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
22581	Field.get_default() causes migration to fail if non-string value returned	martin.tirsel@…	Andrew Godwin	"If get_default() method on a custom field returns for example a dictionary instance, then the migration fails. Here is an example of such implementation (djano-jsonfield):

https://bitbucket.org/schinckel/django-jsonfield/src/28c51eb06a65c1e7b5d8022031aebb034e0c129c/jsonfield/fields.py?at=default#cl-58

I created a custom user, where I wanted to add:

{{{
#!python
class User(AbstractBaseUser, PermissionsMixin):
    # ...
    data = JSONField(default='{}')
    # ...
}}}

{{{
$ ./manage.py makemigrations
Migrations for 'account':
  0002_user_data.py:
    - Add field data to user
$ ./manage.py migrate
Operations to perform:
  Synchronize unmigrated apps: admin, contenttypes, auth, sessions
  Apply all migrations: account
Synchronizing apps without migrations:
  Creating tables...
  Installing custom SQL...
  Installing indexes...
Running migrations:
  Applying account.0002_user_data...Traceback (most recent call last):
  File ""./manage.py"", line 10, in <module>
    execute_from_command_line(sys.argv)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 427, in execute_from_command_line
    utility.execute()
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 419, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/core/management/base.py"", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/core/management/base.py"", line 337, in execute
    output = self.handle(*args, **options)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py"", line 146, in handle
    executor.migrate(targets, plan, fake=options.get(""fake"", False))
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 60, in migrate
    self.apply_migration(migration, fake=fake)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 94, in apply_migration
    migration.apply(project_state, schema_editor)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/migrations/migration.py"", line 97, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py"", line 36, in database_forwards
    field,
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/backends/schema.py"", line 395, in add_field
    self.execute(sql, params)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/backends/schema.py"", line 98, in execute
    cursor.execute(sql, params)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 81, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 65, in execute
    return self.cursor.execute(sql, params)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/utils.py"", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File ""/home/bruce/.virtualenv/paddle/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: can't adapt type 'dict'
}}}

Variables state:

{{{
params: [{}]
sql: u'ALTER TABLE ""account_user"" ADD COLUMN ""data"" text DEFAULT %s NOT NULL'
}}}


I pip installed Django from stable/1.7.x branch and using psycopg2==2.5.2 The get_default() method can return anything (as described here - https://code.djangoproject.com/ticket/8633#comment:2), so Django should handle handle such cases somehow."	Bug	closed	Migrations	dev	Release blocker	fixed	migration	loic84 and	Accepted	0	0	0	0	0	0