@method_decorator can't be used on async view at class-level with name="dispatch"

[Jacob Walls]

@method_decorator(..., name="dispatch") doesn't work for async views that don't override dispatch(), because dispatch() is sync, which is enough to fool the logic in #35083.

tests/decorators/test_cache.py

@@ +1 @@
+from http import HTTPStatus
 from inspect import iscoroutinefunction
 from unittest import mock
 
@@ -5 +6 @@
 from django.test import SimpleTestCase
 from django.utils.decorators import method_decorator
 from django.views.decorators.cache import cache_control, cache_page, never_cache
+from django.views.generic import View
 
 
 class HttpRequestProxy:
@@ -217 +219 @@
         with self.assertRaisesMessage(TypeError, msg):
             await MyClass().async_view(HttpRequestProxy(request))
 
+    async def test_never_cache_method_decorator_http_request_async_view(self):
+        @method_decorator(never_cache, name="dispatch")
+        class MyClass(View):
+            async def get(self, request):
+                return HttpResponse()
+
+        request = HttpRequest()
+        request.method = "GET"
+        response = await MyClass().dispatch(request)
+        self.assertEqual(response.status_code, HTTPStatus.OK)
+
     def test_never_cache_decorator_http_request_proxy(self):
         class MyClass:
             @method_decorator(never_cache)

ERROR: test_never_cache_method_decorator_http_request_async_view (decorators.test_cache.NeverCacheDecoratorTest.test_never_cache_method_decorator_http_request_async_view)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/jwalls/my314/lib/python3.14/site-packages/asgiref/sync.py", line 325, in __call__
    return call_result.result()
           ~~~~~~~~~~~~~~~~~~^^
  File "/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/concurrent/futures/_base.py", line 443, in result
    return self.__get_result()
           ~~~~~~~~~~~~~~~~~^^
  File "/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/concurrent/futures/_base.py", line 395, in __get_result
    raise self._exception
  File "/Users/jwalls/my314/lib/python3.14/site-packages/asgiref/sync.py", line 365, in main_wrap
    result = await awaitable
             ^^^^^^^^^^^^^^^
  File "/Users/jwalls/django/tests/decorators/test_cache.py", line 230, in test_never_cache_method_decorator_http_request_async_view
    response = await MyClass().dispatch(request)
                     ~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/Users/jwalls/django/django/utils/decorators.py", line 47, in _wrapper
    return bound_method(*args, **kwargs)
  File "/Users/jwalls/django/django/views/decorators/cache.py", line 80, in _view_wrapper
    add_never_cache_headers(response)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/Users/jwalls/django/django/utils/cache.py", line 294, in add_never_cache_headers
    patch_response_headers(response, cache_timeout=-1)
    ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jwalls/django/django/utils/cache.py", line 285, in patch_response_headers
    if not response.has_header("Expires"):
           ^^^^^^^^^^^^^^^^^^^
AttributeError: 'coroutine' object has no attribute 'has_header'

---

Moving the decorator to the method instead of the class works. We probably will prefer a test inside the test class added in #35083 rather than merging my sketched test.

[Vishy Algo]

Hi Jacob,

Please take a look at the PR and let me know whether patching View with __init_subclass__ would be an appropriate fix, or if it would be considered out of scope for this ticket.

[Carlton Gibson]

This is a doozy. I'm not convinced it's tractable... (at reasonable cost/complexity to method_decorator).

If the method being decorated is not async then it's not 100% clear to me that method_decorator should do any further introspection to determine if the return value should be marked as a coroutine.

We're asking it to decorate a method, and #35083 was about allowing those methods to be async. Both conjuncts work.

Moving the decorator to the method instead of the class works.

A further know significant details about the particulars of View strikes me as out of scope for method_decorator.

If I had to decorate dispatch for an async view class, I think this is probably the best option:

    @method_decorator(never_cache, name="dispatch")
    class MyClass(View):
        async def dispatch(self, *args, **kwargs):
            return super().dispatch(*args, **kwargs)    

 	async def get(self, request):
 	     return HttpResponse()

(Not tested. You get the idea)

This somewhat mitigates using the name="dispatch" — so I'd probably put it on the method directly, and I'd only need to do that if we also had say async def post as well.

But I think trying to automagically our way forward here is mistake. It's complex. It just is.

So I think a docs tweak is probably the way to go.

[Vishy Algo]

I completely agree, inspecting the return value and patching feels more like over-engineering than necessary.

But would async get dispatch cause any issues, if handled incorrectly! Cause, when just overriding dispatch (without http methods) also seems to be a mistake.

Probably as_view should also be overridden (again when all http methods are sync, view_is_async is False).

[Carlton Gibson]

It makes no sense to override dispatch to be async except in this kind of case.