refactor!(settings): Simplify settings structure

src/robots/settings.py

@@ -1,23 +1,44 @@
 import sys
+import typing as t
 
+from django.conf import settings
+from django.test.signals import setting_changed
 
-class Settings:
-    defaults = {
-        #: A list of one or more sitemaps to inform robots about:
-        "SITEMAP_URLS": ("ROBOTS_SITEMAP_URLS", []),
-        "USE_SITEMAP": ("ROBOTS_USE_SITEMAP", True),
-        "USE_HOST": ("ROBOTS_USE_HOST", True),
-        "CACHE_TIMEOUT": ("ROBOTS_CACHE_TIMEOUT", None),
-        "SITE_BY_REQUEST": ("ROBOTS_SITE_BY_REQUEST", False),
-        "USE_SCHEME_IN_HOST": ("ROBOTS_USE_SCHEME_IN_HOST", False),
-        "SITEMAP_VIEW_NAME": ("ROBOTS_SITEMAP_VIEW_NAME", False),
-    }
+DEFAULT_ROBOTS_SETTINGS: t.Dict[str, t.Any] = {
+    "SITEMAP_URLS": [],
+    "USE_SITEMAP": True,
+    "USE_HOST": True,
+    "CACHE_TIMEOUT": None,
+    "SITE_BY_REQUEST": False,
+    "USE_SCHEME_IN_HOST": False,
+    "SITEMAP_VIEW_NAME": False,
+}
 
-    def __getattr__(self, attribute):
-        from django.conf import settings
 
-        if attribute in self.defaults:
-            return getattr(settings, *self.defaults[attribute])
+def getdefault(setting: str) -> t.Any:
+    return getattr(settings, f"ROBOTS_{setting}", DEFAULT_ROBOTS_SETTINGS[setting])
 
 
-sys.modules[__name__] = Settings()
+SITEMAP_URLS: t.List[str] = getdefault("SITEMAP_URLS")
+USE_SITEMAP: bool = getdefault("USE_SITEMAP")
+USE_HOST: bool = getdefault("USE_HOST")
+CACHE_TIMEOUT: t.Optional[int] = getdefault("CACHE_TIMEOUT")
+SITE_BY_REQUEST: bool = getdefault("SITE_BY_REQUEST")
+USE_SCHEME_IN_HOST: bool = getdefault("USE_SCHEME_IN_HOST")
+SITEMAP_VIEW_NAME: bool = getdefault("SITEMAP_VIEW_NAME")
+
+
+def reload_robots_settings(
+    setting: str, value: t.Any, enter: bool, **kwargs: object
+) -> None:
+    if not setting.startswith("ROBOTS_"):  # pragma: nocover
+        return
+
+    setting = setting.replace("ROBOTS_", "")
+    if enter:  # setting applied
+        setattr(sys.modules[__name__], setting, value)
+    else:
+        setattr(sys.modules[__name__], setting, getdefault(setting))
+
+
+setting_changed.connect(reload_robots_settings)