From 8c5b4ec59fec3c415247b79d8642a8b68b9d8040 Mon Sep 17 00:00:00 2001
From: ddorn <diego.dorn@free.fr>
Date: Wed, 29 Apr 2020 15:14:35 +0200
Subject: [PATCH] :recycle: more flexible error handling

---
 src/cogs/errors.py      | 94 +++++++++++++++++++++++++++++++++++++++++
 src/tfjm_discord_bot.py | 42 +++---------------
 2 files changed, 99 insertions(+), 37 deletions(-)

diff --git a/src/cogs/errors.py b/src/cogs/errors.py
index e69de29..df560f3 100644
--- a/src/cogs/errors.py
+++ b/src/cogs/errors.py
@@ -0,0 +1,94 @@
+import sys
+import traceback
+
+import discord
+from discord.ext.commands import *
+from discord.utils import maybe_coroutine
+
+from src.errors import UnwantedCommand
+
+
+# Global variable and function because I'm too lazy to make a metaclass
+handlers = {}
+
+
+def handles(error_type):
+    """
+    This registers an error handler.
+
+    Error handlers can be coroutines or functions.
+    """
+
+    def decorator(f):
+        handlers[error_type] = f
+        return f
+
+    return decorator
+
+
+class ErrorsCog(Cog):
+    """This cog defines all the handles for errors."""
+
+    @Cog.listener()
+    async def on_command_error(self, ctx: Context, error: CommandError):
+        print(repr(error), file=sys.stderr)
+
+        # We take the first superclass with an handler defined
+        handler = None
+        for type_ in error.__class__.__mro__:
+            handler = handlers.get(type_)
+            if handler:
+                break
+
+        if handler is None:
+            # Default handling
+            msg = repr(error)
+        else:
+            msg = await maybe_coroutine(handler, self, ctx, error)
+
+        if msg:
+            await ctx.send(msg)
+
+    @handles(UnwantedCommand)
+    async def on_unwanted_command(self, ctx, error):
+        await ctx.message.delete()
+        author: discord.Message
+        await ctx.author.send(
+            "J'ai supprimé ton message:\n> "
+            + ctx.message.clean_content
+            + "\nC'est pas grave, c'est juste pour ne pas encombrer "
+            "le chat lors du tirage."
+        )
+        await ctx.author.send("Raison: " + error.original.msg)
+
+    @handles(CommandInvokeError)
+    async def on_command_invoke_error(self, ctx, error):
+        specific_handler = handlers.get(type(error.original))
+
+        if specific_handler:
+            return await specific_handler(ctx, error)
+
+        traceback.print_tb(error.original.__traceback__, file=sys.stderr)
+        return (
+            error.original.__class__.__name__
+            + ": "
+            + (str(error.original) or str(error))
+        )
+
+    @handles(CommandNotFound)
+    def on_command_not_found(self, ctx, error):
+
+        # Here we just take advantage that the error is formatted this way:
+        # 'Command "NAME" is not found'
+        name = str(error).partition('"')[2].rpartition('"')[0]
+        return f"La commande {name} n'éxiste pas. Pour une liste des commandes, envoie `!help`."
+
+    @handles(MissingRole)
+    def on_missing_role(self, ctx, error):
+        return (
+            f"Il te faut le role de {error.missing_role} pour utiliser cette commande."
+        )
+
+
+def setup(bot):
+    bot.add_cog(ErrorsCog())
diff --git a/src/tfjm_discord_bot.py b/src/tfjm_discord_bot.py
index 44d6e7a..ba4cdc3 100644
--- a/src/tfjm_discord_bot.py
+++ b/src/tfjm_discord_bot.py
@@ -18,6 +18,8 @@ from src.errors import TfjmError, UnwantedCommand
 bot = commands.Bot(("! ", "!"), help_command=TfjmHelpCommand())
 
 # Variable globale qui contient les tirages.
+# We *want* it to be global so we can reload the tirages cog without
+# removing all the running tirages
 tirages = {}
 
 
@@ -26,46 +28,12 @@ async def on_ready():
     print(f"{bot.user} has connected to Discord!")
 
 
-@bot.event
-async def on_command_error(ctx: Context, error, *args, **kwargs):
-    if isinstance(error, commands.CommandInvokeError):
-        if isinstance(error.original, UnwantedCommand):
-            await ctx.message.delete()
-            author: discord.Message
-            await ctx.author.send(
-                "J'ai supprimé ton message:\n> "
-                + ctx.message.clean_content
-                + "\nC'est pas grave, c'est juste pour ne pas encombrer "
-                "le chat lors du tirage."
-            )
-            await ctx.author.send("Raison: " + error.original.msg)
-            return
-        else:
-            msg = (
-                error.original.__class__.__name__
-                + ": "
-                + (str(error.original) or str(error))
-            )
-            traceback.print_tb(error.original.__traceback__, file=sys.stderr)
-    elif isinstance(error, commands.CommandNotFound):
-        # Here we just take adventage that the error is formatted this way:
-        # 'Command "NAME" is not found'
-        name = str(error).partition('"')[2].rpartition('"')[0]
-        msg = f"La commande {name} n'éxiste pas. Pour un liste des commandes, envoie `!help`."
-    elif isinstance(error, commands.MissingRole):
-        msg = f"Il te faut le role de {error.missing_role} pour utiliser cette commande"
-    else:
-        msg = repr(error)
-
-    print(repr(error), dir(error), file=sys.stderr)
-    await ctx.send(msg)
-
-
 bot.remove_command("help")
-bot.load_extension("src.cogs.tirages")
-bot.load_extension("src.cogs.teams")
 bot.load_extension("src.cogs.dev")
+bot.load_extension("src.cogs.errors")
 bot.load_extension("src.cogs.misc")
+bot.load_extension("src.cogs.teams")
+bot.load_extension("src.cogs.tirages")
 
 
 if __name__ == "__main__":