From 8d731a12baaf569d170eabe4f90d14e2ec6922af Mon Sep 17 00:00:00 2001
From: Jorge Costa <jorge.costa@developer.pt>
Date: Thu, 1 Feb 2024 14:04:13 +0000
Subject: [PATCH] Add: Footnotes support in core.

---
 src/wp-includes/blocks/footnotes.php   | 21 ----------------
 src/wp-includes/class-wp-post-type.php |  3 +++
 src/wp-includes/default-filters.php    |  3 +++
 src/wp-includes/post.php               | 35 ++++++++++++++++++++++++++
 4 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/src/wp-includes/blocks/footnotes.php b/src/wp-includes/blocks/footnotes.php
index 0cd2ad73ef3d4..dd76bf75bc47b 100644
--- a/src/wp-includes/blocks/footnotes.php
+++ b/src/wp-includes/blocks/footnotes.php
@@ -68,27 +68,6 @@ function render_block_core_footnotes( $attributes, $content, $block ) {
  * @since 6.3.0
  */
 function register_block_core_footnotes() {
-	$post_types = get_post_types(
-		array(
-			'show_in_rest' => true,
-			'public'       => true,
-		)
-	);
-	foreach ( $post_types as $post_type ) {
-		// Only register the meta field if the post type supports the editor, custom fields, and revisions.
-		if ( post_type_supports( $post_type, 'editor' ) && post_type_supports( $post_type, 'custom-fields' ) && post_type_supports( $post_type, 'revisions' ) ) {
-			register_post_meta(
-				$post_type,
-				'footnotes',
-				array(
-					'show_in_rest'      => true,
-					'single'            => true,
-					'type'              => 'string',
-					'revisions_enabled' => true,
-				)
-			);
-		}
-	}
 	register_block_type_from_metadata(
 		__DIR__ . '/footnotes',
 		array(
diff --git a/src/wp-includes/class-wp-post-type.php b/src/wp-includes/class-wp-post-type.php
index 7a2769ed88327..3e291d86b473b 100644
--- a/src/wp-includes/class-wp-post-type.php
+++ b/src/wp-includes/class-wp-post-type.php
@@ -669,6 +669,9 @@ public function add_supports() {
 					add_post_type_support( $this->name, $args );
 				}
 			}
+			if ( post_type_supports( $this->name, 'editor' ) && post_type_supports( $this->name, 'custom-fields' ) && post_type_supports( $this->name, 'revisions' ) && ! post_type_supports( $this->name, 'footnotes' ) ) {
+				add_post_type_support( $this->name, 'footnotes' );
+			}
 			unset( $this->supports );
 		} elseif ( false !== $this->supports ) {
 			// Add default features.
diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 7ebc3a1d3bfe1..58779dd133d97 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -734,6 +734,9 @@
 // CPT wp_block custom postmeta field.
 add_action( 'init', 'wp_create_initial_post_meta' );
 
+// Registers the footnotes meta field for post types that support it.
+add_action( 'init', '_wp_register_footnotes_meta_field', 100 );
+
 // Include revisioned meta when considering whether a post revision has changed.
 add_filter( 'wp_save_post_revision_post_has_changed', 'wp_check_revisioned_meta_fields_have_changed', 10, 3 );
 
diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 69a63625524d1..2501bc9c290d9 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -8150,3 +8150,38 @@ function wp_create_initial_post_meta() {
 		)
 	);
 }
+
+/**
+ * Registers the footnotes meta field for post types that support it.
+ *
+ * @internal
+ * @since 6.5.0
+ *
+ * @link https://github.com/WordPress/gutenberg/pull/57353
+ */
+function _wp_register_footnotes_meta_field() {
+	$post_types = get_post_types(
+		array(
+			'show_in_rest' => true,
+			'public'       => true,
+		)
+	);
+	foreach ( $post_types as $post_type ) {
+		// Only register the meta field if the post type supports the editor, custom fields, and revisions.
+		if ( post_type_supports( $post_type, 'editor' ) && post_type_supports( $post_type, 'custom-fields' ) && post_type_supports( $post_type, 'revisions' ) && post_type_supports( $post_type, 'footnotes' ) ) {
+			$post_type_meta_keys = get_registered_meta_keys( 'post', $post_type );
+			if ( ! isset( $post_type_meta_keys['footnotes'] ) ) {
+				register_post_meta(
+					$post_type,
+					'footnotes',
+					array(
+						'show_in_rest'      => true,
+						'single'            => true,
+						'type'              => 'string',
+						'revisions_enabled' => true,
+					)
+				);
+			}
+		}
+	}
+}