[wp-trac] [WordPress Trac] #54484: REST API returns (empty) array for Meta but Schema has type object

[WordPress Trac]

#54484: REST API returns (empty) array for Meta but Schema has type object
-----------------------------------------+-----------------------
 Reporter:  dtrunk90                     |       Owner:  flixos90
     Type:  defect (bug)                 |      Status:  assigned
 Priority:  normal                       |   Milestone:  7.0
Component:  REST API                     |     Version:  4.7
 Severity:  normal                       |  Resolution:
 Keywords:  has-patch changes-requested  |     Focuses:
-----------------------------------------+-----------------------

Comment (by sajib1223):

 == Patch Testing Report

 Patch Tested: https://github.com/WordPress/wordpress-develop/pull/10889

 === Environment
 - WordPress: 7.0-beta1-61709-src
 - PHP: 8.2.29
 - Server: nginx/1.29.5
 - Database: mysqli (Server: 8.4.8 / Client: mysqlnd 8.2.29)
 - Browser: Firefox 148.0
 - OS: Windows 10/11
 - Theme: Twenty Twenty-Five 1.4
 - MU Plugins:
 - test-trac-54484.php
 - Plugins:
 - Test Reports 1.2.1

 === Steps taken
 1. Applied the PR diff on trunk using gh pr diff 10889 | git apply
 2. Created an MU plugin that registers a custom post type book with
 show_in_rest => true and custom-fields support, but no registered meta
 fields
 3. Created a sample book post (ID 7) via WP-CLI
 4. Tested http://localhost:8889/wp-json/wp/v2/books/7?_fields=meta with
 patch — returned {"meta":{}} (empty object)
 5. Reverted the patch using git checkout
 6. Tested the same URL without patch — returned {"meta":[]} (empty array,
 the bug)
 7. Re-applied the patch and ran PHPUnit tests:
 WP_Test_REST_Post_Meta_Fields (151 tests, 581 assertions),
 WP_Test_REST_Posts_Controller (278 tests, 2627 assertions), REST_Blocks
 (17 tests, 26 assertions) — all passing
 8. ✅ Patch is solving the problem

 === Expected result
 - Empty meta field should return {} (JSON object) instead of [] (JSON
 array), matching the REST API schema type definition of object

 === Additional Notes
 - Default posts/pages have Gutenberg's footnotes meta registered, so their
 meta is never truly empty. A custom post type with no registered meta is
 needed to reproduce the bug.
 - The patch also correctly handles the wp_pattern_sync_status meta in the
 blocks controller for both array and object
 types.


 === Support Content

 MU Plugin used for testing (mu-plugins/test-trac-54484.php):

 {{{#!php
 <?php
 add_action( 'init', function () {
     register_post_type(
         'book',
         array(
             'label'        => 'Books',
             'public'       => true,
             'show_in_rest' => true,
             'rest_base'    => 'books',
             'supports'     => array( 'title', 'editor', 'custom-fields' ),
         )
     );
 });
 }}}

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/54484#comment:12>
WordPress Trac <https://core.trac.wordpress.org/>
WordPress publishing platform