Navwalker class for Sage 9

walker.php

<?php

namespace App;

/**
 * Class NavWalker
 *
 * Bootstrap 4 walker with cleaner markup for wp_nav_menu()
 * For use with Sage >= 8.5
 *
 * Based on Soil NavWalker
 * @url https://github.com/roots/soil
 *
 *
 * Walker_Nav_Menu (WordPress default) example output:
 *   <li id="menu-item-8" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-8"><a href="/">Home</a></li>
 *
 * NavWalker example output:
 *   <li class="nav-item menu-item menu-home"><a class="nav-link" href="/">Home</a></li>
 *
 * @package Roots\Sage\Nav
 */
class NavWalker extends \Walker_Nav_Menu
{
    /**
     * @var bool
     */
    private $cpt; // Boolean, is current post a custom post type
    /**
     * @var false|string
     */
    private $archive; // Stores the archive page for current URL

    /**
     * NavWalker constructor.
     */
    public function __construct()
    {
        add_filter('nav_menu_css_class', array($this, 'cssClasses'), 10, 2);
        add_filter('nav_menu_item_id', '__return_null');
        $cpt = get_post_type();
        $this->cpt = in_array($cpt, get_post_types(array('_builtin' => false)));
        $this->archive = get_post_type_archive_link($cpt);
    }

    /**
     * Check item classes for current or active
     *
     * @param $classes
     *
     * @return int
     */
    public function checkCurrent($classes)
    {
        return preg_match('/(current[-_])|active/', $classes);
    }

    // @codingStandardsIgnoreStart

    /**
     * Add dropdown menu class to dropdown UL
     *
     * @param string $output
     * @param int $depth
     * @param array $args
     */
    function start_lvl(&$output, $depth = 0, $args = [])
    {
        $output .= "\n<ul class=\"dropdown-menu\" aria-labelledby=\"navbarDropdownMenuLink\">\n";
    }

    /**
     * Add required Bootstrap 4 classes to anchor links.
     *
     * @param string $output
     * @param \WP_Post $item
     * @param int $depth
     * @param array $args
     * @param int $id
     */
    function start_el(&$output, $item, $depth = 0, $args = [], $id = 0)
    {
        $item_html = '';

        parent::start_el($item_html, $item, $depth, $args);

        if ($item->is_subitem) {
            $item_html = str_replace('<a', '<a class="nav-link dropdown-toggle" data-hover="dropdown" aria-haspopup="true" aria-expanded="false"', $item_html);
            $item_html = str_replace('</a>', ' <b class="caret"></b></a>', $item_html);
        } else {
            $item_html = str_replace('<a', '<a class="nav-link"', $item_html);
        }

        $item_html = apply_filters('wp_nav_menu_item', $item_html);

        $output .= $item_html;
    }

    /**
     * Add active classes to active items & sub items
     *
     * @param object $element
     * @param array $children_elements
     * @param int $max_depth
     * @param int $depth
     * @param array $args
     * @param string $output
     */
    public function display_element($element, &$children_elements, $max_depth, $depth = 0, $args, &$output)
    {
        $element->is_subitem = ((!empty($children_elements[$element->ID]) && (($depth + 1) < $max_depth || ($max_depth === 0))));

        if ($element->is_subitem) {
            foreach ($children_elements[$element->ID] as $child) {
                if ($child->current_item_parent || $this->url_compare($this->archive, $child->url)) {
                    $element->classes[] = 'active';
                }
            }
        }

        $element->is_active = (!empty($element->url) && strpos($this->archive, $element->url));

        if ($element->is_active) {
            $element->classes[] = 'active';
        }

        parent::display_element($element, $children_elements, $max_depth, $depth, $args, $output);
    }

    // @codingStandardsIgnoreEnd

    /**
     * Clean up css classes
     *
     * @param $classes
     * @param $item
     *
     * @return array
     */
    public function cssClasses($classes, $item)
    {
        $slug = sanitize_title($item->title);

        // Fix core `active` behavior for custom post types
        if ($this->cpt) {
            $classes = str_replace('current_page_parent', '', $classes);

            if ($this->url_compare($this->archive, $item->url)) {
                $classes[] = 'active';
            }
        }

        // Remove most core classes
        $classes = preg_replace('/(current(-menu-|[-_]page[-_])(item|parent|ancestor))/', 'active', $classes);
        $classes = preg_replace('/^((menu|page)[-_\w+]+)+/', '', $classes);

        // Add `menu-item` class & re-add core `menu-item` class
        $classes[] = 'nav-item menu-item';

        // Add `dropdown` class & re-add core `menu-item-has-children` class on parent elements
        if ($item->is_subitem) {
            $classes[] = 'dropdown menu-item-has-children';
        }

        // Add `menu-<slug>` class
        $classes[] = 'menu-' . $slug;

        $classes = array_unique($classes);
        $classes = array_map('trim', $classes);

        return array_filter($classes);
    }

    /**
     * Make a URL relative
     *
     * Utility function, from soil
     * @url https://github.com/roots/soil
     *
     * @param $input
     *
     * @return string
     */
    public function root_relative_url($input)
    {
        if (is_feed()) {
            return $input;
        }
        $url = parse_url($input);
        if (!isset($url['host']) || !isset($url['path'])) {
            return $input;
        }
        $site_url = parse_url(network_home_url());  // falls back to home_url
        if (!isset($url['scheme'])) {
            $url['scheme'] = $site_url['scheme'];
        }
        $hosts_match = $site_url['host'] === $url['host'];
        $schemes_match = $site_url['scheme'] === $url['scheme'];
        $ports_exist = isset($site_url['port']) && isset($url['port']);
        $ports_match = ($ports_exist) ? $site_url['port'] === $url['port'] : true;
        if ($hosts_match && $schemes_match && $ports_match) {
            return wp_make_link_relative($input);
        }

        return $input;
    }

    /**
     * Compare URL against relative URL
     *
     * Utility function, from Soil
     * @url https://github.com/roots/soil
     *
     * @param $url
     * @param $rel
     *
     * @return bool
     */
    public function url_compare($url, $rel)
    {
        $url = trailingslashit($url);
        $rel = trailingslashit($rel);

        return ((strcasecmp($url, $rel) === 0) || $this->root_relative_url($url) == $rel);
    }

}

/**
 * Clean up wp_nav_menu_args
 *
 * Remove the container
 * Remove the id="" on nav menu items
 *
 * @param string $args
 *
 * @return array
 */
function nav_menu_args($args = '')
{
    $nav_menu_args = [];
    $nav_menu_args['container'] = false;


    if (is_array($args) && !$args['items_wrap']) {
        $nav_menu_args['items_wrap'] = '<ul class="%2$s">%3$s</ul>';
    }

    if (!$args['walker']) {
        $nav_menu_args['walker'] = new NavWalker();
    }


    return array_merge($args, $nav_menu_args);
}

add_filter('wp_nav_menu_args', __NAMESPACE__ . '\\nav_menu_args');
add_filter('nav_menu_item_id', '__return_null');