Refer A Friend - Exclude sale items from referral discounts

functions.php

<?php

add_filter('automatewoo/referrals/coupon_data', 'my_automatewoo_referrals_coupon_data' );

/**
 * @param array $coupon_data
 * @return array
 */
function my_automatewoo_referrals_coupon_data( $coupon_data ) {
	$coupon_data['exclude_sale_items'] = true;
	return $coupon_data;
}