[wp-trac] [WordPress Trac] #53883: Custom Fields Toggle cannot be turned off

[WordPress Trac]

#53883: Custom Fields Toggle cannot be turned off
--------------------------+-----------------------------
 Reporter:  mreishus      |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Editor        |    Version:  5.8
 Severity:  normal        |   Keywords:
  Focuses:                |
--------------------------+-----------------------------
 == Scope Note

 **This is a coordination problem between WordPress and Gutenberg and
 requires changes on both sides.** I have patches for both that I will be
 submitting shortly.

 == Summary

 When using a plugin to disable Custom Fields in the post editor, WordPress
 attempts to change {{{$editor_settings}}} to tell Gutenberg not to render
 the Custom Fields settings toggle in a preferences modal. However,
 Gutenberg is listening for a value that is impossible to send in PHP, and
 the settings toggle remains visible even when the feature itself is
 disabled.

 == Steps to reproduce

 1. Have a clean WordPress.org installation
 2. Create {{{wp-content/plugins/disable-custom-fields.php}}}
 {{{
 <?php
 /**
  * Plugin Name: Disable Custom Fields
  * Plugin URI: http://www.mywebsite.com/disable-custom-fields
  * Description: Disable Custom Fields
  * Version: 1.0
  * Author: Your Name
  * Author URI: http://www.mywebsite.com
  */

 add_action( 'add_meta_boxes', 'plugin_disable_custom_fields', 1 );

 function plugin_disable_custom_fields() {
     remove_post_type_support( get_post_type(), 'custom-fields' );
 }


 add_action( 'do_meta_boxes', 'plugin_meta_boxes', 10, 2 );

 function plugin_meta_boxes( $page, $context ) {
     remove_meta_box( 'postcustom', get_post_type(), 'normal' );
 }
 }}}
 3. Visit /wp-admin and activate this plugin.
 4. Visit post editor on WordPress.org site. With this plugin enabled,
 [https://github.com/WordPress/WordPress/blob/9a4280c75f7bf76062b61207e3ecdb3a0e0f298e
 /wp-admin/edit-form-blocks.php#L260 this if condition] will always
 trigger, and the
 [https://github.com/WordPress/WordPress/blob/9a4280c75f7bf76062b61207e3ecdb3a0e0f298e
 /wp-admin/edit-form-blocks.php#L261 unset(
 $editor_settings['enableCustomFields'] );] always runs.
 5. Click the three dots menu in the top right.
 6. Click "preferences" at the bottom. Screenshot: [[Image( https://user-
 images.githubusercontent.com/937354/128374126-c22ad772-d02f-4df4-9c4b-
 bb9be3748a71.png )]]
 7. A modal appears. Click panels on the left.
 8. Turn on "Custom Fields".  Screenshot: [[Image( https://user-
 images.githubusercontent.com/937354/128374210-5d7311eb-6073-4ffa-
 8fd5-6754ac3c5aa3.png )]]
 9. See message asking to enable and reload, click the button. Screenshot:
 [[Image( https://user-images.githubusercontent.com/937354/128374223
 -df55a53c-b4ae-4261-b664-b256ee202d28.png )]]
 10. Page reloads
 11. Re-visit the custom fields setting, see that it is turned off.

 Expected to see: The entire "Custom Settings" option does not appear,
 because {{{$editor_settings['enableCustomFields']}}} is unset by this core
 code.

 == Coordination between WordPress and Gutenberg

 * Gutenberg hides the option, but only if {{{enableCustomFields}}} is set
 to {{{undefined}}} in JavaScript.
 [https://github.com/WordPress/gutenberg/blob/333668e7149a1f3f2a39810372ecb11422fe4f7c/packages
 /edit-post/src/components/preferences-modal/meta-boxes-section.js#L57-L58
 Code link 1],
 [https://github.com/WordPress/gutenberg/blob/333668e7149a1f3f2a39810372ecb11422fe4f7c/packages
 /edit-post/src/components/preferences-modal/meta-boxes-section.js#L31-L32
 Code link 2].
 * PHP cannot set {{{$editor_settings['enableCustomFields']}}} equal to
 {{{undefined}}}, because {{{undefined}}} is not a value in PHP. It can set
 to {{{true}}}, {{{false}}}, {{{null}}}, or decline to set the value at
 all, but none of these options work.
   * **{{{true}}}, {{{false}}}, {{{null}}}** - All fail because they are
 not {{{=== undefined}}} in javascript.
   * **Using {{{unset()}}} to not send the value at all** - This is what
 the code currently does. It fails because when gutenberg sees no value is
 sent, it
 [https://github.com/WordPress/gutenberg/blob/333668e7149a1f3f2a39810372ecb11422fe4f7c/packages/editor/src/store/defaults.js#L30
 uses its default settings system to set it to false], which is also not
 {{{=== undefined}}}.
 * Therefore, Gutenberg wants {{{$editor_settings['enableCustomFields'] ===
 undefined}}} in order to hide the toggle, but that value is impossible to
 send.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/53883>
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