diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/class-walker-nav-menu.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-walker-nav-menu.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,264 @@
+<?php
+/**
+ * Nav Menu API: Walker_Nav_Menu class
+ *
+ * @package WordPress
+ * @subpackage Nav_Menus
+ * @since 4.6.0
+ */
+
+/**
+ * Core class used to implement an HTML list of nav menu items.
+ *
+ * @since 3.0.0
+ *
+ * @see Walker
+ */
+class Walker_Nav_Menu extends Walker {
+	/**
+	 * What the class handles.
+	 *
+	 * @since 3.0.0
+	 * @var string
+	 *
+	 * @see Walker::$tree_type
+	 */
+	public $tree_type = array( 'post_type', 'taxonomy', 'custom' );
+
+	/**
+	 * Database fields to use.
+	 *
+	 * @since 3.0.0
+	 * @todo Decouple this.
+	 * @var array
+	 *
+	 * @see Walker::$db_fields
+	 */
+	public $db_fields = array( 'parent' => 'menu_item_parent', 'id' => 'db_id' );
+
+	/**
+	 * Starts the list before the elements are added.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @see Walker::start_lvl()
+	 *
+	 * @param string   $output Used to append additional content (passed by reference).
+	 * @param int      $depth  Depth of menu item. Used for padding.
+	 * @param stdClass $args   An object of wp_nav_menu() arguments.
+	 */
+	public function start_lvl( &$output, $depth = 0, $args = array() ) {
+		if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
+			$t = '';
+			$n = '';
+		} else {
+			$t = "\t";
+			$n = "\n";
+		}
+		$indent = str_repeat( $t, $depth );
+
+		// Default class.
+		$classes = array( 'sub-menu' );
+
+		/**
+		 * Filters the CSS class(es) applied to a menu list element.
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array    $classes The CSS classes that are applied to the menu `<ul>` element.
+		 * @param stdClass $args    An object of `wp_nav_menu()` arguments.
+		 * @param int      $depth   Depth of menu item. Used for padding.
+		 */
+		$class_names = join( ' ', apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth ) );
+		$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
+
+		$output .= "{$n}{$indent}<ul$class_names>{$n}";
+	}
+
+	/**
+	 * Ends the list of after the elements are added.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @see Walker::end_lvl()
+	 *
+	 * @param string   $output Used to append additional content (passed by reference).
+	 * @param int      $depth  Depth of menu item. Used for padding.
+	 * @param stdClass $args   An object of wp_nav_menu() arguments.
+	 */
+	public function end_lvl( &$output, $depth = 0, $args = array() ) {
+		if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
+			$t = '';
+			$n = '';
+		} else {
+			$t = "\t";
+			$n = "\n";
+		}
+		$indent = str_repeat( $t, $depth );
+		$output .= "$indent</ul>{$n}";
+	}
+
+	/**
+	 * Starts the element output.
+	 *
+	 * @since 3.0.0
+	 * @since 4.4.0 The {@see 'nav_menu_item_args'} filter was added.
+	 *
+	 * @see Walker::start_el()
+	 *
+	 * @param string   $output Used to append additional content (passed by reference).
+	 * @param WP_Post  $item   Menu item data object.
+	 * @param int      $depth  Depth of menu item. Used for padding.
+	 * @param stdClass $args   An object of wp_nav_menu() arguments.
+	 * @param int      $id     Current item ID.
+	 */
+	public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
+		if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
+			$t = '';
+			$n = '';
+		} else {
+			$t = "\t";
+			$n = "\n";
+		}
+		$indent = ( $depth ) ? str_repeat( $t, $depth ) : '';
+
+		$classes = empty( $item->classes ) ? array() : (array) $item->classes;
+		$classes[] = 'menu-item-' . $item->ID;
+
+		/**
+		 * Filters the arguments for a single nav menu item.
+		 *
+		 * @since 4.4.0
+		 *
+		 * @param stdClass $args  An object of wp_nav_menu() arguments.
+		 * @param WP_Post  $item  Menu item data object.
+		 * @param int      $depth Depth of menu item. Used for padding.
+		 */
+		$args = apply_filters( 'nav_menu_item_args', $args, $item, $depth );
+
+		/**
+		 * Filters the CSS class(es) applied to a menu item's list item element.
+		 *
+		 * @since 3.0.0
+		 * @since 4.1.0 The `$depth` parameter was added.
+		 *
+		 * @param array    $classes The CSS classes that are applied to the menu item's `<li>` element.
+		 * @param WP_Post  $item    The current menu item.
+		 * @param stdClass $args    An object of wp_nav_menu() arguments.
+		 * @param int      $depth   Depth of menu item. Used for padding.
+		 */
+		$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args, $depth ) );
+		$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
+
+		/**
+		 * Filters the ID applied to a menu item's list item element.
+		 *
+		 * @since 3.0.1
+		 * @since 4.1.0 The `$depth` parameter was added.
+		 *
+		 * @param string   $menu_id The ID that is applied to the menu item's `<li>` element.
+		 * @param WP_Post  $item    The current menu item.
+		 * @param stdClass $args    An object of wp_nav_menu() arguments.
+		 * @param int      $depth   Depth of menu item. Used for padding.
+		 */
+		$id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args, $depth );
+		$id = $id ? ' id="' . esc_attr( $id ) . '"' : '';
+
+		$output .= $indent . '<li' . $id . $class_names .'>';
+
+		$atts = array();
+		$atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';
+		$atts['target'] = ! empty( $item->target )     ? $item->target     : '';
+		$atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';
+		$atts['href']   = ! empty( $item->url )        ? $item->url        : '';
+
+		/**
+		 * Filters the HTML attributes applied to a menu item's anchor element.
+		 *
+		 * @since 3.6.0
+		 * @since 4.1.0 The `$depth` parameter was added.
+		 *
+		 * @param array $atts {
+		 *     The HTML attributes applied to the menu item's `<a>` element, empty strings are ignored.
+		 *
+		 *     @type string $title  Title attribute.
+		 *     @type string $target Target attribute.
+		 *     @type string $rel    The rel attribute.
+		 *     @type string $href   The href attribute.
+		 * }
+		 * @param WP_Post  $item  The current menu item.
+		 * @param stdClass $args  An object of wp_nav_menu() arguments.
+		 * @param int      $depth Depth of menu item. Used for padding.
+		 */
+		$atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args, $depth );
+
+		$attributes = '';
+		foreach ( $atts as $attr => $value ) {
+			if ( ! empty( $value ) ) {
+				$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
+				$attributes .= ' ' . $attr . '="' . $value . '"';
+			}
+		}
+
+		/** This filter is documented in wp-includes/post-template.php */
+		$title = apply_filters( 'the_title', $item->title, $item->ID );
+
+		/**
+		 * Filters a menu item's title.
+		 *
+		 * @since 4.4.0
+		 *
+		 * @param string   $title The menu item's title.
+		 * @param WP_Post  $item  The current menu item.
+		 * @param stdClass $args  An object of wp_nav_menu() arguments.
+		 * @param int      $depth Depth of menu item. Used for padding.
+		 */
+		$title = apply_filters( 'nav_menu_item_title', $title, $item, $args, $depth );
+
+		$item_output = $args->before;
+		$item_output .= '<a'. $attributes .'>';
+		$item_output .= $args->link_before . $title . $args->link_after;
+		$item_output .= '</a>';
+		$item_output .= $args->after;
+
+		/**
+		 * Filters a menu item's starting output.
+		 *
+		 * The menu item's starting output only includes `$args->before`, the opening `<a>`,
+		 * the menu item's title, the closing `</a>`, and `$args->after`. Currently, there is
+		 * no filter for modifying the opening and closing `<li>` for a menu item.
+		 *
+		 * @since 3.0.0
+		 *
+		 * @param string   $item_output The menu item's starting HTML output.
+		 * @param WP_Post  $item        Menu item data object.
+		 * @param int      $depth       Depth of menu item. Used for padding.
+		 * @param stdClass $args        An object of wp_nav_menu() arguments.
+		 */
+		$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
+	}
+
+	/**
+	 * Ends the element output, if needed.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @see Walker::end_el()
+	 *
+	 * @param string   $output Used to append additional content (passed by reference).
+	 * @param WP_Post  $item   Page data object. Not used.
+	 * @param int      $depth  Depth of page. Not Used.
+	 * @param stdClass $args   An object of wp_nav_menu() arguments.
+	 */
+	public function end_el( &$output, $item, $depth = 0, $args = array() ) {
+		if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
+			$t = '';
+			$n = '';
+		} else {
+			$t = "\t";
+			$n = "\n";
+		}
+		$output .= "</li>{$n}";
+	}
+
+} // Walker_Nav_Menu