Adding a "new-style" middleware breaks tests

Using Django Mystery Errors
1

I tried adding a TimezoneMiddleware very similar to the one documented in the Django docs

This works great in the web side, but it broke all of my views that were using the Django TestClient. It seems that something about this middleware existing in tests causes the response object to be None in other middlewares, which triggers errors like this one:

======================================================================
ERROR: test_landing_page (apps.web.tests.test_basic_views.TestBasicViews.test_landing_page)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/czue/src/personal/wedding_plan/apps/web/tests/test_basic_views.py", line 7, in test_landing_page
    self._assert_200(reverse("web:home"))
  File "/home/czue/src/personal/wedding_plan/apps/web/tests/test_basic_views.py", line 22, in _assert_200
    response = self.client.get(url)
               ^^^^^^^^^^^^^^^^^^^^
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/test/client.py", line 927, in get
    response = super().get(path, data=data, secure=secure, headers=headers, **extra)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/test/client.py", line 457, in get
    return self.generic(
           ^^^^^^^^^^^^^
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/test/client.py", line 609, in generic
    return self.request(**r)
           ^^^^^^^^^^^^^^^^^
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/test/client.py", line 891, in request
    self.check_exception(response)
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/test/client.py", line 738, in check_exception
    raise exc_value
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
               ^^^^^^^^^^^^^^^^^^^^^
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/utils/deprecation.py", line 136, in __call__
    response = self.process_response(request, response)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/czue/.virtualenvs/wedding_plan/lib/python3.11/site-packages/django/middleware/common.py", line 107, in process_response
    if response.status_code == 404 and self.should_redirect_with_slash(request):
       ^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'status_code'

Switching it from the new-style middleware to the old one (using MiddlewareMixin and process_request, etc.) fixes the tests. But it seems like this path is meant to be deprecated.

Any advice on this?

2

Do you have any code path in your middleware that could possibly result in a response not being returned?

1 Like
3

Duh, yes I did. Thank you for the quick help!