[3.1.x] Fixed #31928 -- Fixed detecting an async get_response in various middlewares.

SecurityMiddleware and the three cache middlewares were not calling
super().__init__() during their initialization or calling the required
MiddlewareMixin._async_check() method.

This made the middlewares not properly present as coroutine and
confused the middleware chain when used in a fully async context.

Thanks Kordian Kowalski for the report.

Backport of 825ce75faec63ce81601e31152c757a9c28fed13 from master

1 files changed, 24 insertions, 0 deletions

diff --git a/tests/deprecation/test_middleware_mixin.py b/tests/deprecation/test_middleware_mixin.py
index c90aeb8360..02987ff961 100644
--- a/tests/deprecation/test_middleware_mixin.py
+++ b/tests/deprecation/test_middleware_mixin.py
@@ -1,3 +1,4 @@
+import asyncio
 import threading
 
 from asgiref.sync import async_to_sync
@@ -45,6 +46,29 @@ class MiddlewareMixinTests(SimpleTestCase):
                 with self.assertRaisesMessage(RemovedInDjango40Warning, self.msg):
                     middleware()
 
+    def test_coroutine(self):
+        async def async_get_response(request):
+            return HttpResponse()
+
+        def sync_get_response(request):
+            return HttpResponse()
+
+        for middleware in [
+            CacheMiddleware,
+            FetchFromCacheMiddleware,
+            UpdateCacheMiddleware,
+            SecurityMiddleware,
+        ]:
+            with self.subTest(middleware=middleware.__qualname__):
+                # Middleware appears as coroutine if get_function is
+                # a coroutine.
+                middleware_instance = middleware(async_get_response)
+                self.assertIs(asyncio.iscoroutinefunction(middleware_instance), True)
+                # Middleware doesn't appear as coroutine if get_function is not
+                # a coroutine.
+                middleware_instance = middleware(sync_get_response)
+                self.assertIs(asyncio.iscoroutinefunction(middleware_instance), False)
+
     def test_sync_to_async_uses_base_thread_and_connection(self):
         """
         The process_request() and process_response() hooks must be called with