Fixed #33611 -- Allowed View subclasses to define async method handlers.

tests/async/tests.py

@@ -1,3 +1,4 @@
+import asyncio
 import os
 import sys
 from unittest import mock, skipIf
@@ -5,9 +6,11 @@ from unittest import mock, skipIf
 from asgiref.sync import async_to_sync
 
 from django.core.cache import DEFAULT_CACHE_ALIAS, caches
-from django.core.exceptions import SynchronousOnlyOperation
+from django.core.exceptions import ImproperlyConfigured, SynchronousOnlyOperation
+from django.http import HttpResponse
 from django.test import SimpleTestCase
 from django.utils.asyncio import async_unsafe
+from django.views.generic.base import View
 
 from .models import SimpleModel
 
@@ -72,3 +75,66 @@ class AsyncUnsafeTest(SimpleTestCase):
             self.dangerous_method()
         except SynchronousOnlyOperation:
             self.fail("SynchronousOnlyOperation should not be raised.")
+
+
+class SyncView(View):
+    def get(self, request, *args, **kwargs):
+        return HttpResponse("Hello (sync) world!")
+
+
+class AsyncView(View):
+    async def get(self, request, *args, **kwargs):
+        return HttpResponse("Hello (async) world!")
+
+
+class ViewTests(SimpleTestCase):
+    def test_views_are_correctly_marked(self):
+        tests = [
+            (SyncView, False),
+            (AsyncView, True),
+        ]
+        for view_cls, is_async in tests:
+            with self.subTest(view_cls=view_cls, is_async=is_async):
+                self.assertIs(view_cls.view_is_async, is_async)
+                callback = view_cls.as_view()
+                self.assertIs(asyncio.iscoroutinefunction(callback), is_async)
+
+    def test_mixed_views_raise_error(self):
+        class MixedView(View):
+            def get(self, request, *args, **kwargs):
+                return HttpResponse("Hello (mixed) world!")
+
+            async def post(self, request, *args, **kwargs):
+                return HttpResponse("Hello (mixed) world!")
+
+        msg = (
+            f"{MixedView.__qualname__} HTTP handlers must either be all sync or all "
+            "async."
+        )
+        with self.assertRaisesMessage(ImproperlyConfigured, msg):
+            MixedView.as_view()
+
+    def test_options_handler_responds_correctly(self):
+        tests = [
+            (SyncView, False),
+            (AsyncView, True),
+        ]
+        for view_cls, is_coroutine in tests:
+            with self.subTest(view_cls=view_cls, is_coroutine=is_coroutine):
+                instance = view_cls()
+                response = instance.options(None)
+                self.assertIs(
+                    asyncio.iscoroutine(response),
+                    is_coroutine,
+                )
+                if is_coroutine:
+                    response = asyncio.run(response)
+
+                self.assertIsInstance(response, HttpResponse)
+
+    def test_base_view_class_is_sync(self):
+        """
+        View and by extension any subclasses that don't define handlers are
+        sync.
+        """
+        self.assertIs(View.view_is_async, False)