override_settings() does not restore partially deleted settings.

[Hodossy, Szabolcs]

When a settings is a dictionary, and only a key in that dicitonary needs to be deleted for a test, the @override_settings() decorator does not restore the original settings value.

It is a common practice for apps to use a single settings dictionary for their own configuration. A quick example can be seen here with the django-auth-adfs package: ​https://github.com/hodossy/django-auth-adfs at commit e11eca87ef96a3a074fc0846feb71183182e53dd.

To reproduce the issue, you can clone the project, install dependecies and run 'python manage.py test' to see test failing with KeyError due to above error.

[Mariusz Felisiak]

Thanks for this report, however it is not a valid usage of the override_settings() decorator (see ​documentation). You can simulate the absence of a setting, but you cannot modify it partially with override_settings(). You should rather create a local copy and override the setting e.g.

    def test_access_callback_azure(self):
        ...
        auth_adfs_setting = settings.AUTH_ADFS.copy()
        del auth_adfs_setting["SERVER"]
        with self.settings(AUTH_ADFS=auth_adfs_setting):
             ...

Closing per TicketClosingReasons/UseSupportChannels.