[Django] #25551: makemigrations when adding a ForeignKey to a newly created model along with a unique_together constraint must create fields before the unique_together constraint

[Django]

#25551: makemigrations when adding a ForeignKey to a newly created model along 
with
a unique_together constraint must create fields before the unique_together
constraint
----------------------------+--------------------
     Reporter:  mssnlayam   |      Owner:  nobody
         Type:  Bug         |     Status:  new
    Component:  Migrations  |    Version:  1.8
     Severity:  Normal      |   Keywords:
 Triage Stage:  Unreviewed  |  Has patch:  0
Easy pickings:  0           |      UI/UX:  0
----------------------------+--------------------
 When adding a new model and a `ForeignKey` to it as well a
 `unique_together` constraint for the `ForeignKey` field, Django migrations
 should create the field before applying the `unique_together` constraint.

 In the example below, I am adding a new `Author` model, a field to this
 model and a `unique_together` constraint for this field.

 {{{#!diff
  from django.db import models

 +class Author(models.Model):
 +    name = models.CharField(max_length=255)
 +
  class Book(models.Model):
      name = models.CharField(max_length=255)
 +    author = models.ForeignKey(Author, null=True)
 +    class Meta:
 +        unique_together = (
 +            ('name', 'author'),
 +        )
 }}}

 Django's migrations framework produces the following summary output:

 {{{
 Migrations for 'testapp':
   0002_auto_20151013_1354.py:
     - Create model Author
     - Alter unique_together for book (1 constraint(s))
     - Add field author to book
 }}}

 Here's the relevant portion of the migrations file:

 {{{#!python
     operations = [
         migrations.CreateModel(
             name='Author',
             fields=[
                 ('id', models.AutoField(verbose_name='ID',
 serialize=False, auto_created=True, primary_key=True)),
                 ('name', models.CharField(max_length=255)),
             ],
         ),
         migrations.AlterUniqueTogether(
             name='book',
             unique_together=set([('name', 'author')]),
         ),
         migrations.AddField(
             model_name='book',
             name='author',
             field=models.ForeignKey(to='testapp.Author', null=True),
         ),
     ]
 }}}

 This migration fails with the following stacktrace:
 {{{
 Operations to perform:
   Apply all migrations: testapp
 Running migrations:
   Rendering model states... DONE
   Applying testapp.0002_auto_20151013_1354...Traceback (most recent call
 last):
   File "./manage.py", line 10, in <module>
     execute_from_command_line(sys.argv)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/core/management/__init__.py", line 351, in
 execute_from_command_line
     utility.execute()
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/core/management/__init__.py", line 343, in execute
     self.fetch_command(subcommand).run_from_argv(self.argv)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/core/management/base.py", line 394, in run_from_argv
     self.execute(*args, **cmd_options)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/core/management/base.py", line 445, in execute
     output = self.handle(*args, **options)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/core/management/commands/migrate.py", line 222, in handle
     executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/migrations/executor.py", line 110, in migrate
     self.apply_migration(states[migration], migration, fake=fake,
 fake_initial=fake_initial)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/migrations/executor.py", line 148, in apply_migration
     state = migration.apply(state, schema_editor)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/migrations/migration.py", line 115, in apply
     operation.database_forwards(self.app_label, schema_editor, old_state,
 project_state)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/migrations/operations/models.py", line 359, in
 database_forwards
     getattr(new_model._meta, self.option_name, set()),
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/backends/sqlite3/schema.py", line 219, in
 alter_unique_together
     self._remake_table(model, override_uniques=new_unique_together)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/backends/sqlite3/schema.py", line 140, in _remake_table
     self.create_model(temp_model)
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/backends/base/schema.py", line 272, in create_model
     columns = [model._meta.get_field(field).column for field in fields]
   File "/home/vagrant/testunique-env/local/lib/python2.7/site-
 packages/django/db/models/options.py", line 554, in get_field
     raise FieldDoesNotExist('%s has no field named %r' %
 (self.object_name, field_name))
 django.core.exceptions.FieldDoesNotExist: Book has no field named
 u'author'
 }}}

--
Ticket URL: <https://code.djangoproject.com/ticket/25551>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/052.f884231f4c0f9dd1a456178433fe3b5c%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.