Allow override_config for pytest

[TamoshaytisV]

override_config is currently possible to apply only to unittest TestCase classes.
This PR adds constance.test.pytest module that can be used as follows

Examples can be found in doc

It's still possible to do import as usual for unittest

from constance.test import override_config

...

[camilonova]

Vladas thank you for your contribution. Why this is needed?

[TamoshaytisV]

There are a lot of django projects where i use pytest as a test runner. Django-constance forces me to use TestCase inheritance to make override work
I have the workaround to set CONSTANCE_CONFIG values in test.py settings but often i want to have different overrides for specific methods or classes

@camilonova please let me know if it's clear enough

[camilonova]

Got it. I'm not able to make a decision here. Maybe @jezdez knows best.

[jezdez]

Thanks @camilonova for raising this with me, I agree that this is a non-trivial feature that we need to discuss first.

In general I'm in favor of improving the use of override_config when used with Pytest. But I'm not sure if providing a decorator like override_config fits the best practices of the Pytest community.

E.g. pytest-django didn't implement a custom overrride_settings decorator to override Django's settings but instead chose to implement a Pytest fixture that allows modifying of settings in the test session.

Similarly I would encourage you to implement this feature as a constance or config fixture that would have the ability to override config values during individual tests. I would consider that to be a more practical user experience than having to know which decorator to use.

[TamoshaytisV]

@jezdez I agree that for pytest it's better to use fixtures or markers but what initially stopped me from implementing in that way is complexity to make it work preserving simplicity of decorator and ability to change config for any scope.
I will investigate more using pytest-django example and will get back with results soon.
Thank you

[jezdez]

@jezdez I agree that for pytest it's better to use fixtures or markers but what initially stopped me from implementing in that way is complexity to make it work preserving simplicity of decorator and ability to change config for any scope.

I understand, and appreciate your openness to investigate this further. As always I try to apply the mantra "it's easy to add, but is it also easy to maintain?" to such discussion. Your input and contribution is valued and welcome nevertheless.

I will investigate more using pytest-django example and will get back with results soon.
Thank you

[TamoshaytisV]

@jezdez @camilonova sorry for being inactive for a long time. I finalized refactoring and feature in general, please review or feel free to assign propper reviewers if you are not available.

[TamoshaytisV]

Probably the need to have __setattr__ in this class may appear in future but ATM i can't think of many usage cases and all they can be solved using context manager or using fixture and marking tests/classes/modules

[marco-silva0000]

I like what's been done here, I'm using a copy paste on my code and it makes tests really clean.
+1 for this to be merged in

[TamoshaytisV]

@jezdez will you be so kind to assign other reviewers if you are busy with smth else?

[pawelzar]

Nice work @TamoshaytisV 👍. I have a few suggestions - instead of pytest.mark and ConstanceConfigWrapper and override_config fixture we could define override_config as ContextDecorator which could server both as decorator and context manager.

[camilonova]

Please check the latest changes/comments and I would be happy to merge this.

Thank you all!

[TamoshaytisV]

@pawelzar I used ContextDecorator so now it's possible to use override_config in the same way as it is for unittest + context manager. Nevertheless, I insist to keep fixture and mark so users can use it in pytest way but with less code

[camilonova]

Thank you all

[utapyngo]

Is this going to be released soon?

[camilonova]

If someone can confirm it works fine if the package is installed from master I can make a release

[TamoshaytisV]

I've tried it in my project with

-e git+https://github.com/jazzband/django-constance.git#egg=constance[database]

I've got the warning
WARNING: Generating metadata for package constance produced metadata for project name django-constance. Fix your #egg=constance fragments.

In fact, lib was really installed with database backend anyway, so in general, it's working
Can someone please correct my egg= part and also try it as I'm not sure what's the correct way to specify extras_require for github URL requirement?

[Mogost]

Need something like here (in pytest-django) to prevent #410

Suggested change

	marker = item.get_closest_marker("override_config")
	if not django_settings_is_configured():
	return
	marker = item.get_closest_marker("override_config")