Block Editor: Unable to enable Custom Fields due to out-of-order merges

[dd32]

After switching WordPress.org from /branches/5.0 to /trunk it appears that we lost the ability to enable Custom Fields.

Upon ​digging into it(slack) I've realised that two merge commits were done in such a way that a later merge commit brought over an older commit that had been covered by an earlier merge, specifically:

• [44244] merged in [43885/branches/5.0/src/wp-admin/includes/meta-boxes.php]
• [44260] merged in [43861/branches/5.0/src/wp-admin/includes/meta-boxes.php] which overwrite the newer commit above

[pento]

46028.diff​ fixes it issue for me.

@dd32, how does this look to you?

[dd32]

Visual check of 46028.diff​ looks correct.

Testing on WordPress.org seems right, The option to select Custom Fields is now present within the editor.

Testing on WordPress.org and removing the metabox using the ​remove_meta_box() example in a mu-plugin has the intended effect of no longer being able to select again.

Looks good to me @pento

[pento]

In 44648:

Block Editor: Restore the Custom Fields display option.

When merging, [44244] and [44260] were committed to trunk the opposite way that they were committed to the 5.0 branch. They were originally committed in [43885] and [43861], respectively.

Due to this switch, a change in how the Custom Fields meta box was registered wasn't merged from the 5.0 branch, causing it to not be registered correctly in trunk.

Props dd32, pento.
Fixes #46028.