most settingchanged receivers are supposed to be added below except for cases where the receiver is related to a contrib app settings that may not work well when using overridesettings 19031 rebuild any appdirectoriesfinder instance rebuild management commands cache rebuild getapptemplatedirs cache rebuild translations cache reset process time zone reset local time zone cache reset the database connections time zone considering the current implementation of the signals framework this stacklevel shows the line containing the overridesettings call some tests set an invalid authusermodel most setting_changed receivers are supposed to be added below except for cases where the receiver is related to a contrib app settings that may not work well when using override_settings 19031 rebuild any appdirectoriesfinder instance rebuild management commands cache rebuild get_app_template_dirs cache rebuild translations cache reset process time zone reset local time zone cache reset the database connections time zone considering the current implementation of the signals framework this stacklevel shows the line containing the override_settings call some tests set an invalid auth_user_model
import os
import time
import warnings

from asgiref.local import Local

from django.apps import apps
from django.core.exceptions import ImproperlyConfigured
from django.core.signals import setting_changed
from django.db import connections, router
from django.db.utils import ConnectionRouter
from django.dispatch import Signal, receiver
from django.utils import timezone
from django.utils.formats import FORMAT_SETTINGS, reset_format_cache
from django.utils.functional import empty

template_rendered = Signal()





COMPLEX_OVERRIDE_SETTINGS = {"DATABASES"}


@receiver(setting_changed)
def clear_cache_handlers(*, setting, **kwargs):
    if setting == "CACHES":
        from django.core.cache import caches, close_caches

        close_caches()
        caches._settings = caches.settings = caches.configure_settings(None)
        caches._connections = Local()


@receiver(setting_changed)
def update_installed_apps(*, setting, **kwargs):
    if setting == "INSTALLED_APPS":
        
        from django.contrib.staticfiles.finders import get_finder

        get_finder.cache_clear()
        
        from django.core.management import get_commands

        get_commands.cache_clear()
        
        from django.template.utils import get_app_template_dirs

        get_app_template_dirs.cache_clear()
        
        from django.utils.translation import trans_real

        trans_real._translations = {}


@receiver(setting_changed)
def update_connections_time_zone(*, setting, **kwargs):
    if setting == "TIME_ZONE":
        
        if hasattr(time, "tzset"):
            if kwargs["value"]:
                os.environ["TZ"] = kwargs["value"]
            else:
                os.environ.pop("TZ", None)
            time.tzset()

        
        timezone.get_default_timezone.cache_clear()

    
    if setting in {"TIME_ZONE", "USE_TZ"}:
        for conn in connections.all(initialized_only=True):
            try:
                del conn.timezone
            except AttributeError:
                pass
            try:
                del conn.timezone_name
            except AttributeError:
                pass
            conn.ensure_timezone()


@receiver(setting_changed)
def clear_routers_cache(*, setting, **kwargs):
    if setting == "DATABASE_ROUTERS":
        router.routers = ConnectionRouter().routers


@receiver(setting_changed)
def reset_template_engines(*, setting, **kwargs):
    if setting in {
        "TEMPLATES",
        "DEBUG",
        "INSTALLED_APPS",
    }:
        from django.template import engines

        try:
            del engines.templates
        except AttributeError:
            pass
        engines._templates = None
        engines._engines = {}
        from django.template.engine import Engine

        Engine.get_default.cache_clear()
        from django.forms.renderers import get_default_renderer

        get_default_renderer.cache_clear()


@receiver(setting_changed)
def storages_changed(*, setting, **kwargs):
    from django.contrib.staticfiles.storage import staticfiles_storage
    from django.core.files.storage import default_storage, storages

    if setting in (
        "STORAGES",
        "STATIC_ROOT",
        "STATIC_URL",
    ):
        try:
            del storages.backends
        except AttributeError:
            pass
        storages._backends = None
        storages._storages = {}

        default_storage._wrapped = empty
        staticfiles_storage._wrapped = empty


@receiver(setting_changed)
def clear_serializers_cache(*, setting, **kwargs):
    if setting == "SERIALIZATION_MODULES":
        from django.core import serializers

        serializers._serializers = {}


@receiver(setting_changed)
def language_changed(*, setting, **kwargs):
    if setting in {"LANGUAGES", "LANGUAGE_CODE", "LOCALE_PATHS"}:
        from django.utils.translation import trans_real

        trans_real._default = None
        trans_real._active = Local()
    if setting in {"LANGUAGES", "LOCALE_PATHS"}:
        from django.utils.translation import trans_real

        trans_real._translations = {}
        trans_real.check_for_language.cache_clear()


@receiver(setting_changed)
def localize_settings_changed(*, setting, **kwargs):
    if setting in FORMAT_SETTINGS or setting == "USE_THOUSAND_SEPARATOR":
        reset_format_cache()


@receiver(setting_changed)
def complex_setting_changed(*, enter, setting, **kwargs):
    if enter and setting in COMPLEX_OVERRIDE_SETTINGS:
        
        
        warnings.warn(
            f"Overriding setting {setting} can lead to unexpected behavior.",
            stacklevel=5,
        )


@receiver(setting_changed)
def root_urlconf_changed(*, setting, **kwargs):
    if setting == "ROOT_URLCONF":
        from django.urls import clear_url_caches, set_urlconf

        clear_url_caches()
        set_urlconf(None)


@receiver(setting_changed)
def static_storage_changed(*, setting, **kwargs):
    if setting in {
        "STATIC_ROOT",
        "STATIC_URL",
    }:
        from django.contrib.staticfiles.storage import staticfiles_storage

        staticfiles_storage._wrapped = empty


@receiver(setting_changed)
def static_finders_changed(*, setting, **kwargs):
    if setting in {
        "STATICFILES_DIRS",
        "STATIC_ROOT",
    }:
        from django.contrib.staticfiles.finders import get_finder

        get_finder.cache_clear()


@receiver(setting_changed)
def form_renderer_changed(*, setting, **kwargs):
    if setting == "FORM_RENDERER":
        from django.forms.renderers import get_default_renderer

        get_default_renderer.cache_clear()


@receiver(setting_changed)
def auth_password_validators_changed(*, setting, **kwargs):
    if setting == "AUTH_PASSWORD_VALIDATORS":
        from django.contrib.auth.password_validation import (
            get_default_password_validators,
        )

        get_default_password_validators.cache_clear()


@receiver(setting_changed)
def user_model_swapped(*, setting, **kwargs):
    if setting == "AUTH_USER_MODEL":
        apps.clear_cache()
        try:
            from django.contrib.auth import get_user_model

            UserModel = get_user_model()
        except ImproperlyConfigured:
            
            pass
        else:
            from django.contrib.auth import backends

            backends.UserModel = UserModel

            from django.contrib.auth import forms

            forms.UserModel = UserModel

            from django.contrib.auth.handlers import modwsgi

            modwsgi.UserModel = UserModel

            from django.contrib.auth.management.commands import changepassword

            changepassword.UserModel = UserModel

            from django.contrib.auth import views

            views.UserModel = UserModel