Overriding settings in Django when used by the models

[אורי‎]

https://stackoverflow.com/questions/53953444/overriding-settings-in-django-when-used-by-the-models

We are using Django for Speedy Net and Speedy Match (currently Django 1.11.17, we can't upgrade to a newer version of Django because of one of our requirements, django-modeltranslation). Some of our settings are used by the models. For example:

class USER_SETTINGS(object):
    MIN_USERNAME_LENGTH = 6
    MAX_USERNAME_LENGTH = 40

    MIN_SLUG_LENGTH = 6
    MAX_SLUG_LENGTH = 200

    # Users can register from age 0 to 180, but can't be kept on the site after age 250.
    MIN_AGE_ALLOWED_IN_MODEL = 0  # In years.
    MAX_AGE_ALLOWED_IN_MODEL = 250  # In years.

    MIN_AGE_ALLOWED_IN_FORMS = 0  # In years.
    MAX_AGE_ALLOWED_IN_FORMS = 180  # In years.

    MIN_PASSWORD_LENGTH = 8
    MAX_PASSWORD_LENGTH = 120

    MAX_NUMBER_OF_FRIENDS_ALLOWED = 800

    PASSWORD_VALIDATORS = [
        {
            'NAME': 'speedy.core.accounts.validators.PasswordMinLengthValidator',
        },
        {
            'NAME': 'speedy.core.accounts.validators.PasswordMaxLengthValidator',
        },
    ]

(which is defined in https://github.com/speedy-net/speedy-net/blob/uri_merge_with_master_2018-12-26_a/speedy/net/settings/global_settings.py). And then in the models I use:

from django.conf import settings as django_settings

class User(ValidateUserPasswordMixin, PermissionsMixin, Entity, AbstractBaseUser):
    settings = django_settings.USER_SETTINGS

(and then use attributes of settings, such as settings.MIN_SLUG_LENGTH, in the class).

The problem is, when I try to override such settings in tests (you can see my question & answer on Can I define classes in Django settings, and how can I override such settings in tests?), User.settings remains the same and is not overridden by the settings I tried to override. This is a problem since in the model I passed settings.MIN_SLUG_LENGTH for example to validators, which are also passed other values by other models. Is it possible to define the models and settings in such a way which the correct settings will be used both in production and in tests, including when I want to override them?

I'm aware of this quote from https://docs.djangoproject.com/en/dev/topics/testing/tools/#overriding-settings:

Warning

The settings file contains some settings that are only consulted during initialization of Django internals. If you change them with override_settings, the setting is changed if you access it via the django.conf.settings module, however, Django’s internals access it differently. Effectively, using override_settings() or modify_settings() with these settings is probably not going to do what you expect it to do.

We do not recommend altering the DATABASES setting. Altering the CACHES setting is possible, but a bit tricky if you are using internals that make using of caching, like django.contrib.sessions. For example, you will have to reinitialize the session backend in a test that uses cached sessions and overrides CACHES.

Finally, avoid aliasing your settings as module-level constants as override_settings() won’t work on such values since they are only evaluated the first time the module is imported.

Which I understand are relevant in this case, but how do I define the settings in such a way that I can override them?

Thanks,

אורי (Uri)

u...@speedy.net

אורי

u...@speedy.net

[Jason]

Sounds like what you want is something in https://djangopackages.org/grids/g/live-setting/

This will let you change settings via an admin interface

[אורי‎]

I don't understand why is it relevant to my question? It's not what I asked.

אורי

u...@speedy.net

On Mon, Dec 31, 2018 at 3:12 PM Jason <jjohn...@gmail.com> wrote:

Sounds like what you want is something in https://djangopackages.org/grids/g/live-setting/

This will let you change settings via an admin interface

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[Vinicius Assef]

I hope you already got this solved. If not, there's a way to achieve what you are looking for.

Get settings.MIN_SLUG_LENGTH from an environment variable. Use it in your settings.py:

MIN_SLUG_LENGTH = os.getenv('ENV_MIN_SLUG_LENGTH')

You'll need to set ENV_MIN_SLUG_LENGTH before running your tests in the shell will run them.

Note: ENV_MIN_SLUG_LENGTH could be any name. This is only for demonstration purposes, OK?

Shalom!

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[Carlton Gibson]

Hi Uri. 

Does it work if you make `User.settings` a property, that fetches the values dynamically, rather than assigning them once at import time? 

Something like: 

@property

def settings(self):

    return django_settings.USER_SETTINGS

[אורי‎]

Hi Carlton,

1. I apologize for the time taking me to reply. I had other things to handle before I could handle this issue.

2. The settings in models such as User are per class/model and not per instance. You can see the models in the following file:

https://github.com/speedy-net/speedy-net/blob/staging/speedy/core/accounts/models.py

For example, you can see the following code:

    AGE_VALID_VALUES_IN_MODEL = range(settings.MIN_AGE_ALLOWED_IN_MODEL, settings.MAX_AGE_ALLOWED_IN_MODEL)

    AGE_VALID_VALUES_IN_FORMS = range(settings.MIN_AGE_ALLOWED_IN_FORMS, settings.MAX_AGE_ALLOWED_IN_FORMS)

These constants, for example, are used in the validators:

https://github.com/speedy-net/speedy-net/blob/staging/speedy/core/accounts/validators.py

def age_is_valid_in_model(age):

    from .models import User

    return (age in User.AGE_VALID_VALUES_IN_MODEL)

def age_is_valid_in_forms(age):

    from .models import User

    return (age in User.AGE_VALID_VALUES_IN_FORMS)

And also `User.settings` appears many times in our code.

In general the model in all the project uses the same constant values, except in some tests where I want to override these values in order to test some specific cases which can't be tested with the values used in production. So I'm not sure using a property is the correct thing to do here. I'm looking for a way to define settings per class/model, but in a way that can be overridden in tests.

What do you think?

3. (Currently there is a hack I used in the tests, you can see `def _1___set_up` in https://github.com/speedy-net/speedy-net/blob/staging/speedy/core/base/test/models.py but it's a temporary hack and I don't think it's good as a permanent solution.

By the way, I tried to call the function ___set_up but it didn't work, there is a problem with functions which start with 2 or more underlines.)

4. By the way, `validators` may be a property since it's only used per instance, but I'm not sure about settings. Maybe I can use the settings differently in `validators` and define it there as a property?

אורי

u...@speedy.net

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