[Bot] update extension loading

Author: YaoxuanZhang

capy_discord/bot.py

@@ -2,7 +2,7 @@
 
 from discord.ext.commands import AutoShardedBot
 
-from capy_discord.utils.extensions import EXTENSIONS
+from capy_discord.utils import EXTENSIONS
 
 
 class Bot(AutoShardedBot):

capy_discord/utils/__init__.py

@@ -0,0 +1 @@
+from capy_discord.utils.extensions import EXTENSIONS

capy_discord/utils/extensions.py

@@ -0,0 +1,57 @@
+# MIT License
+#
+# Copyright (c) 2018 Python Discord
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+import importlib
+import inspect
+import pkgutil
+from collections.abc import Iterator
+from typing import NoReturn
+
+from capy_discord import exts
+
+
+def unqualify(name: str) -> str:
+    """Return an unqualified name given a qualified module/package `name`."""
+    return name.rsplit(".", maxsplit=1)[-1]
+
+
+def walk_extensions() -> Iterator[str]:
+    """Yield extension names from the bot.exts subpackage."""
+
+    def on_error(name: str) -> NoReturn:
+        raise ImportError(name=name)  # pragma: no cover
+
+    for module in pkgutil.walk_packages(exts.__path__, f"{exts.__name__}.", onerror=on_error):
+        if unqualify(module.name).startswith("_"):
+            # Ignore module/package names starting with an underscore.
+            continue
+
+        if module.ispkg:
+            imported = importlib.import_module(module.name)
+            if not inspect.isfunction(getattr(imported, "setup", None)):
+                # If it lacks a setup function, it's not an extension.
+                continue
+
+        yield module.name
+
+
+EXTENSIONS = frozenset(walk_extensions())