Adding new custom permissions in Django

Question

I am using custom permissions in my Django models like this:

class T21Turma(models.Model):
    class Meta:
        permissions = (("can_view_boletim", "Can view boletim"),
                       ("can_view_mensalidades", "Can view mensalidades"),)

The problem is that when I add a permission to the list it doesn't get added to the auth_permission table when I run syncdb. What am I doing wrong. If it makes any difference I am using south for database migrations.

Adenoidectomy

You can fix the field length in the Permissions model: https://mcmap.net/q/219115/-django-fixture-fails-stating-quot-databaseerror-value-too-long-for-type-character-varying-50-quot – Aldrin

Answer 1

South does not track django.contrib.auth permissions. See ticket #211 for more information.

One of the comments on the ticket suggests that using the --all option on syncdb may solve the problem.

Terrorism

Sounds like exactly my problem except that I can't get the --all switch to work with syncdb nor do I find the switch documented anywhere. – Adenoidectomy

This worked after I upgraded to south 0.6.2 (I was running 0.5) previously. – Adenoidectomy

This just gives me the error "DatabaseError: value too long for type character varying(50)" – Pandowdy

that means you have a value already in the DB that is longer than 50 chars. – Dubose

@Pandowdy - I got that when my permission description was over 50 characters. Seems a likely place to make that mistake. – Concord

Answer 2

If you want "manage.py migrate" to do everything (without calling syncdb --all). You need to create new permissions with a migration:

user@host> manage.py datamigration myapp add_perm_foo --freeze=contenttypes --freeze=auth

Edit the created file:

class Migration(DataMigration):

    def forwards(self, orm):
        "Write your forwards methods here."
        ct, created = orm['contenttypes.ContentType'].objects.get_or_create(
            model='mymodel', app_label='myapp') # model must be lowercase!
        perm, created = orm['auth.permission'].objects.get_or_create(
            content_type=ct, codename='mymodel_foo', defaults=dict(name=u'Verbose Name'))

Jaws

there is no need for last three lines, defaults keyword argument of get_or_create can be used instead link – Crony

If you're using this method you need to add the options --freeze=contenttypes --freeze=auth to the datamigration command. Otherwise you'll get the error @Krilov mentions below. E.g: manage.py datamigration myapp add_perm_foo --freeze=contenttypes --freeze=auth – Tawnatawney

Answer 3

This worked for me:

./manage.py update_permissions

It is a django-extensions thing.

Glasscock

"DatabaseError: value too long for type character varying(50)". The cause is my permission's name was too long, but that's a horribly unhelpful error message, especially when I'm adding dozens of new permissions. – Pandowdy

Answer 4

You can connect to the post_migrate signal in order to update the permissions after migration. I use the following code, slightly modified from Dev with Passion and originally from django-extensions.

# Add to your project-level __init__.py

from south.signals import post_migrate

def update_permissions_after_migration(app,**kwargs):
    """
    Update app permission just after every migration.
    This is based on app django_extensions update_permissions management command.
    """
    from django.conf import settings
    from django.db.models import get_app, get_models
    from django.contrib.auth.management import create_permissions

    create_permissions(get_app(app), get_models(), 2 if settings.DEBUG else 0)

post_migrate.connect(update_permissions_after_migration)

Period

This has an issue when working with something like gunicorn to run the app, namely it fails at finding environmental variable that is set in the wsgi.py file. – Wilona

Answer 5

When i runnning migration with following code

ct, created = orm['contenttypes.ContentType'].objects.get_or_create(model='mymodel',     app_label='myapp') # model must bei lowercase!
perm, created = orm['auth.permission'].objects.get_or_create(content_type=ct, codename='mymodel_foo')

I getting folloving error

File "C:\Python26\lib\site-packages\south-0.7.3-py2.6.egg\south\orm.py", line 170, in  __getitem__
raise KeyError("The model '%s' from the app '%s' is not available in this migration." % (model, app))
KeyError: "The model 'contenttype' from the app 'contenttypes' is not available in this migration."

To prevent this error, i modified the code

from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.models import Permission

class Migration(DataMigration):

    def forwards(self, orm):
        "Write your forwards methods here."
        ct = ContentType.objects.get(model='mymodel', app_label='myapp') 
        perm, created = Permission.objects.get_or_create(content_type=ct, codename='mymodel_foo')
        if created:
            perm.name=u'my permission description'
            perm.save()

Krilov

Bad idea; you should use the frozen ORM. Add --freeze=contenttypes --freeze=auth to your ./manage.py datamigration command line. – Period