split 1 cart item into instock and back ordered

Question

If I have a stock count of 2 and I allow backorders and a client adds a quantity of 5 to the cart, the cart shows 1 line item with a quantity of 5 on backorder.

Is there a way to split this cart entry into 2, one line with the quantity in stock and the second with the backorder amount?

So if I have 2 in stock and the user adds 5 to the cart they will see two line items:

Product name - Qty: 2

Product name (backorder) - Qty: 3

Answer 1

Here is a plugin that does this in case someone else needs it. Just save this in

<?php
/*
Plugin Name: WC Split Cart Backorders 
Plugin URI: https://www.creativemonarchy.com
Description: A simple plugin that helps you split the WooCommerce in stock and backorder stock items for the same product in your cart.
Author: Sohrab Iravani
Version: 1.0
Author URI: https://www.creativemonarchy.com
Requires at least: 4.9
Tested up to: 5.2.3
Text Domain: wc_split_cart_backorder
Domain Path: /languages/
*/

// Split in stock orders and backorders in the cart
add_action( 'woocommerce_add_to_cart', 'split_bkorders', 10, 6 );
function split_bkorders( $cart_item_key, $product_id, $quantity, $variation_id, $variation, $cart_item_data ) {
    foreach ( WC()->cart->get_cart() as $cart_item ) {
        $quantity;
        $product = $cart_item['data'];
        $stock_qty = $product->get_stock_quantity();
        $item_qty  = $cart_item['quantity'];
        if ($quantity > $stock_qty && $stock_qty > 0) {
            WC()->cart->set_quantity( $cart_item_key, $stock_qty );
            $backorder = $item_qty - $stock_qty;
            $cart_item_data['unique_key'] = md5( microtime() . rand() . "xxx" );
            $cart_item_data['pr_field'] = 'backorder';
            WC()->cart->add_to_cart( $product_id, 1, $variation_id, $variation, $cart_item_data );
            $count = 0;
            foreach (WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
                if ($count == 1) {
                    WC()->cart->set_quantity( $cart_item_key, $backorder );
                    break;
                }
                $count++;
            }
        } elseif ($stock_qty < 0) {
            $cart_item_data = 'backorder';
            WC()->cart->cart_contents[$cart_item_key]['pr_field'] = $cart_item_data;
        }
        break;
    }
}
// Add custom field "backorder" to cart item
function plugin_republic_get_item_data( $item_data, $cart_item_data ) {
    if( isset( $cart_item_data['pr_field'] ) ) {
        $item_data[] = array(
            'key' => __( 'Type', 'plugin-republic' ),
            'value' => wc_clean( $cart_item_data['pr_field'] )
        );
    }
    return $item_data;
}
// Add custom field "backorder" to everywhere
add_filter( 'woocommerce_get_item_data', 'plugin_republic_get_item_data', 10, 2 );
function plugin_republic_checkout_create_order_line_item( $item, $cart_item_key, $values, $order ) {
    if( isset( $values['pr_field'] ) ) {
        $item->add_meta_data(
            __( 'Type', 'plugin-republic' ),
            $values['pr_field'],
            true
        );
    }
}
add_action( 'woocommerce_checkout_create_order_line_item', 'plugin_republic_checkout_create_order_line_item', 10, 4 );
// Disable default backorder notification in cart
function inline_css() {
    echo "<style>.backorder_notification{display: none;}</style>";
}
add_action( 'wp_head', 'inline_css', 0 );
// Disable quanity edit in cart
add_filter( 'woocommerce_cart_item_quantity', 'wc_cart_item_quantity', 10, 3 );
function wc_cart_item_quantity( $product_quantity, $cart_item_key, $cart_item ){
    if( is_cart() ){
        $product_quantity = sprintf( '%2$s <input type="hidden" name="cart[%1$s][qty]" value="%2$s" />', $cart_item_key, $cart_item['quantity'] );
    }
    return $product_quantity;
}
// Create new order status "Partial Order"
add_filter( 'woocommerce_register_shop_order_post_statuses', 'bbloomer_register_custom_order_status' );
function bbloomer_register_custom_order_status( $order_statuses ){
    $order_statuses['wc-partial-order'] = array(
        'label'                     => _x( 'Partial Order', 'Order status', 'woocommerce' ),
        'public'                    => false,
        'exclude_from_search'       => false,
        'show_in_admin_all_list'    => true,
        'show_in_admin_status_list' => true,
        'label_count'               => _n_noop( 'Partial Order <span class="count">(%s)</span>', 'Partial Order <span class="count">(%s)</span>', 'woocommerce' ),
    );
    return $order_statuses;
}
add_filter( 'wc_order_statuses', 'bbloomer_show_custom_order_status' );
function bbloomer_show_custom_order_status( $order_statuses ) {
    $order_statuses['wc-partial-order'] = _x( 'Partial Order', 'Order status', 'woocommerce' );
    return $order_statuses;
}
add_filter( 'bulk_actions-edit-shop_order', 'bbloomer_get_custom_order_status_bulk' );
function bbloomer_get_custom_order_status_bulk( $bulk_actions ) {
    $bulk_actions['mark_partial-order'] = 'Change status to partial order';
    return $bulk_actions;
}
// Update mix order to Partial Order
add_filter( 'woocommerce_thankyou_order_received_text', 'misha_thank_you_title', 20, 2 );
function misha_thank_you_title( $thank_you_title, $order ){
    $items = $order->get_items();
    $backorders = 0;
    $order_count = 0;
    foreach ( $items as $item_id => $item ) {
        if (wc_get_order_item_meta( $item_id, 'Type', true) == 'backorder') {
            $backorders++;
        }
        $order_count++;
    }
    if ($backorders > 0) {
        if ($order_count == $backorders) {
            $order->update_status('backordered', 'order_note');
        } else {
            $order->update_status('partial-order', 'order_note');
        }
    }
}
?>