Add Supplier Code field input @ product edit page

<?php
/*
Plugin Name: Add Supplier Code field
Plugin URI: https://www.facebook.com/groups/advanced.woocommerce/permalink/1968581709822905/
Description: Request on Facebook Advanced WooCommerce group - add Supplier Code field.
Author: Damien Carbery
Author URI: http://www.damiencarbery.com
Version: 0.1
*/

// 1. Add Supplier Code field input @ product edit page

add_action( 'woocommerce_product_options_sku', 'bbloomer_add_supplier_code_to_products' );

function bbloomer_add_supplier_code_to_products() {
    woocommerce_wp_text_input( array(
                        'id' => '_supplier_code',
                        'class' => 'short wc_input_price',
                        'label' => __( 'Supplier Code', 'woocommerce' )
                        )
                        );
}

// -----------------------------------------
// 2. Save Supplier Code field via custom field

add_action( 'save_post', 'bbloomer_save_supplier_code' );

function bbloomer_save_supplier_code( $product_id ) {
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
        return;

    if ( isset( $_POST['supplier_code'] ) ) {
        if ( is_numeric( $_POST['_supplier_code'] ) )
            update_post_meta( $product_id, '_supplier_code', $_POST['supplier_code'] );
    } else delete_post_meta( $product_id, '_supplier_code' );
}