Send a comma separated list of line items (truncates the end of the line item name to return 25 characters) when there's a promotion code on the transaction. Event Espresso 4, PayPal Pro gateway.

paypal_pro_promotions_line_item_name.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_filter(
  'EEG_Paypal_Pro__do_direct_payment__partial_amount_line_item_name',
  'my_custom_paypal_pro_line_items_with_promotions',
  10,
  3
);

function my_custom_paypal_pro_line_items_with_promotions(
  $string,
  $object,
  $payment
) {
  $transaction = $payment->transaction();
  if (! $transaction instanceof EE_Transaction) {
    return $string;
  }
  $total_line_item = $transaction->total_line_item();
  if (! $total_line_item instanceof EE_Line_Item) {
    return $string;
  }
  $order_items = array();
  foreach ($total_line_item->get_items() as $line_item) {
      // ignore line items with a quantity of 0
      if ($line_item->quantity() == 0) {
          continue;
      }
      $item = substr(
              $line_item->name(),
              0,
              25
      );
      array_push($order_items, $item);
  }
  $string = implode(",", $order_items);
  return $string;
}