#34174: async process_exception being called as sync from async view/middleware
-------------------------------------+-------------------------------------
Reporter: Gabriel Rado | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Documentation | Version: 4.1
Severity: Normal | Resolution:
Keywords: middleware async | Triage Stage:
process_exception | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Gabriel Rado:
Old description:
> following this bold part of the
> docs[https://docs.djangoproject.com/en/4.1/topics/http/middleware
> /#asynchronous-support]:
>
> process_view, process_template_response and process_exception methods, if
> they are provided, **should also be adapted to match the sync/async
> mode**. However, Django will individually adapt them as required if you
> do not, at an additional performance penalty.
>
> I' using this middleware to parse errors from sync and async views:
>
> {{{
> @sync_and_async_middleware
> def custom_error(get_response):
> if asyncio.iscoroutinefunction(get_response):
>
> async def middleware(request):
> response = await get_response(request)
> return response
>
> async def _process_exception(request, exception):
> return my_custom_process_exception(exception)
>
> else:
>
> def middleware(request):
> response = get_response(request)
> return response
>
> def _process_exception(request, exception):
> return my_custom_process_exception(exception)
>
> middleware.process_exception = _process_exception
> return middleware
> }}}
>
> and I'm getting "ValueError: The view my_view.view_func didn't return an
> HttpResponse object. It returned an unawaited coroutine instead. You may
> need to add an 'await' into your view." from
> here[https://github.com/django/django/blob/main/django/core/handlers/base.py#L257]
>
> i thought that with an async middleware + async view, all my hooks
> (process_view, process_template_response and process_exception) should be
> also async, but it appears that is mandatory to use sync
> process_exception with async capable middlewares. if this is intended,
> could the official docs be changed to expose this mandatory behavior?
New description:
following this bold part from
[https://docs.djangoproject.com/en/4.1/topics/http/middleware
/#asynchronous-support]:
> process_view, process_template_response and process_exception methods,
if they are provided, **should also be adapted to match the sync/async
mode**. However, Django will individually adapt them as required if you do
not, at an additional performance penalty.
I'm using this middleware to parse errors from sync and async views:
{{{
@sync_and_async_middleware
def custom_error(get_response):
if asyncio.iscoroutinefunction(get_response):
async def middleware(request):
response = await get_response(request)
return response
async def _process_exception(request, exception):
return my_custom_process_exception(exception)
else:
def middleware(request):
response = get_response(request)
return response
def _process_exception(request, exception):
return my_custom_process_exception(exception)
middleware.process_exception = _process_exception
return middleware
}}}
and I'm getting "ValueError: The view my_view.view_func didn't return an
HttpResponse object. It returned an unawaited coroutine instead. You may
need to add an 'await' into your view." from
[https://github.com/django/django/blob/main/django/core/handlers/base.py#L257]
i thought that with an async middleware + async view, all my hooks
(process_view, process_template_response and process_exception) should be
also async, but it appears that is mandatory to use sync process_exception
with async capable middlewares. if this is intended, could the official
docs be changed to expose this mandatory behavior?
--
--
Ticket URL: <https://code.djangoproject.com/ticket/34174#comment:1>
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