[wp-trac] [WordPress Trac] #39803: REST API meta type not working properly for custom post types

[WordPress Trac]

#39803: REST API meta type not working properly for custom post types
--------------------------+-----------------------------
 Reporter:  chriseverson  |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  REST API      |    Version:  4.7
 Severity:  normal        |   Keywords:
  Focuses:  rest-api      |
--------------------------+-----------------------------
 When attempting to set meta via a custom post types api endpoint, the meta
 type is always set to `post`. This results in all meta updates for custom
 post types via the REST API failing.

 For example:

 {{{#!php
 $args = [
         'type'         => 'string',
         'single'       => true,
         'show_in_rest' => true
 ];

 register_meta( 'book', 'author', $args );
 }}}

 If I'm understanding correctly, the above should expose the 'author' meta
 to the REST API. However, in the REST API, all of these fail due to a
 check against `WP_REST_Post_Meta_Fields->get_registered_fields()`.

 `WP_REST_Post_Meta_Fields->get_registered_fields()` in turn matches meta
 keys to `get_registered_meta_keys( $this->get_meta_type() )` which always
 returns `post`.

 Not sure if any of that makes sense...

 The fix would be to make `WP_REST_Post_Meta_Fields->get_meta_type()`
 return the post type as far as I can tell.

 I would love to tackle this one, however I wanted to get some input from
 someone more well-versed in the REST API codebase before tackling this to
 be sure that there isn't a reason that
 `WP_REST_Post_Meta_Fields->get_meta_type()` is explicitly set to return
 `post`.

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Ticket URL: <https://core.trac.wordpress.org/ticket/39803>
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