Bug/expected? Issue with django override_settings

[ivan-gerasin]

Hi, I'm using dynaconf with django and met an issue when using override_settings decorator in test.

    # all correct imports defined, here just a piece of test itsed
    @override_settings(ANY_CONFIG_PARAM='SOME_VAL')
    def test_method_that_use_settings(self):
        # this actually can be any code that call method where somewhere settings.ANY_OTHER_VALUE are used
        # in my case it was django api test client
        print(settings.ANY_OTHER_VALUE) 
        self.assertTrue(True) # just to have any assert

And I got AttributeError. Last part of the stacktrace:

    # all trace before this depends on where settings.ANY_OTHER_VALUE is used. This lines down below are same for all cases
  File "/home/igerasin/projects/project-alpha/venv/lib/python3.8/site-packages/dynaconf/base.py", line 158, in __getattr__
    self._wrapped._fresh
  File "/home/igerasin/projects/project-alpha/venv/lib/python3.8/site-packages/django/conf/__init__.py", line 242, in __getattr__
    raise AttributeError
AttributeError

Is it expected behavior? How can I correctly use override_settings with dynaconf?
Thanks!

[whg517]

I got same issue. And this is a bug.

I use pytest-django, when i use settings fixture to override conf in some test case, i got AttributeError .

analysis

Django code logic

In django.test.utils.py

class override_settings(TestContextDecorator):
    """
    Act as either a decorator or a context manager. If it's a decorator, take a
    function and return a wrapped function. If it's a contextmanager, use it
    with the ``with`` statement. In either event, entering/exiting are called
    before and after, respectively, the function/block is executed.
    """
    enable_exception = None

    def __init__(self, **kwargs):
        self.options = kwargs
        super().__init__()

    def enable(self):
        # Keep this code at the beginning to leave the settings unchanged
        # in case it raises an exception because INSTALLED_APPS is invalid.
        if 'INSTALLED_APPS' in self.options:
            try:
                apps.set_installed_apps(self.options['INSTALLED_APPS'])
            except Exception:
                apps.unset_installed_apps()
                raise
        override = UserSettingsHolder(settings._wrapped)
        for key, new_value in self.options.items():
            setattr(override, key, new_value)
        self.wrapped = settings._wrapped
        settings._wrapped = override
        for key, new_value in self.options.items():
            try:
                setting_changed.send(
                    sender=settings._wrapped.__class__,
                    setting=key, value=new_value, enter=True,
                )
            except Exception as exc:
                self.enable_exception = exc
                self.disable()

The settings._wrapped is UserSettingsHolder object.

And django.conf.__init__.py::UserSettingsHolder class

class UserSettingsHolder:
    """Holder for user configured settings."""
    # SETTINGS_MODULE doesn't make much sense in the manually configured
    # (standalone) case.
    SETTINGS_MODULE = None

    def __init__(self, default_settings):
        """
        Requests for configuration variables not in this class are satisfied
        from the module specified in default_settings (if possible).
        """
        self.__dict__['_deleted'] = set()
        self.default_settings = default_settings

    def __getattr__(self, name):
        if not name.isupper() or name in self._deleted:
            raise AttributeError
        return getattr(self.default_settings, name)

If you get a attr is not upper, will raise a AttributeError .

Dynaconf code logic

In dynaconf.base.py::LazySettings class

https://github.com/rochacbruno/dynaconf/blob/6c6fda4950a1a403b71503c8940692aeb3725cdf/dynaconf/base.py#L116-L123

When you get a attr, dynaconf will get it from settings._wrapped, but now settings._wrapped is django.conf.__init__.py::UserSettingsHolder .

So there's an exception.

---

I knew what the problem was, and I wanted to fix it. But I'm not clear about the complex logic in Dynaconf's 'Settings' class, and I don't have much time to understand the source code at this stage, so I won't commit PR. But I hope this problem can be fixed soon.

[rochacbruno]

Solution is proposed in #643