Compatibilidade do plugin Frenet com classes de entrega do Woocommerce

frenet-shipping-class.php

<?php
/**
* COLOCAR NO FUNCTIONS.PHP DO TEMA
* OU EM ALGUM PLUGIN
*/ 

/**
* Add shipping class field to method settings
* @param array $args Current method settings.
* @return array
*/
function add_shipping_class_fields( $args ){
	$new_field = array(
		'shipping_class' => array(
			'title'       	=> __( 'Shipping Class', 'woocommerce' ),
			'type'        	=> 'multiselect',
			'description' 	=> __( 'If you want, select the authorized shipping class(es) for this method.', 'woocommerce' ),
			'desc_tip'    	=> true,
			'default'     	=> '',
			'class'       	=> 'wc-enhanced-select',
			'options'     	=> get_shipping_classes_options(),
		)
	);

	$args = array_insert_after( $args, 'zip_origin', $new_field );
	return $args;
}
add_filter( 'woocommerce_settings_api_form_fields_frenet', 'add_shipping_class_fields' );
add_filter( 'woocommerce_shipping_instance_form_fields_frenet', 'add_shipping_class_fields' );

/**
* Check if product in cart has selected shipping class
* @param bool $is_available True by default.
* @param array $package Package in WC Cart
* @param WC_Shipping_Method $method Frenet class.
* @return bool
*/
function has_selected_shipping_class( $is_available, $package, $method ) {
	$instance_id = $method->instance_id;

	$option_key = 'woocommerce_frenet_' . $instance_id . '_settings';

	$instance_settings = get_option( $option_key );

	if( ! isset ( $instance_settings['shipping_class'] ) ){
		return $is_available;
	}

	$shipping_classes = $instance_settings['shipping_class'];

	if( ! $shipping_classes || count( $shipping_classes ) <= 0 ) {
		return $is_available;
	}

	$is_available = false;

	foreach( $package['contents'] as $item_id => $values ) {

		$product = $values['data'];
		$qty     = $values['quantity'];

		if( $qty > 0 && $product->needs_shipping() ) {

			if( in_array( (int) $product->get_shipping_class_id(), $shipping_classes ) ) {
				$is_available = true;
				break;
			}
		}
	}

	return $is_available;
}
add_filter( 'woocommerce_shipping_frenet_is_available', 'has_selected_shipping_class', 20, 3 );

/**
* Get all shipping classes
*
*/
function get_shipping_classes_options() {
	$shipping_classes = WC()->shipping->get_shipping_classes();
	$options          = array();

	if ( ! empty( $shipping_classes ) ) {
		$options += wp_list_pluck( $shipping_classes, 'name', 'term_id' );
	}

	return $options;
}

/**
* Helper to insert element after certain index in array
*
*/
function array_insert_after(array $array, $key, array $new)
{
	$keys = array_keys($array);
	$index = array_search($key, $keys);
	$pos = false === $index ? count($array) : $index + 1;

	return array_merge(array_slice($array, 0, $pos), $new, array_slice($array, $pos));
}

Obrigada Victor!