Filters to allow setting custom taxonomy on the fly

[dougal]

I'm currently working on a theme, and one of the things I wanted to do is to automatically set the Post Format when using an XML-RPC client. This isn't currently supported by the WordPress for iPhone app, for example, so I was trying to hack around it by looking for a string at the beginning of a post, something like:

:status: Watching the game and drinking a beer. Life is good.

I was going to detect the ':status:' string, remove it from post_content, update the post on the fly, and set the post format.

But I keep running into roadblocks.

For one thing, in class-wp-xmlrpc-server.php, the mw_newPost() method doesn't do any filtering of the supplied data. This would be the ideal place for me to do what I want, because I could theoretically just add a 'tax_input' key to the post data that is passed into wp_insert_post(), and everything would just be magic from there. I suggest adding a new filter after the data is compacted into the $postdata array, and before it is passed to wp_insert_post();

Similarly, another opportunity would be is if there was a filter in wp_insert_post() after parsing the args, but before the extract() is performed. This would give another chance to inject/alter the post data before it is processed.

Without a filter in one of those places, it's extremely difficult for a plugin or theme to set/change custom taxonomy terms on a post on the fly, when the post comes in via XML-RPC.

So that leaves us with just a couple of other opportunities to act: the 'wp_insert_post_data' filter, and the 'wp_insert_post' action. With the filter, I can detect my sentinel string and strip it back out of the post, but I can't set the post_format, because we don't have a post_ID yet. But if we get all the way to the 'wp_insert_post' action, updating the post content to strip out the sentinel is a problem, because using wp_update_post() will in turn call wp_insert_post(), which is a recursive loop.

One more place where a filter would be useful is when wp_insert_post() checks for the $tax_input variable (which would have been included in the original $postarr argument passed into the function). A 'tax_input' filter which received the post_ID would be another chance to extend the ability to manipulate custom taxonomies on the fly, at post creation time.

[markoheijnen]

I believe this can be closed now due the work in 3.4 where you now can add terms and there are some extra hooks added

[dougal]

Are you sure? I just took a quick glance through the xmlrpc code and post.php, and I don't see any new places to hook a filter for what I've described. I also did a diff of the 3.3 and 3.4 versions of post.php, and nothing jumped out at me.

[markoheijnen]

Only the wp.* methods should be used now. In 3.4 we added wp.newPost and that can handle taxonomies by names or id's.
It uses the function _insert_post inside the XML-RPC class. This has a filter "xmlrpc_wp_insert_post_data" what filters the data before it get passed in.

I'm not sure if this is what you wanted or not. Please let me know.