Adding django admin permissions in a migration: Permission matching query does not exist - django

Question

I wanted to add some groups and assign permissions to them in a manually written migration but if I run it on a clean DB it creates permissions only after running all migrations.
I've found this ticket: https://code.djangoproject.com/ticket/23422
but I cannot comment there (it's possible I was banned after expressing some discontent with GeoDjango docs), so I'll share an improvement over the solution there below.

Answer 1

In django 1.10 the following code could be used:
from django.contrib.auth.management import create_permissions
def migrate_permissions(apps, schema_editor):
for app_config in apps.get_app_configs():
app_config.models_module = True
create_permissions(app_config, apps=apps, verbosity=0)
app_config.models_module = None

Answer 2

Django <= 1.9
see another answer for Django 1.10+
It's enough to call create_permissions:
from django.contrib.auth.management import create_permissions
apps.models_module = True
create_permissions(apps, verbosity=0)
apps.models_module = None
The whole migration being something like this
# coding:utf-8
from django.db import migrations
from django.contrib.auth.models import Permission, Group
from django.contrib.auth.management import create_permissions
from django.contrib.contenttypes.models import ContentType
from django.conf import settings
MODERATORS_PERMISSIONS = ['change_modelname', ]
def add_permissions(apps, schema_editor):
apps.models_module = True
create_permissions(apps, verbosity=0)
apps.models_module = None
moderators_group = Group.objects.get_or_create(
name=settings.MODERATORS_GROUP)[0]
for codename in MODERATORS_PERMISSIONS:
permission = Permission.objects.get(codename=codename)
moderators_group.permissions.add(permission)
class Migration(migrations.Migration):
dependencies = [
('contenttypes', '0002_remove_content_type_name'),
('thisappname', '0001_initial'),
]
operations = [
migrations.RunPython(add_permissions),
]

Answer 3

And if you want something that will work on any version (or that will keep working when you upgrade):
from django.contrib.auth.management import create_permissions
version = django.VERSION
if version[0] >= 1 and django.VERSION[1] > 9:
for app_config in apps.get_app_configs():
app_config.models_module = True
create_permissions(app_config, apps=apps, verbosity=0)
app_config.models_module = None
else:
apps.models_module = True
create_permissions(apps, verbosity=0)
apps.models_module = None

Answer 4

Trying to get an permission during migrations causes an exception(Permission matching query does not exist) in Django. It's an old problem in Django.
In 1.6 version I solved it via #int_ua's snippet but in 1.11 version it doesn't work(I'm not sure why).
I used this workaround in 1.11 version:
def _assign_group_permissions(permission_codenames, apps, group_name):
permission_list = []
Permission = apps.get_model('auth', 'Permission')
for permission_codename in permission_codenames:
for permission in Permission.objects.all():
if permission.codename == permission_codename:
permission_list.append(permission)
Group = apps.get_model('auth', 'Group')
group = Group.objects.get(name=group_name)
group.permissions.add(*permission_list)
Instead of Permission.objects.get(codename='your_code_name') it's possible to iterate over all permissions and choose suitable one by codename.

Answer 5

Django 3.2
Here is a version for Django 3.2, which you can run from the command line:
./manage.py fix_permissions
# app_label/management/commands/fix_permissions.py
from django.contrib.auth.models import Permission
from django.contrib.auth.management import create_permissions
from django.core.management.base import BaseCommand
from django.apps import apps
class Command(BaseCommand):
help = 'Recreate permissions from scratch'
def handle(self, *args, **options):
# Run this method via shell whenever any amendments in any of the tables is made
print("Deleting existing user permissions...")
Permission.objects.all().delete()
for app_config in apps.get_app_configs():
print(f"Adding user permissions for {app_config}...")
app_config.models_module = True
create_permissions(app_config, apps=apps, verbosity=0)
app_config.models_module = None
print("DONE.")