Merge pull request #392 from python-discord/django-readd-events

Re-add command error event handler

6 files changed, 125 insertions, 20 deletions

diff --git a/bot/__main__.py b/bot/__main__.py
index b3f80ef55..4bc7d1202 100644
--- a/bot/__main__.py
+++ b/bot/__main__.py
@@ -31,6 +31,7 @@ bot.http_session = ClientSession(
 bot.api_client = APIClient(loop=asyncio.get_event_loop())
 
 # Internal/debug
+bot.load_extension("bot.cogs.error_handler")
 bot.load_extension("bot.cogs.filtering")
 bot.load_extension("bot.cogs.logging")
 bot.load_extension("bot.cogs.modlog")
diff --git a/bot/api.py b/bot/api.py
index 2e1a239ba..e926a262e 100644
--- a/bot/api.py
+++ b/bot/api.py
@@ -5,6 +5,11 @@ import aiohttp
 from .constants import Keys, URLs
 
 
+class ResponseCodeError(ValueError):
+    def __init__(self, response: aiohttp.ClientResponse):
+        self.response = response
+
+
 class APIClient:
     def __init__(self, **kwargs):
         auth_headers = {
@@ -16,33 +21,40 @@ class APIClient:
         else:
             kwargs['headers'] = auth_headers
 
-        self.session = aiohttp.ClientSession(
-            **kwargs,
-            raise_for_status=True
-        )
+        self.session = aiohttp.ClientSession(**kwargs)
 
     @staticmethod
     def _url_for(endpoint: str):
         return f"{URLs.site_schema}{URLs.site_api}/{quote_url(endpoint)}"
 
-    async def get(self, endpoint: str, *args, **kwargs):
+    def maybe_raise_for_status(self, response: aiohttp.ClientResponse, should_raise: bool):
+        if should_raise and response.status >= 400:
+            raise ResponseCodeError(response=response)
+
+    async def get(self, endpoint: str, *args, raise_for_status: bool = True, **kwargs):
         async with self.session.get(self._url_for(endpoint), *args, **kwargs) as resp:
+            self.maybe_raise_for_status(resp, raise_for_status)
             return await resp.json()
 
-    async def patch(self, endpoint: str, *args, **kwargs):
+    async def patch(self, endpoint: str, *args, raise_for_status: bool = True, **kwargs):
         async with self.session.patch(self._url_for(endpoint), *args, **kwargs) as resp:
+            self.maybe_raise_for_status(resp, raise_for_status)
             return await resp.json()
 
-    async def post(self, endpoint: str, *args, **kwargs):
+    async def post(self, endpoint: str, *args, raise_for_status: bool = True, **kwargs):
         async with self.session.post(self._url_for(endpoint), *args, **kwargs) as resp:
+            self.maybe_raise_for_status(resp, raise_for_status)
             return await resp.json()
 
-    async def put(self, endpoint: str, *args, **kwargs):
+    async def put(self, endpoint: str, *args, raise_for_status: bool = True, **kwargs):
         async with self.session.put(self._url_for(endpoint), *args, **kwargs) as resp:
+            self.maybe_raise_for_status(resp, raise_for_status)
             return await resp.json()
 
-    async def delete(self, endpoint: str, *args, **kwargs):
+    async def delete(self, endpoint: str, *args, raise_for_status: bool = True, **kwargs):
         async with self.session.delete(self._url_for(endpoint), *args, **kwargs) as resp:
             if resp.status == 204:
                 return None
+
+            self.maybe_raise_for_status(resp, raise_for_status)
             return await resp.json()
diff --git a/bot/cogs/error_handler.py b/bot/cogs/error_handler.py
new file mode 100644
index 000000000..2063df09d
--- /dev/null
+++ b/bot/cogs/error_handler.py
@@ -0,0 +1,92 @@
+import contextlib
+import logging
+
+from discord.ext.commands import (
+    BadArgument,
+    BotMissingPermissions,
+    CommandError,
+    CommandInvokeError,
+    CommandNotFound,
+    NoPrivateMessage,
+    UserInputError,
+)
+from discord.ext.commands import Bot, Context
+
+from bot.api import ResponseCodeError
+
+
+log = logging.getLogger(__name__)
+
+
+class ErrorHandler:
+    """Handles errors emitted from commands."""
+
+    def __init__(self, bot: Bot):
+        self.bot = bot
+
+    async def on_command_error(self, ctx: Context, e: CommandError):
+        command = ctx.command
+        parent = None
+
+        if command is not None:
+            parent = command.parent
+
+        if parent and command:
+            help_command = (self.bot.get_command("help"), parent.name, command.name)
+        elif command:
+            help_command = (self.bot.get_command("help"), command.name)
+        else:
+            help_command = (self.bot.get_command("help"),)
+
+        if hasattr(command, "on_error"):
+            log.debug(f"Command {command} has a local error handler, ignoring.")
+            return
+
+        if isinstance(e, CommandNotFound) and not hasattr(ctx, "invoked_from_error_handler"):
+            tags_get_command = self.bot.get_command("tags get")
+            ctx.invoked_from_error_handler = True
+
+            # Return to not raise the exception
+            with contextlib.suppress(ResponseCodeError):
+                return await ctx.invoke(tags_get_command, tag_name=ctx.invoked_with)
+        elif isinstance(e, BadArgument):
+            await ctx.send(f"Bad argument: {e}\n")
+            await ctx.invoke(*help_command)
+        elif isinstance(e, UserInputError):
+            await ctx.send("Something about your input seems off. Check the arguments:")
+            await ctx.invoke(*help_command)
+        elif isinstance(e, NoPrivateMessage):
+            await ctx.send("Sorry, this command can't be used in a private message!")
+        elif isinstance(e, BotMissingPermissions):
+            await ctx.send(
+                f"Sorry, it looks like I don't have the permissions I need to do that.\n\n"
+                f"Here's what I'm missing: **{e.missing_perms}**"
+            )
+        elif isinstance(e, CommandInvokeError):
+            if isinstance(e.original, ResponseCodeError):
+                if e.original.response.status == 404:
+                    await ctx.send("There does not seem to be anything matching your query.")
+                elif e.original.response.status == 400:
+                    content = await e.original.response.json()
+                    log.debug("API gave bad request on command. Response: %r.", content)
+                    await ctx.send("According to the API, your request is malformed.")
+                elif 500 <= e.original.response.status < 600:
+                    await ctx.send("Sorry, there seems to be an internal issue with the API.")
+                else:
+                    await ctx.send(
+                        "Got an unexpected status code from the "
+                        f"API (`{e.original.response.code}`)."
+                    )
+
+            else:
+                await ctx.send(
+                    f"Sorry, an unexpected error occurred. Please let us know!\n\n```{e}```"
+                )
+                raise e.original
+        else:
+            raise e
+
+
+def setup(bot: Bot):
+    bot.add_cog(ErrorHandler(bot))
+    log.info("Cog loaded: Events")
diff --git a/bot/cogs/sync/cog.py b/bot/cogs/sync/cog.py
index ab591ebf8..222c1668b 100644
--- a/bot/cogs/sync/cog.py
+++ b/bot/cogs/sync/cog.py
@@ -1,12 +1,12 @@
 import logging
 from typing import Callable, Iterable
 
-import aiohttp
 from discord import Guild, Member, Role
 from discord.ext import commands
 from discord.ext.commands import Bot
 
 from bot import constants
+from bot.api import ResponseCodeError
 from bot.cogs.sync import syncers
 
 log = logging.getLogger(__name__)
@@ -94,9 +94,9 @@ class Sync:
             # fields that may have changed since the last time we've seen them.
             await self.bot.api_client.put('bot/users/' + str(member.id), json=packed)
 
-        except aiohttp.client_exceptions.ClientResponseError as e:
+        except ResponseCodeError as e:
             # If we didn't get 404, something else broke - propagate it up.
-            if e.status != 404:
+            if e.response.status != 404:
                 raise
 
             got_error = True  # yikes
@@ -137,8 +137,8 @@ class Sync:
                         'roles': sorted(role.id for role in after.roles)
                     }
                 )
-            except aiohttp.client_exceptions.ClientResponseError as e:
-                if e.status != 404:
+            except ResponseCodeError as e:
+                if e.response.status != 404:
                     raise
 
                 log.warning(
diff --git a/bot/cogs/watchchannels/talentpool.py b/bot/cogs/watchchannels/talentpool.py
index 6fbe2bc03..47d207d05 100644
--- a/bot/cogs/watchchannels/talentpool.py
+++ b/bot/cogs/watchchannels/talentpool.py
@@ -3,10 +3,10 @@ import textwrap
 from collections import ChainMap
 from typing import Union
 
-from aiohttp.client_exceptions import ClientResponseError
 from discord import Color, Embed, Member, User
 from discord.ext.commands import Context, group
 
+from bot.api import ResponseCodeError
 from bot.constants import Channels, Guild, Roles, Webhooks
 from bot.decorators import with_role
 from bot.pagination import LinePaginator
@@ -170,8 +170,8 @@ class TalentPool(WatchChannel):
         """
         try:
             nomination = await self.bot.api_client.get(f"{self.api_endpoint}/{nomination_id}")
-        except ClientResponseError as e:
-            if e.status == 404:
+        except ResponseCodeError as e:
+            if e.response.status == 404:
                 self.log.trace(f"Nomination API 404: Can't nomination with id {nomination_id}")
                 await ctx.send(f":x: Can't find a nomination with id `{nomination_id}`")
                 return
diff --git a/bot/cogs/watchchannels/watchchannel.py b/bot/cogs/watchchannels/watchchannel.py
index fe6d6bb6e..3a24e3f21 100644
--- a/bot/cogs/watchchannels/watchchannel.py
+++ b/bot/cogs/watchchannels/watchchannel.py
@@ -8,11 +8,11 @@ from collections import defaultdict, deque
 from dataclasses import dataclass
 from typing import Optional
 
-import aiohttp
 import discord
 from discord import Color, Embed, Message, Object, errors
 from discord.ext.commands import BadArgument, Bot, Context
 
+from bot.api import ResponseCodeError
 from bot.cogs.modlog import ModLog
 from bot.constants import BigBrother as BigBrotherConfig, Guild as GuildConfig, Icons
 from bot.pagination import LinePaginator
@@ -157,8 +157,8 @@ class WatchChannel(ABC):
         """
         try:
             data = await self.bot.api_client.get(self.api_endpoint, params=self.api_default_params)
-        except aiohttp.ClientResponseError as e:
-            self.log.exception(f"Failed to fetch the watched users from the API", exc_info=e)
+        except ResponseCodeError as err:
+            self.log.exception(f"Failed to fetch the watched users from the API", exc_info=err)
             return False
 
         self.watched_users = defaultdict(dict)