Add a command error handler

Author: Lekuruu

app/bot.py

@@ -16,6 +16,7 @@ async def load_cogs(self):
         await self.load_extension("app.commands.kms")
         await self.load_extension("app.commands.link")
         await self.load_extension("app.commands.bancho")
+        await self.load_extension("app.commands.errors")
         await self.tree.sync()
 
 def run():

app/commands/errors.py

@@ -0,0 +1,32 @@
+
+from discord.ext.commands import *
+from app.cog import BaseCog
+
+class ErrorHandler(BaseCog):
+    @Cog.listener()
+    async def on_command_error(self, ctx: Context, error: CommandError):
+        if hasattr(ctx.command, "on_error"):
+            # Ignore errors that already have a local handler
+            return
+
+        if isinstance(error, CommandNotFound):
+            return
+
+        elif isinstance(error, MissingRequiredArgument):
+            return await ctx.send(f"Missing argument: `{error.param.name}`")
+
+        elif isinstance(error, MissingPermissions):
+            return await ctx.send("You don't have permission to use this command.")
+
+        elif isinstance(error, CommandOnCooldown):
+            return await ctx.send(
+                f"This command is on cooldown. Try again in "
+                f"{error.retry_after:.1f} seconds."
+            )
+
+        # Log unexpected errors
+        self.logger.error(f'Unexpected error: {error}', exc_info=True)
+        await ctx.send("An unexpected error occurred.")
+
+async def setup(bot: Bot):
+    await bot.add_cog(ErrorHandler())