src/Debug/Output/File.php
public function onConfig(Event $event)
    {
        $file = $this->debug->getCfg('file');
        $this->setFile($file);
    }
public function onConfig(Event $event)
    {
        $file = $this->debug->getCfg('file');
        $this->setFile($file);
    }
debug.config event subscriber

@param Event $event debug.config event object

@return void