Merge pull request #21703 from Yoast/fix-editor-assets-enqueue

Make sure assets are also enqueued for non block editor editors.

admin/metabox/class-metabox.php

@@ -74,7 +74,11 @@ public function __construct() {
 		}
 
 		add_action( 'add_meta_boxes', [ $this, 'add_meta_box' ] );
-		add_action( 'enqueue_block_assets', [ $this, 'enqueue' ] );
+		// Enqueue metabox assets for the block editor.
+		add_action( 'enqueue_block_editor_assets', [ $this, 'enqueue' ] );
+		// Enqueue metabox assets for other editors.
+		add_action( 'admin_enqueue_scripts', [ $this, 'maybe_enqueue_assets_non_block_editor' ] );
+
 		add_action( 'admin_enqueue_scripts', [ $this, 'enqueue_post_overview_assets' ] );
 		add_action( 'wp_insert_post', [ $this, 'save_postdata' ] );
 		add_action( 'edit_attachment', [ $this, 'save_postdata' ] );
@@ -816,24 +820,35 @@ public function enqueue_post_overview_assets() {
 	}
 
 	/**
-	 * Enqueues all the needed JS and CSS.
-	 *
-	 * @todo [JRF => whomever] Create css/metabox-mp6.css file and add it to the below allowed colors array when done.
+	 * Checks to make sure the current editor used is not the block editor to enqueue all needed assets.
+	 * If it is the block editor the assets are already enqueued in the `enqueue_block_assets` action.
 	 *
 	 * @return void
 	 */
-	public function enqueue() {
+	public function maybe_enqueue_assets_non_block_editor() {
 		global $pagenow;
 
-		$asset_manager = new WPSEO_Admin_Asset_Manager();
+		if ( ( self::is_post_edit( $pagenow ) === false && apply_filters( 'wpseo_always_register_metaboxes_on_admin', false ) === false ) || WP_Screen::get()->is_block_editor() ) {
+			return;
+		}
 
-		$is_editor = self::is_post_overview( $pagenow ) || self::is_post_edit( $pagenow );
+		$this->enqueue();
+	}
 
-		/* Filter 'wpseo_always_register_metaboxes_on_admin' documented in wpseo-main.php */
-		if ( ( $is_editor === false && apply_filters( 'wpseo_always_register_metaboxes_on_admin', false ) === false ) || $this->display_metabox() === false ) {
+	/**
+	 * Enqueues all the needed JS and CSS.
+	 *
+	 * @todo [JRF => whomever] Create css/metabox-mp6.css file and add it to the below allowed colors array when done.
+	 *
+	 * @return void
+	 */
+	public function enqueue() {
+		if ( $this->display_metabox() === false ) {
 			return;
 		}
 
+		$asset_manager = new WPSEO_Admin_Asset_Manager();
+
 		$post_id = get_queried_object_id();
 		// phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Reason: We are not processing form information.
 		if ( empty( $post_id ) && isset( $_GET['post'] ) && is_string( $_GET['post'] ) ) {