feat(config): additionally check /usr/local/share and /usr/share for …

…system-wide config

For some distros (immutable ones?), contents for /etc may not be
easily packaged, so add support for /usr/share locations to help.

This is only enabled for Linux hosts for now, because conventions for
system-wide config files are different on other platforms.

ruyi/config/__init__.py

@@ -2,6 +2,7 @@
 import os.path
 from os import PathLike
 import pathlib
+import sys
 import tomllib
 from typing import Any, Iterable, NotRequired, Self, TypedDict
 
@@ -10,6 +11,16 @@
 from ..utils.xdg_basedir import XDGBaseDir
 from .news import NewsReadStatusStore
 
+PRESET_GLOBAL_CONFIG_LOCATIONS: list[str] = []
+
+if sys.platform == "linux":
+    PRESET_GLOBAL_CONFIG_LOCATIONS = [
+        # TODO: enable distro packagers to customize the $PREFIX to suit their
+        # particular FS layout if necessary.
+        "/usr/share/ruyi/system-wide-config.toml",
+        "/usr/local/share/ruyi/system-wide-config.toml",
+    ]
+
 DEFAULT_APP_NAME = "ruyi"
 DEFAULT_REPO_URL = "https://github.com/ruyisdk/packages-index.git"
 DEFAULT_REPO_BRANCH = "main"
@@ -195,6 +206,16 @@ def ensure_state_dir(self) -> os.PathLike[Any]:
         p.mkdir(parents=True, exist_ok=True)
         return p
 
+    def iter_preset_configs(self) -> Iterable[os.PathLike[Any]]:
+        """
+        Yields possible Ruyi config files in all preset config path locations,
+        sorted by precedence from lowest to highest (so that each file may be
+        simply applied consecutively).
+        """
+
+        for path in PRESET_GLOBAL_CONFIG_LOCATIONS:
+            yield pathlib.Path(path)
+
     def iter_xdg_configs(self) -> Iterable[os.PathLike[Any]]:
         """
         Yields possible Ruyi config files in all XDG config paths, sorted by precedence
@@ -204,20 +225,27 @@ def iter_xdg_configs(self) -> Iterable[os.PathLike[Any]]:
         for config_dir in reversed(list(self._dirs.app_config_dirs)):
             yield config_dir / "config.toml"
 
+    def try_apply_config_file(self, path: os.PathLike[Any]) -> None:
+        try:
+            with open(path, "rb") as fp:
+                data: Any = tomllib.load(fp)
+        except FileNotFoundError:
+            return
+
+        log.D(f"applying config: {data}")
+        self.apply_config(data)
+
     @classmethod
     def load_from_config(cls) -> Self:
         obj = cls()
 
+        for config_path in obj.iter_preset_configs():
+            log.D(f"trying config file from preset location: {config_path}")
+            obj.try_apply_config_file(config_path)
+
         for config_path in obj.iter_xdg_configs():
-            log.D(f"trying config file: {config_path}")
-            try:
-                with open(config_path, "rb") as fp:
-                    data: Any = tomllib.load(fp)
-            except FileNotFoundError:
-                continue
-
-            log.D(f"applying config: {data}")
-            obj.apply_config(data)
+            log.D(f"trying config file from XDG path: {config_path}")
+            obj.try_apply_config_file(config_path)
 
         # let environment variable take precedence
         if is_env_var_truthy(ENV_TELEMETRY_OPTOUT_KEY):