Cancellation or Failure Payment will lead into fatal exception (SW 6.6.x.x)

[rommelfreddy]

If I a cancel the payment or the payment will failure, then a fatal exception will happen within the Shopware Store.

{
  "errors": [
    {
      "code": "0",
      "status": "500",
      "title": "Internal Server Error",
      "detail": "Attempted to load class \u0022AsyncPaymentFinalizeException\u0022 from namespace \u0022Shopware\\Core\\Checkout\\Payment\\Exception\u0022.\nDid you forget a \u0022use\u0022 statement for another namespace?"
    }
  ]
}

Seems like that the Polyfill for PaymentException Class is loaded before Shopware, so the class will be Polyfill-Class will be registered before the Shopware-Class is registered.

Personal opinion of DEV: I do not think it is a good idea, to have too many polyfill for Shopware. It would be better to restrict the compatibility to the Shopware versions. I also develop a few payment provider extensions, and we decided to do not keep the compatibility to lower SW-Versions if the codebase is too different (e.g. missing exception-classes)

Much better solution:

protected function createPaymentException(string $orderTransactionId, string $errorMessage, ?\Throwable $e = null): \Throwable  
{
  if (class_exists(PaymentException::class)) {
      return PaymentException::asyncProcessInterrupted($orderTransactionId, $errorMessage, $e);
  } elseif (class_exists(SyncPaymentProcessException::class)) {
      // required for shopware version <= 6.5.3
      return SyncPaymentProcessException($orderTransactionId, $errorMessage, $e);  // @phpstan-ignore-line
  }

  // should never occur, just to be safe.
  return \RuntimeException('payment process was interrupted ' . $orderTransactionId);
}