WooCommerce Products Sort and Display by a Custom meta field

gistfile1.txt

/**
 * Add Publish Year sorting option to shop page / WC Product Settings - WooCommerce
 */
function thbc_publishyear_woocommerce_shop_ordering( $sort_args ) {
  $orderby_value = isset( $_GET['orderby'] ) ? woocommerce_clean( $_GET['orderby'] ) : apply_filters( 'woocommerce_default_catalog_orderby', get_option( 'woocommerce_default_catalog_orderby' ) );
 
    if ( 'publishyear' == $orderby_value ) {
        $sort_args['orderby'] = 'title';
        $sort_args['order'] = 'asc'; //or desc
        $sort_args['meta_key'] = 'publish-year';
    }
    return $sort_args;
}
add_filter( 'woocommerce_get_catalog_ordering_args', 'thbc_publishyear_woocommerce_shop_ordering' );
function thbc_publishyear_woocommerce_catalog_orderby( $sortby ) {
    $sortby['publish-year'] = 'Sort by publish year';
    return $sortby;
}
add_filter( 'woocommerce_default_catalog_orderby_options', 'thbc_publishyear_woocommerce_catalog_orderby' );
add_filter( 'woocommerce_catalog_orderby', 'thbc_publishyear_woocommerce_catalog_orderby' );