Enforce channel display name limits on slash command (#7309)

app/command_channel_rename.go

@@ -53,6 +53,10 @@ func (me *RenameProvider) DoCommand(args *model.CommandArgs, message string) *mo
 
 	if len(message) == 0 {
 		return &model.CommandResponse{Text: args.T("api.command_channel_rename.message.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	} else if len(message) > model.CHANNEL_NAME_UI_MAX_LENGTH {
+		return &model.CommandResponse{Text: args.T("api.command_channel_rename.too_long.app_error", map[string]interface{}{"Length": len(message)}), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	} else if len(message) < model.CHANNEL_NAME_MIN_LENGTH {
+		return &model.CommandResponse{Text: args.T("api.command_channel_rename.too_short.app_error", map[string]interface{}{"Length": len(message)}), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
 	}
 
 	patch := &model.ChannelPatch{