_name]
KeyError: 'foo'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
...
File ".../site-packages/django/db/backends/base/schema.py", line 286, in
create_model
columns = [model._meta.get_field(field).column for field in fields]
File ".../site-packages/django/db/backends/base/schema.py", line 286, in
<listcomp>
columns = [model._meta.get_field(field).column for field in fields]
File ".../site-packages/django/db/models/options.py", line 566, in
get_field
raise FieldDoesNotExist("%s has no field named '%s'" %
(self.object_name, field_name))
django.core.exceptions.FieldDoesNotExist: Push has no field named 'foo'
}}}
== Additional notes:
* If the `('repository', 'revision')` entry in `unique_together` is
omitted from both the original and new models, then 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.
--
Ticket URL: <https://code.djangoproject.com/ticket/29124>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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