Add helper function for django-guardian.

polymorphic/contrib/guardian.py

@@ -0,0 +1,35 @@
+from django.contrib.contenttypes.models import ContentType
+
+
+def get_polymorphic_base_content_type(obj):
+    """
+    Helper function to return the base polymorphic content type id. This should used with django-guardian and the
+    GUARDIAN_GET_CONTENT_TYPE option.
+
+    See the django-guardian documentation for more information:
+
+    https://django-guardian.readthedocs.io/en/latest/configuration.html#guardian-get-content-type
+    """
+    if hasattr(obj, 'polymorphic_model_marker'):
+        try:
+            superclasses = list(obj.__class__.mro())
+        except TypeError:
+            # obj is an object so mro() need to be called with the obj.
+            superclasses = list(obj.__class__.mro(obj))
+
+        polymorphic_superclasses = list()
+        for sclass in superclasses:
+            if hasattr(sclass, 'polymorphic_model_marker'):
+                polymorphic_superclasses.append(sclass)
+
+        # PolymorphicMPTT adds an additional class between polymorphic and base class.
+        if hasattr(obj, 'can_have_children'):
+            root_polymorphic_class = polymorphic_superclasses[-3]
+        else:
+            root_polymorphic_class = polymorphic_superclasses[-2]
+        ctype = ContentType.objects.get_for_model(root_polymorphic_class)
+
+    else:
+        ctype = ContentType.objects.get_for_model(obj)
+
+    return ctype

polymorphic/tests.py

@@ -21,6 +21,7 @@ from django.db import models
 from django.contrib.contenttypes.models import ContentType
 from django.utils import six
 
+from polymorphic.contrib.guardian import get_polymorphic_base_content_type
 from polymorphic.models import PolymorphicModel
 from polymorphic.managers import PolymorphicManager
 from polymorphic.query import PolymorphicQuerySet
@@ -195,6 +196,7 @@ class ModelWithMyManagerNoDefault(ShowFieldTypeAndContent, Model2A):
     my_objects = MyManager()
     field4 = models.CharField(max_length=10)
 
+
 class ModelWithMyManagerDefault(ShowFieldTypeAndContent, Model2A):
     my_objects = MyManager()
     objects = PolymorphicManager()
@@ -1189,6 +1191,24 @@ class PolymorphicTests(TestCase):
         result = Model2B.objects.annotate(val=Concat('field1', 'field2'))
         self.assertEqual(list(result), [])
 
+    def test_contrib_guardian(self):
+        # Regular Django inheritance should return the child model content type.
+        obj = PlainC()
+        ctype = get_polymorphic_base_content_type(obj)
+        self.assertEqual(ctype.name, 'plain c')
+
+        ctype = get_polymorphic_base_content_type(PlainC)
+        self.assertEqual(ctype.name, 'plain c')
+
+        # Polymorphic inheritance should return the parent model content type.
+        obj = Model2D()
+        ctype = get_polymorphic_base_content_type(obj)
+        self.assertEqual(ctype.name, 'model2a')
+
+        ctype = get_polymorphic_base_content_type(Model2D)
+        self.assertEqual(ctype.name, 'model2a')
+
+
 class RegressionTests(TestCase):
 
     def test_for_query_result_incomplete_with_inheritance(self):
@@ -1210,6 +1230,7 @@ class RegressionTests(TestCase):
         expected_queryset = [bottom]
         self.assertQuerysetEqual(Bottom.objects.all(), [repr(r) for r in expected_queryset])
 
+
 class MultipleDatabasesTests(TestCase):
     multi_db = True