Refs #26601 -- Made get_response argument required and don't accept None in middleware classes.

Per deprecation timeline.

django/contrib/redirects/middleware.py

@@ -12,7 +12,7 @@ class RedirectFallbackMiddleware(MiddlewareMixin):
     response_gone_class = HttpResponseGone
     response_redirect_class = HttpResponsePermanentRedirect
 
-    def __init__(self, get_response=None):
+    def __init__(self, get_response):
         if not apps.is_installed('django.contrib.sites'):
             raise ImproperlyConfigured(
                 "You cannot use RedirectFallbackMiddleware when "

django/contrib/sessions/middleware.py

@@ -10,9 +10,7 @@ from django.utils.http import http_date
 
 
 class SessionMiddleware(MiddlewareMixin):
-    # RemovedInDjango40Warning: when the deprecation ends, replace with:
-    #   def __init__(self, get_response):
-    def __init__(self, get_response=None):
+    def __init__(self, get_response):
         super().__init__(get_response)
         engine = import_module(settings.SESSION_ENGINE)
         self.SessionStore = engine.SessionStore

django/middleware/cache.py

@@ -61,9 +61,7 @@ class UpdateCacheMiddleware(MiddlewareMixin):
     UpdateCacheMiddleware must be the first piece of middleware in MIDDLEWARE
     so that it'll get called last during the response phase.
     """
-    # RemovedInDjango40Warning: when the deprecation ends, replace with:
-    #   def __init__(self, get_response):
-    def __init__(self, get_response=None):
+    def __init__(self, get_response):
         super().__init__(get_response)
         self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
         self.page_timeout = None
@@ -124,9 +122,7 @@ class FetchFromCacheMiddleware(MiddlewareMixin):
     FetchFromCacheMiddleware must be the last piece of middleware in MIDDLEWARE
     so that it'll get called last during the request phase.
     """
-    # RemovedInDjango40Warning: when the deprecation ends, replace with:
-    #   def __init__(self, get_response):
-    def __init__(self, get_response=None):
+    def __init__(self, get_response):
         super().__init__(get_response)
         self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
         self.cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
@@ -168,9 +164,7 @@ class CacheMiddleware(UpdateCacheMiddleware, FetchFromCacheMiddleware):
     Also used as the hook point for the cache decorator, which is generated
     using the decorator-from-middleware utility.
     """
-    # RemovedInDjango40Warning: when the deprecation ends, replace with:
-    #   def __init__(self, get_response, cache_timeout=None, page_timeout=None, **kwargs):
-    def __init__(self, get_response=None, cache_timeout=None, page_timeout=None, **kwargs):
+    def __init__(self, get_response, cache_timeout=None, page_timeout=None, **kwargs):
         super().__init__(get_response)
         # We need to differentiate between "provided, but using default value",
         # and "not provided". If the value is provided using a default, then

django/middleware/security.py

@@ -6,9 +6,7 @@ from django.utils.deprecation import MiddlewareMixin
 
 
 class SecurityMiddleware(MiddlewareMixin):
-    # RemovedInDjango40Warning: when the deprecation ends, replace with:
-    #   def __init__(self, get_response):
-    def __init__(self, get_response=None):
+    def __init__(self, get_response):
         super().__init__(get_response)
         self.sts_seconds = settings.SECURE_HSTS_SECONDS
         self.sts_include_subdomains = settings.SECURE_HSTS_INCLUDE_SUBDOMAINS

django/utils/deprecation.py

@@ -89,10 +89,9 @@ class MiddlewareMixin:
     sync_capable = True
     async_capable = True
 
-    # RemovedInDjango40Warning: when the deprecation ends, replace with:
-    #   def __init__(self, get_response):
-    def __init__(self, get_response=None):
-        self._get_response_none_deprecation(get_response)
+    def __init__(self, get_response):
+        if get_response is None:
+            raise ValueError('get_response must be provided.')
         self.get_response = get_response
         self._async_check()
         super().__init__()
@@ -137,11 +136,3 @@ class MiddlewareMixin:
                 thread_sensitive=True,
             )(request, response)
         return response
-
-    def _get_response_none_deprecation(self, get_response):
-        if get_response is None:
-            warnings.warn(
-                'Passing None for the middleware get_response argument is '
-                'deprecated.',
-                RemovedInDjango40Warning, stacklevel=3,
-            )

docs/releases/4.0.txt

@@ -295,3 +295,7 @@ to remove usage of these features.
 
 * Support for the pre-Django 3.1 user sessions (that use the SHA-1 algorithm)
   is removed.
+
+* The ``get_request`` argument for
+  ``django.utils.deprecation.MiddlewareMixin.__init__()`` is required and
+  doesn't accept ``None``.

tests/deprecation/test_middleware_mixin.py

@@ -28,14 +28,10 @@ from django.middleware.http import ConditionalGetMiddleware
 from django.middleware.locale import LocaleMiddleware
 from django.middleware.security import SecurityMiddleware
 from django.test import SimpleTestCase
-from django.utils.deprecation import MiddlewareMixin, RemovedInDjango40Warning
+from django.utils.deprecation import MiddlewareMixin
 
 
 class MiddlewareMixinTests(SimpleTestCase):
-    """
-    Deprecation warning is raised when using get_response=None.
-    """
-    msg = 'Passing None for the middleware get_response argument is deprecated.'
     middlewares = [
         AuthenticationMiddleware,
         BrokenLinkEmailsMiddleware,
@@ -58,16 +54,11 @@ class MiddlewareMixinTests(SimpleTestCase):
         XViewMiddleware,
     ]
 
-    def test_deprecation(self):
-        for middleware in self.middlewares:
-            with self.subTest(middleware=middleware):
-                with self.assertRaisesMessage(RemovedInDjango40Warning, self.msg):
-                    middleware()
-
     def test_passing_explicit_none(self):
+        msg = 'get_response must be provided.'
         for middleware in self.middlewares:
             with self.subTest(middleware=middleware):
-                with self.assertRaisesMessage(RemovedInDjango40Warning, self.msg):
+                with self.assertRaisesMessage(ValueError, msg):
                     middleware(None)
 
     def test_coroutine(self):

tests/redirects_tests/tests.py

@@ -3,7 +3,9 @@ from django.contrib.redirects.middleware import RedirectFallbackMiddleware
 from django.contrib.redirects.models import Redirect
 from django.contrib.sites.models import Site
 from django.core.exceptions import ImproperlyConfigured
-from django.http import HttpResponseForbidden, HttpResponseRedirect
+from django.http import (
+    HttpResponse, HttpResponseForbidden, HttpResponseRedirect,
+)
 from django.test import TestCase, modify_settings, override_settings
 
 
@@ -58,12 +60,15 @@ class RedirectTests(TestCase):
 
     @modify_settings(INSTALLED_APPS={'remove': 'django.contrib.sites'})
     def test_sites_not_installed(self):
+        def get_response(request):
+            return HttpResponse()
+
         msg = (
             'You cannot use RedirectFallbackMiddleware when '
             'django.contrib.sites is not installed.'
         )
         with self.assertRaisesMessage(ImproperlyConfigured, msg):
-            RedirectFallbackMiddleware()
+            RedirectFallbackMiddleware(get_response)
 
 
 class OverriddenRedirectFallbackMiddleware(RedirectFallbackMiddleware):