Ticket #7800: gfk-from-option.diff

django/contrib/contenttypes/generic.py

@@ -38 +38 @@
         # Connect myself as the descriptor for this field
         setattr(cls, name, self)
 
+        # Register my in the model's options
+        # Is this a race waiting to happen?
+        gfks = getattr(cls._meta, 'generic_foreign_keys', [])
+        gfks.append(self)
+        setattr(cls._meta, 'generic_foreign_keys', gfks) 
+        
+
     def instance_pre_init(self, signal, sender, args, kwargs, **_kwargs):
         """
         Handles initializing an object with the generic FK instaed of
@@ -112 +119 @@
         self.creates_table = False
 
         # Override content-type/object-id field names on the related class
-        self.object_id_field_name = kwargs.pop("object_id_field", "object_id")
-        self.content_type_field_name = kwargs.pop("content_type_field", "content_type")
+        #self.object_id_field_name = kwargs.pop("object_id_field", "object_id")
+        #self.content_type_field_name = kwargs.pop("content_type_field", "content_type")
+        from_field = kwargs.pop('from', None)
+        to_generic_fks = [field for field in getattr(to._meta, 'generic_foreign_keys', [])
+                          if (field.__class__ == GenericForeignKey
+                              and (from_field and (from_field == field.name) or True))]
+        exc_args = {'named': from_field and (" named '%s'" % from_field) or "",
+                    'to_model': to._meta.object_name,
+                    'specify': from_field and "" or ": Specify one with the 'from' argument."}
+        if len(to_generic_fks) == 0:
+            raise Exception("No GenericForeignKey field%(named)s on '%(to_model)s' to relate to." % exc_args)
+        elif len(to_generic_fks) > 1:
+            raise Exception("Multiple GenericForeignKey fields%(named)s on '%(to_model)s' to relate to%(specify)s" % exc_args)
 
+        gfk = to_generic_fks[0]
+        self.object_id_field_name = gfk.fk_field
+        self.content_type_field_name = gfk.ct_field
+
+
         kwargs['blank'] = True
         kwargs['editable'] = False
         kwargs['serialize'] = False