Bug with negative amounts in PayPal API - paypal

Question

I'm trying to use a negative amount with the PayPal Adaptive Payments API. To start with, this seems to work:
'item' => [
{
'itemPrice' => '25.00',
'name' => 'Cryptex - 16Gb USB Drive',
'price' => '25',
'itemCount' => 1
},
{
'quantity' => 1,
'name' => 'Special Discount',
'price' => '-2.50'
},
{
'itemPrice' => '5.00',
'name' => 'Shipping',
'price' => '5.00',
'itemCount' => 1
}
]
Here is an example of what I see after submitting this as JSON, and updating the items:
As you can see, the price IS correct ... yet there is no sign of the discounted amount? Its obviously taking it into account - otherwise the price would have been £30, not £27.50 (which is after the £2.50 discount)
What gives? Is this a bug in PayPals system?
FWIW, the emails are also broken - they don't show the discount amount at all.
UPDATE: I've opened a ticket with PayPal tech support, as I'm pretty sure this is a bug with their system, and not something that can be fixed this end :( Damn annoying!
UPDATE 2: Reply from PayPal:
PayPal Adaptive Payments do not support negative item values. Since you did not pass the <itemPrice> in your API Call, the system did not throw the following error message:
[errorId] => 580022
[domain] => PLATFORM
[subdomain] => Application
[severity] => Error
[category] => Application
[message] => Invalid request parameter: itemPrice cannot be negative
I can see that the following was submitted to PayPal:
<item>
<name>Special Discount</name>
<identifier></identifier>
<price>-2.50</price>
<itemPrice></itemPrice>
<itemCount></itemCount>
<any>[quantity: null]</any>
</item>
This object is basically incomplete and in order to apply discounts, you should apply them > onto the price for the main item and then submit it to PayPal.
I'm really not sure what they're suggestion I do? An example cart, would be:
Item 1 - £10
Item 2 - £20
Item 3 - £50
Item 4 - £10
Delivery - £5
Total - £95
As an encouragement, we sometimes will offer coupons... so it could be "£10 off orders over £50". So in the above case above, it would drop the overall price to £85.
I'm really not sure what they are suggesting as an alternative?

Answer 1

Interesting. Normal payments don't have that restriction (I pass a negative amount item just like what you describe on a frequent basis).
What they're telling you to do is take the discount off another item. So your example cart with that discount would be
Item 1 - £10
Item 2 - £20
Item 3 - £40 <-- Removed £10 discount
Item 4 - £10
Delivery - £5
Total - £85 <-- total reflects this