jigoshop_actions.php

//variaton wasn't selected but user managed to submit a form
            if (empty($_POST['variation_id']) || !is_numeric($_POST['variation_id'])) {
                /* Link on product pages */
                jigoshop::add_error(__('Please choose product options…', 'jigoshop'));
                wp_redirect(get_permalink($_GET['product']));
                exit;
            } else {
                $product_id = apply_filters('jigoshop_product_id_add_to_cart_filter', (int) $_POST['product_id']);
                $variation_id = (int) $_POST['variation_id'];
                $customer_design = $_POST['customer_design'];
                $quantity = 1;
                if (isset($_POST['quantity'])) {
                    $quantity = (int) $_POST['quantity'];
                }

                if ( get_post_meta( $product_id , 'customizable', true ) == 'yes' ) {
                    // session personalization initially set to parent product until variation selected
                    $custom_products = (array) jigoshop_session::instance()->customized_products;
                    // transfer it to the variation
                    $custom_products[$variation_id] = $custom_products[$product_id];
                    unset( $custom_products[$product_id] );
                    jigoshop_session::instance()->customized_products = $custom_products;
                }

                $attributes = (array) maybe_unserialize(get_post_meta($product_id, 'product_attributes', true));
                $variations = array();
                $all_variations_set = true;

                foreach ($attributes as $attribute) {

                    if ( ! $attribute['variation']) {
                        continue;
                    }

                    $attr_name = 'tax_' . sanitize_title($attribute['name']);
                    if (!empty($_POST[$attr_name])) {
                        $variations[$attr_name] = $_POST[$attr_name];
                    } else {
                        $all_variations_set = false;
                    }
                }

                if ($all_variations_set && $variation_id > 0) { //all variation options are set
                    jigoshop_cart::add_to_cart($product_id, $quantity, $variation_id, $variations, $customer_design);

                    $product_added = true;
                } else {
                    /* Link on product pages */
                    jigoshop::add_error(__('Please choose product options…', 'jigoshop'));
                    wp_redirect(apply_filters('jigoshop_product_id_add_to_cart_filter', get_permalink($_GET['product'])));
                    exit;
                }
            }