Django silently ignores settings that were removed in older versions - how do I find them?
I maintain a Django project that has been around since Django 1.11 and has been upgraded step by step to 5.2. The upgrades themselves went fine — tests are green, everything runs.
What worries me is settings.py. It has grown for years and I'm fairly sure there are leftovers in there that do absolutely nothing anymore:
# settings.py (excerpt)
TEMPLATE_DIRS = [BASE_DIR / "templates"] # ???
SEND_BROKEN_LINK_EMAILS = True # ???
USE_L10N = True
FILE_CHARSET = "utf-8"
DEFAULT_FILE_STORAGE = "storages.backends.s3boto3.S3Boto3Storage"
The problem is that Django never complains about any of this. The settings object is essentially a namespace — if nothing reads an attribute, the attribute is just dead weight. python manage.py check is happy, runserver is happy, the tests are happy. TEMPLATE_DIRS has been ignored since 1.10 and I only found out by accident.
What I tried:
Deprecation warnings (
python -Wall manage.py check). These only help while a feature is deprecated. Once it's actually removed, the code that emitted the warning is gone too, so you get silence. For a project that skipped several versions, that window has long closed.django-upgrade/pyupgrade. Great tools, but they rewrite code patterns (ugettext,url(), ...). They don't tell me that a settings variable stopped having any effect five versions ago.Reading the release notes. The "Features removed in X" section exists for every release, but going through 30+ releases by hand and diffing that against my settings is not something I want to do again on the next upgrade.
Is there a way to get this checked automatically — ideally as part of the regular manage.py check run so I can wire it into CI?