Fixed #95 -- don't stomp over attributes/fields of a model in tagging…

….register

tagging/__init__.py

@@ -1,30 +1,50 @@
-from django.utils.translation import ugettext as _
-
 from tagging.managers import ModelTaggedItemManager, TagDescriptor
 
+
+
 VERSION = (0, 4, 'pre')
 
+
+
 class AlreadyRegistered(Exception):
     """
     An attempt was made to register a model more than once.
     """
     pass
 
+
 registry = []
 
+
 def register(model, tag_descriptor_attr='tags',
              tagged_item_manager_attr='tagged'):
     """
     Sets the given model class up for working with tags.
     """
+
     if model in registry:
-        raise AlreadyRegistered(
-            _('The model %s has already been registered.') % model.__name__)
-    registry.append(model)
+        raise AlreadyRegistered("The model '%s' has already been "
+            "registered." % model._meta.object_name)
+    if hasattr(model, tag_descriptor_attr):
+        raise AttributeError("'%s' already has an attribute '%s'. You must "
+            "provide a custom tag_descriptor_attr to register." % (
+                model._meta.object_name,
+                tag_descriptor_attr,
+            )
+        )
+    if hasattr(model, tagged_item_manager_attr):
+        raise AttributeError("'%s' already has an attribute '%s'. You must "
+            "provide a custom tagged_item_manager_attr to register." % (
+                model._meta.object_name,
+                tagged_item_manager_attr,
+            )
+        )
 
     # Add tag descriptor
     setattr(model, tag_descriptor_attr, TagDescriptor())
 
     # Add custom manager
-    ModelTaggedItemManager().contribute_to_class(model,
-                                                 tagged_item_manager_attr)
+    ModelTaggedItemManager().contribute_to_class(model, tagged_item_manager_attr)
+
+    # Finally register in registry
+    registry.append(model)