Re: Free Shipping Bug

I'm trying to track down a bug in getpaid that seems to allow a user to get free shipping.  I've been able to get to a point were I can reproduce it, now I'm looking for pointers or help on why it is occuring.

I've got a simple setup of Plone 3.1.6 with GetPaid 0.7.9 (I'm using the svn checkout of the buildout).  I've marked a couple of items as shippable and have written my own shipping addon that talks to USPS.

The free shipping issues happens when a user walks through the checkout process up to the 'checkout-review-pay' step.  At this point if the user hits the 'Back' button provided on the page (not the browser back), they return to the 'checkout-select-shipping' step with a hidden element that holds their previous shipping choice.  This input element is the same as the input radio select on the page.  This shouldn't be a problem since I would expect to get both the hidden value and the radio select in an array, and it looks like the code expects that as well since the getShippingMethodCode() does this:

    if isinstance( service_code, list):
        service_code = service_code[-1]

  however it seems I'm getting an empty array instead of an array with two values.  For some clarity the checkout-shipping-select html essentially looks like this:

    <form action="https://nwei.org/@@getpaid-checkout-wizard"
          method="post" enctype="multipart/form-data">
         <input type="hidden" name="shipping_method_code" value="usps.D-16"></div> 

         <I removed all the other hidden inputs>

         <input checked type="radio"
                     name="shipping_method_code"
                     value="usps.D-16" /> 
               
          <input type="submit" class="button context"
                     id="form.actions.continue"
                     name="form.actions.continue" value="Continue" />
    </form>

As far as I can tell the code should work.  I'm not clear on why self.request.get('shipping_method_code') is [] on the second submit instead of ['usps.D-16', 'usps.D-16']?  Also if I submit the form, then hit 'back' again it works ok since there is no hidden element for an empty array added.

Anyway if anyone has some suggestions on where to look I would really appreciate it.  Thanks.

-Rob