[3.4] Case-Insensitive SelfRole (#3865) (#6061)

Co-authored-by: AA <chasehult@gmail.com>
Co-authored-by: Draper <27962761+Drapersniper@users.noreply.github.com>
Co-authored-by: Flame442 <34169552+Flame442@users.noreply.github.com>

redbot/cogs/admin/converters.py

@@ -1,6 +1,7 @@
 import discord
 from redbot.core import commands
 from redbot.core.i18n import Translator
+from redbot.core.utils import AsyncIter
 
 _ = Translator("AdminConverters", __file__)
 
@@ -11,13 +12,33 @@ class SelfRole(commands.Converter):
         if admin is None:
             raise commands.BadArgument(_("The Admin cog is not loaded."))
 
-        role_converter = commands.RoleConverter()
-        role = await role_converter.convert(ctx, arg)
-
         selfroles = await admin.config.guild(ctx.guild).selfroles()
+        role_converter = commands.RoleConverter()
 
+        pool = set()
+        async for role_id in AsyncIter(selfroles, steps=100):
+            role = ctx.guild.get_role(role_id)
+            if role is None:
+                continue
+            if role.name.casefold() == arg.casefold():
+                pool.add(role)
+
+        if not pool:
+            role = await role_converter.convert(ctx, arg)
             if role.id not in selfroles:
                 raise commands.BadArgument(
-                _('The role "{role_name}" is not a valid selfrole.').format(role_name=role.name)
+                    _('The role "{role_name}" is not a valid selfrole.').format(
+                        role_name=role.name
                     )
+                )
+        elif len(pool) > 1:
+            raise commands.BadArgument(
+                _(
+                    "This selfrole has more than one case insensitive match. "
+                    "Please ask a moderator to resolve the ambiguity, or "
+                    "use the role ID to reference the role."
+                )
+            )
+        else:
+            role = pool.pop()
         return role