[wp-trac] [WordPress Trac] #17156: Filters to allow setting custom taxonomy on the fly

[WordPress Trac]

#17156: Filters to allow setting custom taxonomy on the fly
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 Reporter:  dougal       |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Taxonomy     |    Version:
 Severity:  normal       |   Keywords:
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 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.

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Ticket URL: <http://core.trac.wordpress.org/ticket/17156>
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