Make `FetchedUser` return a `discord.Object` if user *may* exist

The FetchedUser Converter now counts with a `proxy_user` helper function (which
SHOULD NOT be there) to return a user as a last resource, in case
there was an issue fetching from the Discord API, as long as the error
isn't that there's no user with the given ID.

1 files changed, 35 insertions, 7 deletions

diff --git a/bot/converters.py b/bot/converters.py
index fbe9ecd90..b33229cc7 100644
--- a/bot/converters.py
+++ b/bot/converters.py
@@ -281,22 +281,50 @@ class ISODateTime(Converter):
 
 
 class FetchedUser(Converter):
-    """Fetches from the Discord API and returns a `discord.User` object."""
+    """
+    Fetches from the Discord API and returns a `discord.User` or `discord.Object` object, given an ID.
+
+    If the fetching is successful, a `discord.User` object is returned. If it fails and
+    the error doesn't imply the user doesn't exist, then a `discord.Object` is returned
+    via the `user_proxy` function.
+    """
+
+    # XXX: `proxy_user` shouldn't be here as a helper.
+    #  Should wait for PR #651 to import from bot.utils.whatever, maybe?
+    @staticmethod
+    def proxy_user(user_id: str) -> discord.Object:
+        """
+        Create a proxy user object from the given id.
+
+        Used when a Member or User object cannot be resolved.
+        """
+        log.trace(f"Attempting to create a proxy user for the user id {user_id}.")
+
+        try:
+            user_id = int(user_id)
+        except ValueError:
+            raise BadArgument
+
+        user = discord.Object(user_id)
+        user.mention = user.id
+        user.avatar_url_as = lambda static_format: None
+
+        return user
 
     @staticmethod
-    async def convert(ctx: Context, user_id: str) -> discord.User:
-        """Converts `user_id` to a `discord.User` object, after fetching from the Discord API."""
-        # TODO: add docstring
-        # TODO: add remaining exceptions
+    async def convert(ctx: Context, user_id: str) -> t.Union[discord.User, discord.Object]:
+        """Convert `user_id` to a `discord.User` object, after fetching from the Discord API."""
         try:
             user_id = int(user_id)
             user = await ctx.bot.fetch_user(user_id)
         except ValueError:
             raise BadArgument(f"The provided argument can't be turned into integer: `{user_id}`")
         except discord.HTTPException as e:
-            # If the Discord error isn't Unknown user, save it in the log
+            # If the Discord error isn't `Unknown user`, save it in the log and return a proxy
             if e.code != 10013:
-                log.warning(f"Failed to fetch user:")
+                log.warning("Failed to fetch user, returning a proxy instead.")
+                # XXX:
+                return FetchedUser.proxy_user(user_id)
             raise BadArgument
 
         return user