Prevent / being used in bot or server prefixes (#5693)

* Update `[p]set prefix`/`[p]set serverprefix`

* Update cli

* style

* update __main__

* style

* improve checks

* Raise in Red.set_prefixes, update responses

* uniform responses

* Fixes

* Keep generator variable names consistent across files

redbot/__main__.py

@@ -138,6 +138,11 @@ async def _edit_prefix(red, prefix, no_prompt):
             if not prefixes:
                 print("You need to pass at least one prefix!")
                 continue
+            if any(prefix.startswith("/") for prefix in prefixes):
+                print(
+                    "Prefixes cannot start with '/', as it conflicts with Discord's slash commands."
+                )
+                continue
             prefixes = sorted(prefixes, reverse=True)
             await red._config.prefix.set(prefixes)
             print("Prefixes updated.\n")

redbot/core/cli.py

@@ -70,6 +70,11 @@ async def interactive_config(red, token_set, prefix_set, *, print_header=True):
             if len(prefix) > 10:
                 if not confirm("Your prefix seems overly long. Are you sure that it's correct?"):
                     prefix = ""
+            if prefix.startswith("/"):
+                print(
+                    "Prefixes cannot start with '/', as it conflicts with Discord's slash commands."
+                )
+                prefix = ""
             if prefix:
                 await red._config.prefix.set([prefix])
 

redbot/core/core_commands.py

@@ -3536,6 +3536,11 @@ class Core(commands.commands._RuleDropper, commands.Cog, CoreLogic):
         **Arguments:**
             - `<prefixes...>` - The prefixes the bot will respond to globally.
         """
+        if any(prefix.startswith("/") for prefix in prefixes):
+            await ctx.send(
+                _("Prefixes cannot start with '/', as it conflicts with Discord's slash commands.")
+            )
+            return
         if any(len(x) > MAX_PREFIX_LENGTH for x in prefixes):
             await ctx.send(
                 _(
@@ -3584,6 +3589,11 @@ class Core(commands.commands._RuleDropper, commands.Cog, CoreLogic):
             await ctx.bot.set_prefixes(guild=ctx.guild, prefixes=[])
             await ctx.send(_("Server prefixes have been reset."))
             return
+        if any(prefix.startswith("/") for prefix in prefixes):
+            await ctx.send(
+                _("Prefixes cannot start with '/', as it conflicts with Discord's slash commands.")
+            )
+            return
         if any(len(x) > MAX_PREFIX_LENGTH for x in prefixes):
             await ctx.send(_("You cannot have a prefix longer than 25 characters."))
             return

redbot/core/settings_caches.py

@@ -45,6 +45,10 @@ class PrefixManager:
         prefixes = prefixes or []
         if not isinstance(prefixes, list) and not all(isinstance(pfx, str) for pfx in prefixes):
             raise TypeError("Prefixes must be a list of strings")
+        if any(prefix.startswith("/") for prefix in prefixes):
+            raise ValueError(
+                "Prefixes cannot start with '/', as it conflicts with Discord's slash commands."
+            )
         prefixes = sorted(prefixes, reverse=True)
         if gid is None:
             if not prefixes: