Overriding AddToCartForm::submitForm() results in duplicate products added to cart

Problem/Motivation

Currently the AddToCartForm::submitForm() calls parent::submitForm() which implies any class overriding the function should also call parent::submitForm(). When overriding with that assumption you end up in a situation where the commerce_cart submitForm() adds the product to the cart and then your new submitForm() adds the product to the cart resulting in duplicate product submission.

Current work around

My current workaround is to call the grandparent submitForm() directly in the new class which is a bit of php magic.

class CustomAddToCartForm extends AddToCartForm {

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    ContentEntityForm::submitForm($form, $form_state);

    // Additional custom logic here.

    $this->cartManager->addOrderItem($cart, $order_item, $form_state->get([
      'settings',
      'combine',
    ]));
  }

}

Proposed resolution