Raise ValueError with invalid types in `add`

taggit/managers.py

@@ -133,12 +133,17 @@ class _TaggableManager(models.Manager):
 
     @require_instance_manager
     def add(self, *tags):
-        str_tags = set([
-            t
-            for t in tags
-            if not isinstance(t, self.through.tag_model())
-        ])
-        tag_objs = set(tags) - str_tags
+        str_tags = set()
+        tag_objs = set()
+        for t in tags:
+            if isinstance(t, self.through.tag_model()):
+                tag_objs.add(t)
+            elif isinstance(t, six.string_types):
+                str_tags.add(t)
+            else:
+                raise ValueError("Cannot add {0} ({1}). Expected {2} or str.".format(
+                    t, type(t), type(self.through.tag_model())))
+
         # If str_tags has 0 elements Django actually optimizes that to not do a
         # query.  Malcolm is very smart.
         existing = self.through.tag_model().objects.filter(

tests/tests.py

@@ -86,6 +86,14 @@ class TagModelTestCase(BaseTaggingTransactionTestCase):
             "category-awesome-1"
         ], attr="slug")
 
+    def test_integers(self):
+        """Adding an integer as a tag should raise a ValueError (#237)."""
+        apple = self.food_model.objects.create(name="apple")
+        with self.assertRaisesRegexp(ValueError, (
+                r"Cannot add 1 \(<(type|class) 'int'>\). "
+                r"Expected <class 'django.db.models.base.ModelBase'> or str.")):
+            apple.tags.add(1)
+
 class TagModelDirectTestCase(TagModelTestCase):
     food_model = DirectFood
     tag_model = Tag