Argument 1 passed to Drupal\commerce_order\PriceCalculator::calculate() must implement interface Drupal\commerce\PurchasableEntityInterface, null given

This error is triggered because the code assumes that $order_item->getPurchasedEntity() will always return an entity, but this can return NULL:

/**
 * Gets the purchased entity.
 *
 * @return \Drupal\commerce\PurchasableEntityInterface|null
 *   The purchased entity, or NULL.
 */
public function getPurchasedEntity();

This can easily happen in practice, when locked carts contains a product variation that have been deleted.

An simplier alternative patch to #1 is provided.

Reviewed the patch code and tested it locally. Looks like its working perfect. Moving to RTBC

Patch from #2 works good for me. Thanks a lot!

Patch #2 is worked against error, but now I have many cart forms on cart page: https://i.imgur.com/GsoBQDM.jpg

chetan 11 → made their first commit to this issue’s fork.

Hi,
I have fixed the above error on "price difference formatter" module.
Please check the raised MR.
Thanks.