Create a UserMentionOrID converter.

When we're using the !reply command, using a regular UserConverter is
somewhat problematic. For example, if I wanted to send the message
"lemon loves you", then I'd try to write `!reply lemon loves you` -
however, the optional User converter would then try to convert `lemon`
into a User, which it would successfully do since there's like 60 lemons
on our server.

As a result, the message "loves you" would be sent to a user called
lemon.. god knows which one.

To solve this bit of ambiguity, I introduce a new converter which only
converts user mentions or user IDs into User, not strings that may be
intended as part of the message you are sending.

https://github.com/python-discord/bot/issues/1041

2 files changed, 24 insertions, 1 deletions

diff --git a/bot/cogs/dm_relay.py b/bot/cogs/dm_relay.py
index 0c3eddf42..c5a3dba22 100644
--- a/bot/cogs/dm_relay.py
+++ b/bot/cogs/dm_relay.py
@@ -8,6 +8,7 @@ from discord.ext.commands import Cog
 
 from bot import constants
 from bot.bot import Bot
+from bot.converters import UserMentionOrID
 from bot.utils import RedisCache
 from bot.utils.checks import in_whitelist_check, with_role_check
 from bot.utils.messages import send_attachments
@@ -29,7 +30,7 @@ class DMRelay(Cog):
         self.bot.loop.create_task(self.fetch_webhook())
 
     @commands.command(aliases=("reply",))
-    async def send_dm(self, ctx: commands.Context, member: Optional[discord.Member], *, message: str) -> None:
+    async def send_dm(self, ctx: commands.Context, member: Optional[UserMentionOrID], *, message: str) -> None:
         """
         Allows you to send a DM to a user from the bot.
 
diff --git a/bot/converters.py b/bot/converters.py
index 898822165..7c62f92dd 100644
--- a/bot/converters.py
+++ b/bot/converters.py
@@ -330,6 +330,28 @@ def proxy_user(user_id: str) -> discord.Object:
     return user
 
 
+class UserMentionOrID(UserConverter):
+    """
+    Converts to a `discord.User`, but only if a mention or userID is provided.
+
+    Unlike the default `UserConverter`, it does allow conversion from name, or name#descrim.
+
+    This is useful in cases where that lookup strategy would lead to ambiguity.
+    """
+
+    async def convert(self, ctx: Context, argument: str) -> discord.User:
+        """Convert the `arg` to a `discord.User`."""
+        print(argument)
+        match = self._get_id_match(argument) or re.match(r'<@!?([0-9]+)>$', argument)
+
+        print(match)
+
+        if match is not None:
+            return await super().convert(ctx, argument)
+        else:
+            raise BadArgument(f"`{argument}` is not a User mention or a User ID.")
+
+
 class FetchedUser(UserConverter):
     """
     Converts to a `discord.User` or, if it fails, a `discord.Object`.