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Fixed Possible bug in Post datawriter...

Liam W

Well-known member
I'm not sure if this would be classed as a bug or not, but I've spent ages trying to figure out what is causing the error and I finally found it so...

This is the _getForumInfo() method in the post datawriter:

protected function _getForumInfo()
        if (!$forum = $this->getExtraData(self::DATA_FORUM))
            $forum = $this->getModelFromCache('XenForo_Model_Forum')->getForumByThreadId($this->get('thread_id'));

            $this->setExtraData(self::DATA_FORUM, $forum ? $forum : array());

        return $this->getExtraData(self::DATA_FORUM);
If the forum extra isn't set, it attempts to get it based on the thread id (which may not actually be set yet, if this is called during preSave of a thread insert and this is the first post dw). If this fails, it sets the forum extra to an empty array.

The issue arises in the setExtraData method:

public function setExtraData($name, $value)
        if ($name == self::DATA_FORUM)
            if (!is_array($value))

        return parent::setExtraData($name, $value);
The set method calls the setForumCacheItem method in the Thread datawriter if the input value is an array. That method in turns uses the node_id key from that value, however as the array is empty (as it couldn't get the forum data), this causes a server error.

Unlikely to happen, yet it happened to me and has taken me ages to figure out. I'll need to add a check to one of my addons...



XenForo developer
Staff member
I think it makes sense to only set the cache if we get a valid response; that will at least prevent an error.

Though I would also note that the usage generally assumes it's being run post save (or at least where a forum is essentially guaranteed to exist).