Back Compat: Add Patterns submenu for WordPress 6.4 (#60804)

Co-authored-by: t-hamano <[email protected]>
Co-authored-by: aaronrobertshaw <[email protected]>
Co-authored-by: youknowriad <[email protected]>

lib/compat/wordpress-6.5/compat.php

@@ -51,3 +51,42 @@ function gutenberg_add_use_customizer_site_logo_url_flag() {
 }
 
 add_action( 'admin_init', 'gutenberg_add_use_customizer_site_logo_url_flag' );
+
+/**
+ * Add a Patterns submenu (wp-admin/edit.php?post_type=wp_block) under the Appearance menu
+ * for the Classic theme. This function should not be backported to core, and should be
+ * removed when the required WP core version for Gutenberg is >= 6.5.0.
+ *
+ * @global array $submenu
+ */
+function gutenberg_add_patterns_page_submenu_item() {
+	if ( ! is_wp_version_compatible( '6.5' ) && ! wp_is_block_theme() ) {
+		// Move the Themes submenu forward and inject a Patterns submenu.
+		global $submenu;
+		$submenu['themes.php'][4] = $submenu['themes.php'][5];
+		$submenu['themes.php'][5] = array( __( 'Patterns', 'gutenberg' ), 'edit_theme_options', 'edit.php?post_type=wp_block' );
+		ksort( $submenu['themes.php'], SORT_NUMERIC );
+	}
+}
+add_action( 'admin_init', 'gutenberg_add_patterns_page_submenu_item' );
+
+/**
+ * Filter the `wp_die_handler` to allow access to the Site Editor's Patterns page
+ * (wp-admin/site-editor.php?path=%2Fpatterns) internally for the Classic theme. This
+ * function should not be backported to core, and should be removed when the required
+ * WP core version for Gutenberg is >= 6.5.0.
+ *
+ * @param callable $default_handler The default handler.
+ * @return callable The default handler or a custom handler.
+ */
+function gutenberg_patterns_page_wp_die_handler( $default_handler ) {
+	if ( ! is_wp_version_compatible( '6.5' ) && ! wp_is_block_theme() && str_contains( $_SERVER['REQUEST_URI'], 'site-editor.php' ) ) {
+		$is_patterns      = isset( $_GET['postType'] ) && 'wp_block' === sanitize_key( $_GET['postType'] );
+		$is_patterns_path = isset( $_GET['path'] ) && 'patterns' === sanitize_key( $_GET['path'] );
+		if ( $is_patterns || $is_patterns_path ) {
+			return '__return_false';
+		}
+	}
+	return $default_handler;
+}
+add_filter( 'wp_die_handler', 'gutenberg_patterns_page_wp_die_handler' );