Simple Error Handling for Prefix and App commands - discord.py

error_handler.py

import logging

import discord
from discord import app_commands
from discord.ext import commands


LOGGER: logging.Logger = logging.getLogger(__name__)


class CommandErrors(commands.Cog):
    
    def __init__(self, bot: commands.Bot) -> None:
        # Save the default handlers incase we have to unload this extension...
        self.original_command_error = bot.on_command_error
        self.original_app_error = bot.tree.on_error
        
        # Assign the new handlers to the bot...
        bot.on_command_error = self.on_command_error
        bot.tree.on_error = self.on_app_command_error
        
        self.bot = bot
    
    async def cog_unload(self) -> None:
        """Load the original error handlers back into the bot when this Cog unloads."""
        self.bot.on_command_error = self.original_command_error
        self.bot.tree.on_error = self.original_app_error
        
    async def send(
        self,
        content: str,
        /,
        context: commands.Context[commands.Bot] | discord.Interaction[commands.Bot],
        ephemeral: bool = True
    ) -> None:
        """Simple generic method for sending a response.
        
        This method catches and logs discord.HTTPExceptions.
        
        Parameters
        ----------
        content: str
            The content to send in the response.
        context: commands.Context | discord.Interaction
            The context or interaction surrounding the command or app command.
        ephemeral: bool
            Optional bool indicating whether the repsonse should attempted to be sent ephemerally. Defaults to True.
        """
        if isinstance(context, commands.Context):
            send = context.send
        else:
            send = context.response.send_message if not context.response.is_done() else context.followup.send

        try:
            await send(content=content, ephemeral=ephemeral)
        except discord.HTTPException as e:
            msg = f'Ignoring HTTPException in %r for %r: %s\n\n'
            LOGGER.error(msg, self.send.__name__, self.__class__.__name__, e, exc_info=e)
    
    async def on_command_error(self, ctx: commands.Context[commands.Bot], error: commands.CommandError) -> None:
        """Prefix command error handler."""
        
        # Don't continue if we have a command specific handler...
        if ctx.command and ctx.command.has_error_handler():
            return
        
        # Don't continue if we have a Cog error handler...
        elif ctx.cog and ctx.cog.has_error_handler():
            return
        
        error = getattr(error, 'original', error)
        ignored = (commands.CommandNotFound, commands.NotOwner)
        
        # Don't continue if the error is in ignored...
        if isinstance(error, ignored):
            return
        
        # Example of handling some command errors...
        # If we don't handle the Exception we log it to console...
        elif isinstance(error, commands.NoPrivateMessage):
            await self.send("This command can not be used in Private Messages.", context=ctx)
        elif isinstance(error, commands.DisabledCommand):
            await self.send("This command has been disabled by the owner.", context=ctx)
        else:
            LOGGER.error("Ignoring exception in command %s", ctx.command, exc_info=error)
        
    async def on_app_command_error(
        self,
        interaction: discord.Interaction[commands.Bot],
        error: app_commands.AppCommandError,
    ) -> None:
        """AppCommand error handler."""
        command = interaction.command
        
        # Default logging if the AppCommand is None...
        if command is None:
            LOGGER.error("Ignoring exception in command tree", exc_info=error)
            return
        
        # Don't continue if we have a command specific handler...
        if command.on_error:
            return
        
        # Example of responding to an error...
        if isinstance(error, app_commands.CommandOnCooldown):
            retry_after = error.cooldown.get_retry_after()
            await self.send(f"This command is on cooldown. Try again in {retry_after:.2f} seconds...", context=interaction)
        else:
            # Respond to all unhandled errors as an example... Could be removed to show the default response from Discord.
            # All unhandled errors are also logged to console...
            await self.send(f"**This application received an unhandled exception:**\n\n{error}", context=interaction)
            LOGGER.error('Ignoring exception in command %r', command.name, exc_info=error)


async def setup(bot: commands.Bot) -> None:
    await bot.add_cog(CommandErrors(bot))

error_handler_clean.py

import logging

import discord
from discord import app_commands
from discord.ext import commands


LOGGER: logging.Logger = logging.getLogger(__name__)


class CommandErrors(commands.Cog):
    
    def __init__(self, bot: commands.Bot) -> None:
        self.original_command_error = bot.on_command_error
        self.original_app_error = bot.tree.on_error
        
        bot.on_command_error = self.on_command_error
        bot.tree.on_error = self.on_app_command_error
        
        self.bot = bot
    
    async def cog_unload(self) -> None:
        """Load the original error handlers back into the bot when this Cog unloads."""
        self.bot.on_command_error = self.original_command_error
        self.bot.tree.on_error = self.original_app_error
        
    async def send(
        self,
        content: str,
        /,
        context: commands.Context[commands.Bot] | discord.Interaction[commands.Bot],
        ephemeral: bool = True
    ) -> None:
        """Simple generic method for sending a response.
        
        Parameters
        ----------
        content: str
            The content to send in the response.
        context: commands.Context | discord.Interaction
            The context or interaction surrounding the command or app command.
        ephemeral: bool
            Optional bool indicating whether the repsonse should attempted to be sent ephemerally. Defaults to True.
        """
        if isinstance(context, commands.Context):
            send = context.send
        else:
            send = context.response.send_message if not context.response.is_done() else context.followup.send

        try:
            await send(content=content, ephemeral=ephemeral)
        except discord.HTTPException as e:
            msg = f'Ignoring HTTPException in %r for %r: %s\n\n'
            LOGGER.error(msg, self.send.__name__, self.__class__.__name__, e, exc_info=e)
    
    async def on_command_error(self, ctx: commands.Context[commands.Bot], error: commands.CommandError) -> None:
        """Prefix command error handler."""
        if ctx.command and ctx.command.has_error_handler():
            return
        
        elif ctx.cog and ctx.cog.has_error_handler():
            return
        
        error = getattr(error, 'original', error)
        ignored = (commands.CommandNotFound, commands.NotOwner)
        
        if isinstance(error, ignored):
            return
        
        elif isinstance(error, commands.NoPrivateMessage):
            await self.send("This command can not be used in Private Messages.", context=ctx)
        elif isinstance(error, commands.DisabledCommand):
            await self.send("This command has been disabled by the owner.", context=ctx)
        else:
            LOGGER.error("Ignoring exception in command %s", ctx.command, exc_info=error)
        
    async def on_app_command_error(
        self,
        interaction: discord.Interaction[commands.Bot],
        error: app_commands.AppCommandError,
    ) -> None:
        """AppCommand error handler."""
        command = interaction.command
        
        if command is None:
            LOGGER.error("Ignoring exception in command tree", exc_info=error)
            return
        
        if command.on_error:
            return
        
        if isinstance(error, app_commands.CommandOnCooldown):
            retry_after = error.cooldown.get_retry_after()
            await self.send(f"This command is on cooldown. Try again in {retry_after:.2f} seconds...", context=interaction)
        else:
            await self.send(f"**This application received an unhandled exception:**\n\n{error}", context=interaction)
            LOGGER.error('Ignoring exception in command %r', command.name, exc_info=error)


async def setup(bot: commands.Bot) -> None:
    await bot.add_cog(CommandErrors(bot))

Hey, another example to prevent for the use of on_command_error occurring when __error defined in cogs, use

if hasattr(bot.get_cog(ctx.command.cog_name), '_' + ctx.command.cog_name + '__error'):
        return

Also maybe include __error for in cogs.

@modelmat

Hey, another example to prevent for the use of on_command_error occurring when __error defined in cogs, use

Since this is probably a niche thing, and slightly confusing to those who are not familiar with name mangling, I will keep it from the actual examples. Though should someone want to add that to the global handler...

if hasattr(ctx.cog, f'_{ctx.cog.__class__.__name__}__error'):
    ...  # Do whatever...

Would be a much simpler way of doing this.

The MissingRequiredArgument if statements need to be updated, I'm not sure what changed, whether it was the shift to rewrite or some update of the inspect lib but error.param is a inspect.Parameter object and therefore will always return false in rewrite when compared to a string.

if error.param == 'inp':

has to be replaced by

if error.param.name == 'inp':

Grammar error on L41.

Since 02/23/2019 this Error Handler doesn't work due the cog changes.
So I suggest you to updating:

    @commands.Cog.listener()
    async def on_command_error(self, ctx, error):

class CommandErrorHandler(commands.Cog):

It's an easter egg!

What is this licensed under?

Grammar error on L41.

That's try:

The printing default traceback thing doesn't work

The printing default traceback thing doesn't work

Yeah doesn't work me either

@hello.error
async def hello_error(self, ctx, error):

is it the right way of having arguments

mine not working

mine not working

are you gonna give an error? or say what it is doing? or show your source so people can see what you messed up?

could this possibly be updated because command.has_error_handler and cog.has_error_handler exists?

Using these, we can just put this in the main on_command_error():

if ctx.command.has_error_handler() or ctx.cog.has_error_handler():
    return

Using these, we can just put this in the main on_command_error():

if ctx.command.has_error_handler or ctx.cog.has_error_handler:
    return

Isn't it should be has_error_handler()?

Does anyone know how to handle this error?
'Forbidden: 403 Forbidden (error code: 50001): Missing Access'

@Daudd yea, you're right. Fixed my code.

how to use this in my bot
i mean how to import this

@benjamonnguyen You don't have the right permissions to do whatever you're trying to do

how to use this in my bot i mean how to import this

you dont have to import anything to make use of it. just make sure that its in your cogs folder