Fixed #31224 -- Added support for asynchronous views and middleware.

This implements support for asynchronous views, asynchronous tests,
asynchronous middleware, and an asynchronous test client.

tests/middleware_exceptions/middleware.py

@@ -1,6 +1,9 @@
 from django.http import Http404, HttpResponse
 from django.template import engines
 from django.template.response import TemplateResponse
+from django.utils.decorators import (
+    async_only_middleware, sync_and_async_middleware, sync_only_middleware,
+)
 
 log = []
 
@@ -18,6 +21,12 @@ class ProcessExceptionMiddleware(BaseMiddleware):
         return HttpResponse('Exception caught')
 
 
+@async_only_middleware
+class AsyncProcessExceptionMiddleware(BaseMiddleware):
+    async def process_exception(self, request, exception):
+        return HttpResponse('Exception caught')
+
+
 class ProcessExceptionLogMiddleware(BaseMiddleware):
     def process_exception(self, request, exception):
         log.append('process-exception')
@@ -33,6 +42,12 @@ class ProcessViewMiddleware(BaseMiddleware):
         return HttpResponse('Processed view %s' % view_func.__name__)
 
 
+@async_only_middleware
+class AsyncProcessViewMiddleware(BaseMiddleware):
+    async def process_view(self, request, view_func, view_args, view_kwargs):
+        return HttpResponse('Processed view %s' % view_func.__name__)
+
+
 class ProcessViewNoneMiddleware(BaseMiddleware):
     def process_view(self, request, view_func, view_args, view_kwargs):
         log.append('processed view %s' % view_func.__name__)
@@ -51,6 +66,13 @@ class TemplateResponseMiddleware(BaseMiddleware):
         return response
 
 
+@async_only_middleware
+class AsyncTemplateResponseMiddleware(BaseMiddleware):
+    async def process_template_response(self, request, response):
+        response.context_data['mw'].append(self.__class__.__name__)
+        return response
+
+
 class LogMiddleware(BaseMiddleware):
     def __call__(self, request):
         response = self.get_response(request)
@@ -63,6 +85,48 @@ class NoTemplateResponseMiddleware(BaseMiddleware):
         return None
 
 
+@async_only_middleware
+class AsyncNoTemplateResponseMiddleware(BaseMiddleware):
+    async def process_template_response(self, request, response):
+        return None
+
+
 class NotFoundMiddleware(BaseMiddleware):
     def __call__(self, request):
         raise Http404('not found')
+
+
+class TeapotMiddleware(BaseMiddleware):
+    def __call__(self, request):
+        response = self.get_response(request)
+        response.status_code = 418
+        return response
+
+
+@async_only_middleware
+def async_teapot_middleware(get_response):
+    async def middleware(request):
+        response = await get_response(request)
+        response.status_code = 418
+        return response
+
+    return middleware
+
+
+@sync_and_async_middleware
+class SyncAndAsyncMiddleware(BaseMiddleware):
+    pass
+
+
+@sync_only_middleware
+class DecoratedTeapotMiddleware(TeapotMiddleware):
+    pass
+
+
+class NotSyncOrAsyncMiddleware(BaseMiddleware):
+    """Middleware that is deliberately neither sync or async."""
+    sync_capable = False
+    async_capable = False
+
+    def __call__(self, request):
+        return self.get_response(request)