Fixes #42. Putting a taggable manager on an abstract model now works.

taggit/managers.py

@@ -65,7 +65,7 @@ class TaggableManager(RelatedField):
         self.model = cls
         cls._meta.add_field(self)
         setattr(cls, name, self)
-        if self.use_gfk:
+        if self.use_gfk and not cls._meta.abstract:
             tagged_items = GenericRelation(self.through)
             tagged_items.contribute_to_class(cls, "tagged_items")
 

taggit/tests/models.py

@@ -103,3 +103,15 @@ class OfficialPet(models.Model):
 class OfficialHousePet(OfficialPet):
     trained = models.BooleanField()
 
+
+class Media(models.Model):
+    tags = TaggableManager()
+    
+    class Meta:
+        abstract = True
+
+class Photo(Media):
+    pass
+
+class Movie(Media):
+    pass

taggit/tests/tests.py

@@ -8,7 +8,7 @@ from taggit.tests.forms import (FoodForm, DirectFoodForm, CustomPKFoodForm,
 from taggit.tests.models import (Food, Pet, HousePet, DirectFood, DirectPet,
     DirectHousePet, TaggedPet, CustomPKFood, CustomPKPet, CustomPKHousePet,
     TaggedCustomPKPet, OfficialFood, OfficialPet, OfficialHousePet,
-    OfficialThroughModel, OfficialTag)
+    OfficialThroughModel, OfficialTag, Photo, Movie)
 from taggit.utils import parse_tags, edit_string_for_tags
 
 
@@ -212,6 +212,21 @@ class TaggableManagerTestCase(BaseTaggingTestCase):
             unicode(self.taggeditem_model.objects.all()[0]),
             "ross tagged with president"
         )
+    
+    def test_abstract_subclasses(self):
+        p = Photo.objects.create()
+        p.tags.add("outdoors", "pretty")
+        self.assert_tags_equal(
+            p.tags.all(),
+            ["outdoors", "pretty"]
+        )
+        
+        m = Movie.objects.create()
+        m.tags.add("hd")
+        self.assert_tags_equal(
+            m.tags.all(),
+            ["hd"],
+        )
 
 
 class TaggableManagerDirectTestCase(TaggableManagerTestCase):