Added route checking before add to route to prevent duplication

Author: kevinluvian

rest_framework_extensions/routers.py

@@ -80,20 +80,27 @@ def get_routes(self, viewset):
             if self.is_dynamic_route(route):
                 # Dynamic routes (@list_route or @detail_route decorator)
                 if self.is_list_dynamic_route(route):
-                    ret += self.get_dynamic_routes_instances(
+                    temporary_route_list = self.get_dynamic_routes_instances(
                         viewset,
                         route,
                         self._filter_by_list_dynamic_routes(dynamic_routes)
                     )
+                    for temporary_route in temporary_route_list:
+                        if temporary_route not in ret:
+                            ret.append(temporary_route)
                 else:
-                    ret += self.get_dynamic_routes_instances(
+                    temporary_route_list = self.get_dynamic_routes_instances(
                         viewset,
                         route,
                         self._filter_by_detail_dynamic_routes(dynamic_routes)
                     )
+                    for temporary_route in temporary_route_list:
+                        if temporary_route not in ret:
+                            ret.append(temporary_route)
             else:
                 # Standard route
-                ret.append(route)
+                if route not in ret:
+                    ret.append(route)
 
         return ret