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)

tests/middleware_exceptions/tests.py

@@ -180,3 +180,162 @@ class MiddlewareNotUsedTests(SimpleTestCase):
         with self.assertRaisesMessage(AssertionError, 'no logs'):
             with self.assertLogs('django.request', 'DEBUG'):
                 self.client.get('/middleware_exceptions/view/')
+
+
+@override_settings(
+    DEBUG=True,
+    ROOT_URLCONF='middleware_exceptions.urls',
+)
+class MiddlewareSyncAsyncTests(SimpleTestCase):
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.TeapotMiddleware',
+    ])
+    def test_sync_teapot_middleware(self):
+        response = self.client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.status_code, 418)
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.DecoratedTeapotMiddleware',
+    ])
+    def test_sync_decorated_teapot_middleware(self):
+        response = self.client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.status_code, 418)
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.async_teapot_middleware',
+    ])
+    def test_async_teapot_middleware(self):
+        with self.assertLogs('django.request', 'DEBUG') as cm:
+            response = self.client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.status_code, 418)
+        self.assertEqual(
+            cm.records[0].getMessage(),
+            "Synchronous middleware "
+            "middleware_exceptions.middleware.async_teapot_middleware "
+            "adapted.",
+        )
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.NotSyncOrAsyncMiddleware',
+    ])
+    def test_not_sync_or_async_middleware(self):
+        msg = (
+            'Middleware '
+            'middleware_exceptions.middleware.NotSyncOrAsyncMiddleware must '
+            'have at least one of sync_capable/async_capable set to True.'
+        )
+        with self.assertRaisesMessage(RuntimeError, msg):
+            self.client.get('/middleware_exceptions/view/')
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.TeapotMiddleware',
+    ])
+    async def test_sync_teapot_middleware_async(self):
+        with self.assertLogs('django.request', 'DEBUG') as cm:
+            response = await self.async_client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.status_code, 418)
+        self.assertEqual(
+            cm.records[0].getMessage(),
+            "Asynchronous middleware "
+            "middleware_exceptions.middleware.TeapotMiddleware adapted.",
+        )
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.async_teapot_middleware',
+    ])
+    async def test_async_teapot_middleware_async(self):
+        with self.assertLogs('django.request', 'WARNING') as cm:
+            response = await self.async_client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.status_code, 418)
+        self.assertEqual(
+            cm.records[0].getMessage(),
+            'Unknown Status Code: /middleware_exceptions/view/',
+        )
+
+    @override_settings(
+        DEBUG=False,
+        MIDDLEWARE=[
+            'middleware_exceptions.middleware.AsyncNoTemplateResponseMiddleware',
+        ],
+    )
+    def test_async_process_template_response_returns_none_with_sync_client(self):
+        msg = (
+            "AsyncNoTemplateResponseMiddleware.process_template_response "
+            "didn't return an HttpResponse object."
+        )
+        with self.assertRaisesMessage(ValueError, msg):
+            self.client.get('/middleware_exceptions/template_response/')
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.SyncAndAsyncMiddleware',
+    ])
+    async def test_async_and_sync_middleware_async_call(self):
+        response = await self.async_client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.content, b'OK')
+        self.assertEqual(response.status_code, 200)
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.SyncAndAsyncMiddleware',
+    ])
+    def test_async_and_sync_middleware_sync_call(self):
+        response = self.client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.content, b'OK')
+        self.assertEqual(response.status_code, 200)
+
+
+@override_settings(ROOT_URLCONF='middleware_exceptions.urls')
+class AsyncMiddlewareTests(SimpleTestCase):
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.AsyncTemplateResponseMiddleware',
+    ])
+    async def test_process_template_response(self):
+        response = await self.async_client.get(
+            '/middleware_exceptions/template_response/'
+        )
+        self.assertEqual(
+            response.content,
+            b'template_response OK\nAsyncTemplateResponseMiddleware',
+        )
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.AsyncNoTemplateResponseMiddleware',
+    ])
+    async def test_process_template_response_returns_none(self):
+        msg = (
+            "AsyncNoTemplateResponseMiddleware.process_template_response "
+            "didn't return an HttpResponse object. It returned None instead."
+        )
+        with self.assertRaisesMessage(ValueError, msg):
+            await self.async_client.get('/middleware_exceptions/template_response/')
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.AsyncProcessExceptionMiddleware',
+    ])
+    async def test_exception_in_render_passed_to_process_exception(self):
+        response = await self.async_client.get(
+            '/middleware_exceptions/exception_in_render/'
+        )
+        self.assertEqual(response.content, b'Exception caught')
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.AsyncProcessExceptionMiddleware',
+    ])
+    async def test_exception_in_async_render_passed_to_process_exception(self):
+        response = await self.async_client.get(
+            '/middleware_exceptions/async_exception_in_render/'
+        )
+        self.assertEqual(response.content, b'Exception caught')
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.AsyncProcessExceptionMiddleware',
+    ])
+    async def test_view_exception_handled_by_process_exception(self):
+        response = await self.async_client.get('/middleware_exceptions/error/')
+        self.assertEqual(response.content, b'Exception caught')
+
+    @override_settings(MIDDLEWARE=[
+        'middleware_exceptions.middleware.AsyncProcessViewMiddleware',
+    ])
+    async def test_process_view_return_response(self):
+        response = await self.async_client.get('/middleware_exceptions/view/')
+        self.assertEqual(response.content, b'Processed view normal_view')

tests/middleware_exceptions/urls.py

@@ -8,4 +8,9 @@ urlpatterns = [
     path('middleware_exceptions/permission_denied/', views.permission_denied),
     path('middleware_exceptions/exception_in_render/', views.exception_in_render),
     path('middleware_exceptions/template_response/', views.template_response),
+    # Async views.
+    path(
+        'middleware_exceptions/async_exception_in_render/',
+        views.async_exception_in_render,
+    ),
 ]

tests/middleware_exceptions/views.py

@@ -27,3 +27,11 @@ def exception_in_render(request):
             raise Exception('Exception in HttpResponse.render()')
 
     return CustomHttpResponse('Error')
+
+
+async def async_exception_in_render(request):
+    class CustomHttpResponse(HttpResponse):
+        async def render(self):
+            raise Exception('Exception in HttpResponse.render()')
+
+    return CustomHttpResponse('Error')