Woocommerce: list all products without a shipping class

Information originally found here: https://shanegowland.com/advanced-woocommerce/2018/how-to-find-woocommerce-products-without-a-shipping-class/

Just create a new PHP file in wp-content/plugins with the following code:

<?php
 
/**
* Plugin Name: Find Products Without Shipping Class
* Description: Adds a page that lists all products without a shipping class
* Author: Shane Gowland
* License: GPL
* License URI: https://gowland.me
*/
function register_shipping_class_checker_page() {
    add_submenu_page( 'edit.php?post_type=product', 'Missing Shipping Classes', 'No Shipping Class', 'manage_options', 'missing_shipping_classes_page', 'missing_shipping_classes_page_callback' );
}
function missing_shipping_classes_page_callback() {  ?>
 
<div class="wrap">
  <h1>Missing Shipping Classes</h1>
 
<p>The products listed below do not have a Shipping Class assigned.</p>
 
<?php
 
$args = array(
    'post_type' => 'product',
    'posts_per_page' => -1,
    'post_status' => 'publish'
 );
 
    $loop = new WP_Query( $args );
    global $post;
    global $product;
     
    //Count how many products were found so we can give zero-results feedback
    $products_found = 0;
     
    while ( $loop->have_posts() ) : $loop->the_post();
   
         $_product = wc_get_product($post->ID);
        $shipclass = $_product->get_shipping_class();
 
    //Output the product
    if (strlen($shipclass) == 0) {
        echo '<br /> '.get_the_title(). ' — <a target="_blank" href="' . get_edit_post_link($post->ID) . '">Edit Product</a>';
    $products_found++;
    }
 
    endwhile;
    wp_reset_query();
     
    //Output something if the number of results is zero
    if ($products_found == 0) {
        echo "No products were found.";
    }
?>
 
</div>
 
<?php }
add_action('admin_menu', 'register_shipping_class_checker_page',99);