This commit adds the exception message thrown when WC_Order::set_billing_email() is called with an invalid message to a test to fix it.
I couldn't find what change in WC codebase broke the test and I'm not sure why it is failing only when running using PHP 5.6:
https://travis-ci.org/woocommerce/woocommerce/jobs/315750242#L600
If by default the taxes are based on the shipping address and the current order doesn't have any, it would use the billing address rather than using the Shopping base location.
It's basically what WooCommerce is [doing already in Javascript](https://github.com/woocommerce/woocommerce/blob/master/assets/js/admin/meta-boxes-order.js#L526-L575). This kind of checks should be done in the backend, never in the client side.
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).
Rodrigo Primo
Claudiu Lodromanean
Claudio Sanches
ragulka
Mike Jolley
Trey Richards
Brent Shepherd
Cesar Rodas
Paul Kilmurray