fix _run_authentication creating the coroutine result twice

Author: eugenenelou

ninja/operation.py

@@ -81,9 +81,9 @@ def __init__(
         self.throttle_objects: List[BaseThrottle] = []
         if throttle is not NOT_SET:
             for th in throttle:  # type: ignore
-                assert isinstance(
-                    th, BaseThrottle
-                ), "Throttle should be an instance of BaseThrottle"
+                assert isinstance(th, BaseThrottle), (
+                    "Throttle should be an instance of BaseThrottle"
+                )
                 self.throttle_objects.append(th)
 
         self.signature = ViewSignature(self.path, self.view_func)
@@ -163,9 +163,9 @@ def set_api_instance(self, api: "NinjaAPI", router: "Router") -> None:
             if router.throttle != NOT_SET:
                 _t = router.throttle
                 self.throttle_objects = isinstance(_t, BaseThrottle) and [_t] or _t  # type: ignore
-            assert all(
-                isinstance(th, BaseThrottle) for th in self.throttle_objects
-            ), "Throttle should be an instance of BaseThrottle"
+            assert all(isinstance(th, BaseThrottle) for th in self.throttle_objects), (
+                "Throttle should be an instance of BaseThrottle"
+            )
 
         if self.tags is None:
             if router.tags is not None:
@@ -207,7 +207,11 @@ def _run_authentication(self, request: HttpRequest) -> Optional[HttpResponse]:
                 if is_async_callable(callback) or getattr(callback, "is_async", False):
                     result = callback(request)
                     if inspect.iscoroutine(result):
-                        result = async_to_sync(callback)(request)
+
+                        async def await_result(cor):
+                            return await cor
+
+                        result = async_to_sync(await_result)(result)
                 else:
                     result = callback(request)
             except Exception as exc: