Fixed #15915 -- Cleaned handling of duplicate permission codenames

Previously, a duplicate model, codename for permission would lead to
database integrity error. Cleaned the implementation so that this case
now raises an CommandError instead.

django/contrib/auth/management/__init__.py

@@ -9,6 +9,7 @@ import unicodedata
 
 from django.contrib.auth import models as auth_app, get_user_model
 from django.core import exceptions
+from django.core.management.base import CommandError
 from django.db.models import get_models, signals
 from django.utils import six
 from django.utils.six.moves import input
@@ -18,13 +19,43 @@ def _get_permission_codename(action, opts):
     return '%s_%s' % (action, opts.object_name.lower())
 
 
-def _get_all_permissions(opts):
+def _get_all_permissions(opts, ctype):
-    "Returns (codename, name) for all permissions in the given opts."
+    """
+    Returns (codename, name) for all permissions in the given opts.
+    """
+    builtin = _get_builtin_permissions(opts)
+    custom = list(opts.permissions)
+    _check_permission_clashing(custom, builtin, ctype)
+    return builtin + custom
+
+def _get_builtin_permissions(opts):
+    """
+    Returns (codename, name) for all autogenerated permissions.
+    """
     perms = []
     for action in ('add', 'change', 'delete'):
-        perms.append((_get_permission_codename(action, opts), 'Can %s %s' % (action, opts.verbose_name_raw)))
+        perms.append((_get_permission_codename(action, opts),
-    return perms + list(opts.permissions)
+            'Can %s %s' % (action, opts.verbose_name_raw)))
+    return perms
 
+def _check_permission_clashing(custom, builtin, ctype):
+    """
+    Check that permissions for a model do not clash. Raises CommandError if
+    there are duplicate permissions.
+    """
+    pool = set()
+    builtin_codenames = set(p[0] for p in builtin)
+    for codename, _name in custom:
+        if codename in pool:
+            raise CommandError(
+                "The permission codename '%s' is duplicated for model '%s.%s'." %
+                (codename, ctype.app_label, ctype.model_class().__name__))
+        elif codename in builtin_codenames:
+            raise CommandError(
+                "The permission codename '%s' clashes with a builtin permission "
+                "for model '%s.%s'." %
+                (codename, ctype.app_label, ctype.model_class().__name__))
+        pool.add(codename)
 
 def create_permissions(app, created_models, verbosity, **kwargs):
     from django.contrib.contenttypes.models import ContentType
@@ -39,7 +70,7 @@ def create_permissions(app, created_models, verbosity, **kwargs):
     for klass in app_models:
         ctype = ContentType.objects.get_for_model(klass)
         ctypes.add(ctype)
-        for perm in _get_all_permissions(klass._meta):
+        for perm in _get_all_permissions(klass._meta, ctype):
             searched_perms.append((ctype, perm))
 
     # Find all the Permissions that have a context_type for a model we're

django/contrib/auth/tests/management.py

@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 from datetime import date
 
 from django.contrib.auth import models, management
+from django.contrib.auth.management import create_permissions
 from django.contrib.auth.management.commands import changepassword
 from django.contrib.auth.models import User
 from django.contrib.auth.tests import CustomUser
@@ -167,3 +168,43 @@ class CreatesuperuserManagementCommandTestCase(TestCase):
             )
 
         self.assertEqual(CustomUser.objects.count(), 0)
+
+
+class PermissionDuplicationTestCase(TestCase):
+
+    def setUp(self):
+        self._original_user_permission = models.User._meta.permissions
+
+    def tearUp(self):
+        models.User._meta.permissions = self._original_user_permissions
+
+    def test_duplicated_permissions(self):
+        """
+        Test that we show proper error message if we are trying to create
+        duplicate permissions.
+        """
+        # check duplicated default permission
+        models.Permission._meta.permissions = [
+           ('change_permission', 'Can edit permission (duplicate)')]
+        self.assertRaisesRegexp(CommandError,
+            "The permission codename 'change_permission' clashes with a "
+            "builtin permission for model 'auth.Permission'.",
+            create_permissions, models, [], verbosity=0)
+
+        # check duplicated custom permissions
+        models.Permission._meta.permissions = [
+            ('my_custom_permission', 'Some permission'),
+            ('other_one', 'Some other permission'),
+            ('my_custom_permission', 'Some permission with duplicate permission code'),
+        ]
+        self.assertRaisesRegexp(CommandError,
+            "The permission codename 'my_custom_permission' is duplicated for model "
+            "'auth.Permission'.",
+            create_permissions, models, [], verbosity=0)
+
+        # should not raise anything
+        models.Permission._meta.permissions = [
+            ('my_custom_permission', 'Some permission'),
+            ('other_one', 'Some other permission'),
+        ]
+        create_permissions(models, [], verbosity=0)