Add support for trailing space in prefix

CHANGELOG.md

@@ -22,6 +22,7 @@ however, insignificant breaking changes do not guarantee a major version bump, s
 - Added custom database name detection in `CONNECTION_URI`
 - Added dpy and python version info in `?about` embed and credit for contributors
 - New config option: `mention_message`, this will include an additional configurable message next to role mention on thread creation. Defaults to None.
+- Support for trailing space in `?prefix` command, `?prefix "mm "
 
 ### Changed
 - Guild icons in embed footers and author urls now have a fixed size of 128. ([PR #3261](https://github.com/modmail-dev/modmail/pull/3261))

cogs/utility.py

@@ -785,17 +785,23 @@ async def prefix(self, ctx, *, prefix=None):
         Change the prefix of the bot.
 
         Type only `{prefix}prefix` to retrieve your current bot prefix.
+        Enclose your prefix in doublequotes to include trailing spaces.
+
+        Example: `{prefix}prefix "mm "`
         """
 
         current = self.bot.prefix
-        embed = discord.Embed(title="Current prefix", color=self.bot.main_color, description=f"{current}")
+        embed = discord.Embed(title="Current prefix", color=self.bot.main_color, description=f"`{current}`")
 
         if prefix is None:
             await ctx.send(embed=embed)
         else:
+            pattern = r'"([^"]{1,19})"'
+            match = re.search(pattern, prefix)
+
             embed.title = "Changed prefix!"
-            embed.description = f"Set prefix to `{prefix}`"
-            self.bot.config["prefix"] = prefix
+            embed.description = f"Set prefix to `{match.group(1) if match else prefix}`"
+            self.bot.config["prefix"] = match.group(1) if match else prefix
             await self.bot.config.update()
             await ctx.send(embed=embed)