Add filter ensuring selectors metadata is available

lib/compat/wordpress-6.3/blocks.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * Temporary compatibility shims for block APIs present in Gutenberg.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Ensure the selectors property, set via block.json metadata, is included
+ * within the block type's settings.
+ *
+ * Note: This should be removed when the minimum required WP version is >= 6.2.
+ *
+ * @see https://github.com/WordPress/gutenberg/pull/46496
+ *
+ * @param array $settings Current block type settings.
+ * @param array $metadata Block metadata as read in via block.json.
+ *
+ * @return array Filtered block type settings.
+ */
+function gutenberg_add_selectors_to_block_type_settings( $settings, $metadata ) {
+	if ( ! isset( $settings['selectors'] ) && isset( $metadata['selectors'] ) ) {
+		$settings['selectors'] = $metadata['selectors'];
+	}
+
+	return $settings;
+}
+add_filter( 'block_type_metadata_settings', 'gutenberg_add_selectors_to_block_type_settings', 10, 2 );

lib/load.php

@@ -102,6 +102,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 
 // WordPress 6.3 compat.
 require __DIR__ . '/compat/wordpress-6.3/html-api/class-gutenberg-html-tag-processor-6-3.php';
+require __DIR__ . '/compat/wordpress-6.3/blocks.php';
 
 // Experimental features.
 remove_action( 'plugins_loaded', '_wp_theme_json_webfonts_handler' ); // Turns off WP 6.0's stopgap handler for Webfonts API.