Jinja2 backend requires settings to be configured

[Jaap Roes]

Importing the Jinja2 backend without configuring settings raises:

django.core.exceptions.ImproperlyConfigured: Requested setting CACHES, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings. .

As far I can tell the Jinja2 backend doesn't need a cache backend to be configured.

[Jaap Roes]

The dependency on the settings is a side effect of importing template.backends.utils.csrf_input_lazy triggering the the import of middleware.csrf.get_token then utils.cache.patch_vary_headers and finally core.cache.caches.

Moving get_token (and maybe rotate_token) to a new module (maybe django.utils.csrf?) would solve this. get_token is imported from at various places throughout the Django codebase.

[Tim Graham]

Could you explain the use case for importing the backend without settings configured?

[Aymeric Augustin]

We're trying to keep as many modules as possible importable without requiring configured settings.

IIRC there was another ticket recently to stop accessing settings at import time when importing django.core.caches. This is the correct approach. The technique proposed here will fix the symptoms for template.backends.utils but not for any other module that imports django.core.caches. I recommend to close this as a duplicate of the other ticket.

[Jaap Roes]

Closing as a duplicate of #25034.

The use case for me was doing some benchmarking on jinja2 VS the cached template loader. (Pretty similar in performance so far).