Right now get_item() is loading an item from the database directly. It doesn't
take advantage of our cache and it doesn't check if the item is already loaded in memory.
There is also another bug (or feature?) that it will let you load any item, even if the item is not related to the current order. I believe this is a bug, if somebody really wants to load any item regardless of the order they should use `WC_Order_Factory::get_order_item`.
Another bug is that items loaded with get_item() are not related to the order object, therefore any calls to Order::save() won't persist the changes made to the item.
This commits makes sure the item returned by get_item is loaded similarly like get_items() does, taking advantage of the cache and the $items protected property (chances are the item is already in memory, ready to be used).
If a given item is not found false will be returned. If item exists but it is not related to the current object it will return false as well (If this behaviour is wanted, I can easily change it load the item anyways instead of returning false).
Abstract_WC_Order_Data_Store_CPT::read() hardcoded its validation against
the 'shop_order' post type. However, custom order types created via the
wc_register_order_type() API can use different post types. For example,
refunds have the post type: 'shop_order_refund'.
This patch changes the Abstract_WC_Order_Data_Store_CPT::read() validation
to check that the post type is any of the registered order types.
This fixes refunds and 3rd party custom order types, like subscriptions.
Mike Jolley
Cesar Rodas
Rasmus Bengtsson
Justin Shreve
JeroenSormani
Claudio Sanches
Brent Shepherd
Manos Psychogyiopoulos