Notes from an email on the google group:
When a customer uses a gift certificate to make a payment for an order, and if the gift certificate has a lower value than the amount to be paid, then the 'balance remaining' path is entered, however the cart loses key details about the order:
1) Add some items to cart with a total greater than the gift certificate's value
2) At /checkout/, select "Gift certificate"
3) At /checkout/giftcertificate, enter 'Gift Certificate Code', select shipping
3) At /checkout/giftcertificate/confirm, details all fine, select "Purchase Items"
4) At /checkout/balance/[order payment number]/
This is the page at which the customer must choose how to pay the remaining balance of the order. At this point the cart reads "Your shopping cart contains 1 item totalling $0.00". Select payment method and hit "Continue".
5) At /checkout/[payment method]/confirm/
At this point, the card reads "Your shopping cart is empty". However it is usually possible to submit the order at this point to make it to the success page.
Once the errors start, I have found that the following items can no longer be accessed through the shop templates, or have erroneous values: 1. order.shipping_method = No Shipping, regardless of the shipping method chosen 2. order.orderstatus_set contains status.status|status_label = Shipped and status.notes = "Order immediately available for download", even though the item is not a downloadable product 3. order.orderitem_set is empty
In the admin page, the Product Order is received, however the order has the following issues: 1. Shipping method = No Shipping, regardless of method chosen 2. Shipping cost = $0 3. Order Line Items is empty (also does not appear in Order Line Items /admin/shop/orderitem/)
However following items in the Product Order are correct: 1. Subtotal 2. Total 3. Order Payments and amounts
I initially created a work-around, deducing the shipping method from the difference between the subtotal and total, and editing _order_tracking_details.html and _order_details.html to handle and cover-up the erroneous details, however unless I can find where the order items are going to I don't think I'll be able to create a work- around to use the gift certificates, as I have no solid way of determining what was ordered from the subtotal alone.