From 40165eecc40f9e223702a41a0cb0958515bb1f82 Mon Sep 17 00:00:00 2001
From: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Date: Thu, 16 Dec 2021 20:13:17 +0100
Subject: [PATCH] Fixed #33350 -- Reallowed using cache decorators with
 duck-typed HttpRequest.

Regression in 3fd82a62415e748002435e7bad06b5017507777c.

Thanks Terence Honles for the report.
---
 django/views/decorators/cache.py |  7 +++---
 docs/releases/4.0.1.txt          |  4 ++++
 tests/decorators/tests.py        | 41 ++++++++++++++++++++++++++++++--
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/django/views/decorators/cache.py b/django/views/decorators/cache.py
index fdc5917738..417f3614f8 100644
--- a/django/views/decorators/cache.py
+++ b/django/views/decorators/cache.py
@@ -1,6 +1,5 @@
 from functools import wraps
 
-from django.http import HttpRequest
 from django.middleware.cache import CacheMiddleware
 from django.utils.cache import add_never_cache_headers, patch_cache_control
 from django.utils.decorators import decorator_from_middleware_with_args
@@ -29,7 +28,8 @@ def cache_control(**kwargs):
     def _cache_controller(viewfunc):
         @wraps(viewfunc)
         def _cache_controlled(request, *args, **kw):
-            if not isinstance(request, HttpRequest):
+            # Ensure argument looks like a request.
+            if not hasattr(request, 'META'):
                 raise TypeError(
                     "cache_control didn't receive an HttpRequest. If you are "
                     "decorating a classmethod, be sure to use "
@@ -48,7 +48,8 @@ def never_cache(view_func):
     """
     @wraps(view_func)
     def _wrapped_view_func(request, *args, **kwargs):
-        if not isinstance(request, HttpRequest):
+        # Ensure argument looks like a request.
+        if not hasattr(request, 'META'):
             raise TypeError(
                 "never_cache didn't receive an HttpRequest. If you are "
                 "decorating a classmethod, be sure to use @method_decorator."
diff --git a/docs/releases/4.0.1.txt b/docs/releases/4.0.1.txt
index 08e5b206bb..50c84bfe17 100644
--- a/docs/releases/4.0.1.txt
+++ b/docs/releases/4.0.1.txt
@@ -15,3 +15,7 @@ Bugfixes
 
 * Fixed a bug in Django 4.0 that caused a crash on booleans with the
   ``RedisCache`` backend (:ticket:`33361`).
+
+* Relaxed the check added in Django 4.0 to reallow use of a duck-typed
+  ``HttpRequest`` in ``django.views.decorators.cache.cache_control()`` and
+  ``never_cache()`` decorators (:ticket:`33350`).
diff --git a/tests/decorators/tests.py b/tests/decorators/tests.py
index de0edaa787..b9d16f9a1b 100644
--- a/tests/decorators/tests.py
+++ b/tests/decorators/tests.py
@@ -493,6 +493,15 @@ class XFrameOptionsDecoratorsTests(TestCase):
         self.assertIsNone(r.get('X-Frame-Options', None))
 
 
+class HttpRequestProxy:
+    def __init__(self, request):
+        self._request = request
+
+    def __getattr__(self, attr):
+        """Proxy to the underlying HttpRequest object."""
+        return getattr(self._request, attr)
+
+
 class NeverCacheDecoratorTest(SimpleTestCase):
 
     @mock.patch('time.time')
@@ -525,12 +534,27 @@ class NeverCacheDecoratorTest(SimpleTestCase):
             @never_cache
             def a_view(self, request):
                 return HttpResponse()
+
+        request = HttpRequest()
         msg = (
             "never_cache didn't receive an HttpRequest. If you are decorating "
             "a classmethod, be sure to use @method_decorator."
         )
         with self.assertRaisesMessage(TypeError, msg):
-            MyClass().a_view(HttpRequest())
+            MyClass().a_view(request)
+        with self.assertRaisesMessage(TypeError, msg):
+            MyClass().a_view(HttpRequestProxy(request))
+
+    def test_never_cache_decorator_http_request_proxy(self):
+        class MyClass:
+            @method_decorator(never_cache)
+            def a_view(self, request):
+                return HttpResponse()
+
+        request = HttpRequest()
+        response = MyClass().a_view(HttpRequestProxy(request))
+        self.assertIn('Cache-Control', response.headers)
+        self.assertIn('Expires', response.headers)
 
 
 class CacheControlDecoratorTest(SimpleTestCase):
@@ -544,5 +568,18 @@ class CacheControlDecoratorTest(SimpleTestCase):
             "cache_control didn't receive an HttpRequest. If you are "
             "decorating a classmethod, be sure to use @method_decorator."
         )
+        request = HttpRequest()
         with self.assertRaisesMessage(TypeError, msg):
-            MyClass().a_view(HttpRequest())
+            MyClass().a_view(request)
+        with self.assertRaisesMessage(TypeError, msg):
+            MyClass().a_view(HttpRequestProxy(request))
+
+    def test_cache_control_decorator_http_request_proxy(self):
+        class MyClass:
+            @method_decorator(cache_control(a='b'))
+            def a_view(self, request):
+                return HttpResponse()
+
+        request = HttpRequest()
+        response = MyClass().a_view(HttpRequestProxy(request))
+        self.assertEqual(response.headers['Cache-Control'], 'a=b')