Fixed #24877 -- Added middleware handling of response.render() errors.

django/core/handlers/base.py

@@ -146,15 +146,7 @@ class BaseHandler(object):
                 try:
                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
                 except Exception as e:
-                    # If the view raised an exception, run it through exception
+                    response = self.process_exception_by_middleware(e, request)
-                    # middleware, and if the exception middleware returns a
-                    # response, use that. Otherwise, reraise the exception.
-                    for middleware_method in self._exception_middleware:
-                        response = middleware_method(request, e)
-                        if response:
-                            break
-                    if response is None:
-                        raise
 
             # Complain if the view returned None (a common error).
             if response is None:
@@ -176,7 +168,11 @@ class BaseHandler(object):
                             "%s.process_template_response didn't return an "
                             "HttpResponse object. It returned None instead."
                             % (middleware_method.__self__.__class__.__name__))
-                response = response.render()
+                try:
+                    response = response.render()
+                except Exception as e:
+                    response = self.process_exception_by_middleware(e, request)
+
                 response_is_rendered = True
 
         except http.Http404 as exc:
@@ -257,6 +253,17 @@ class BaseHandler(object):
 
         return response
 
+    def process_exception_by_middleware(self, exception, request):
+        """
+        Pass the exception to the exception middleware. If no middleware
+        return a response for this exception, raise it.
+        """
+        for middleware_method in self._exception_middleware:
+            response = middleware_method(request, exception)
+            if response:
+                return response
+        raise
+
     def handle_uncaught_exception(self, request, resolver, exc_info):
         """
         Processing for any otherwise uncaught exceptions (those that will

docs/releases/1.9.txt

@@ -480,6 +480,9 @@ Requests and Responses
   :class:`~django.template.response.TemplateResponse`, commonly used with
   class-based views.
 
+* Exceptions raised by the ``render()`` method are now passed to the
+  ``process_exception()`` method of each middleware.
+
 * Request middleware can now set :attr:`HttpRequest.urlconf
   <django.http.HttpRequest.urlconf>` to ``None`` to revert any changes made
   by previous middleware and return to using the :setting:`ROOT_URLCONF`.

tests/middleware_exceptions/middleware.py

@@ -0,0 +1,8 @@
+from __future__ import unicode_literals
+
+from django.http import HttpResponse
+
+
+class ProcessExceptionMiddleware(object):
+    def process_exception(self, request, exception):
+        return HttpResponse('Exception caught')

tests/middleware_exceptions/tests.py

@@ -486,6 +486,16 @@ class MiddlewareTests(BaseMiddlewareExceptionTest):
         # Check that the right middleware methods have been invoked
         self.assert_middleware_usage(middleware, True, True, True, True, False)
 
+    @override_settings(
+        MIDDLEWARE_CLASSES=['middleware_exceptions.middleware.ProcessExceptionMiddleware'],
+    )
+    def test_exception_in_render_passed_to_process_exception(self):
+        # Repopulate the list of middlewares since it's already been populated
+        # by setUp() before the MIDDLEWARE_CLASSES setting got overridden
+        self.client.handler.load_middleware()
+        response = self.client.get('/middleware_exceptions/exception_in_render/')
+        self.assertEqual(response.content, b'Exception caught')
+
 
 class BadMiddlewareTests(BaseMiddlewareExceptionTest):
 

tests/middleware_exceptions/urls.py

@@ -8,6 +8,7 @@ urlpatterns = [
     url(r'^middleware_exceptions/error/$', views.server_error),
     url(r'^middleware_exceptions/null_view/$', views.null_view),
     url(r'^middleware_exceptions/permission_denied/$', views.permission_denied),
+    url(r'^middleware_exceptions/exception_in_render/$', views.exception_in_render),
 
     url(r'^middleware_exceptions/template_response/$', views.template_response),
     url(r'^middleware_exceptions/template_response_error/$', views.template_response_error),

tests/middleware_exceptions/views.py

@@ -32,3 +32,11 @@ def null_view(request):
 
 def permission_denied(request):
     raise PermissionDenied()
+
+
+def exception_in_render(request):
+    class CustomHttpResponse(http.HttpResponse):
+        def render(self):
+            raise Exception('Exception in HttpResponse.render()')
+
+    return CustomHttpResponse('Error')