coupon percentage off, free shipping and taxes

[balihr]

I've just noticed something weird in the discounts calculation and am hoping that someone might tell me if I'm missing something or if it's a bug...

Using 1.5.4 clean install. For simpler calculation, I've changed Florida tax rate to 10%.
Created new coupon: 20% off and free shipping.
Added item in cart (Taxable Goods). Using Flat Rate $5.00 (Taxable Goods). Going to checkout using a Florida address.

Here are my totals before applying the coupon:
Sub-Total: 110.97
Flat Rate (Best Way): $5.00
FL TAX 10.0%: $11.60
Total: $127.57

All good.
Now I apply the coupon and this is what I get:
Sub-Total: 110.97
Flat Rate (Best Way): $5.00
Discount Coupon: test :-$27.19
FL TAX 10.0%: $9.38
Total: $98.16

I think this is wrong, isn't it? It seems to be adding shipping tax even though shipping is free.
110.97 + 5 - (22.19 + 5) = 88.78
10% tax on 88.78 should be 8.88. It seems that it's still adding the 0.50 tax from shipping.

Here's what I've done to fix it:
includes/modules/order_total/ot_coupon.php line 419-429

case 'E': // percentage & Free Shipping
              $od_amount['total'] = zen_round($orderTotalDetails['orderTotal']*($coupon->fields['coupon_amount']/100), $currencyDecimalPlaces);
              $od_amount['type'] = $coupon->fields['coupon_type'];
              $ratio = $od_amount['total']/$orderTotalDetails['orderTotal'];
              // add in Free Shipping
              $od_amount['total'] = $od_amount['total'] + $orderTotalDetails['shipping'];
              $od_amount['tax'] = $orderTotalDetails['shippingTax'];
              if (isset($_SESSION['shipping_tax_description']) && $_SESSION['shipping_tax_description'] != '') {
                $od_amount['tax_groups'][$_SESSION['shipping_tax_description']] = $od_amount['tax'];
              }
              break;

replace with:

case 'E': // percentage & Free Shipping
              $od_amount['total'] = zen_round($orderTotalDetails['orderTotal']*($coupon->fields['coupon_amount']/100), $currencyDecimalPlaces);
              $od_amount['type'] = $coupon->fields['coupon_type'];
              // add in Free Shipping
              $od_amount['total'] = $od_amount['total'] + $orderTotalDetails['shipping'];
			  $ratio = $od_amount['total']/$orderTotalDetails['orderTotal'];
              $od_amount['tax'] = $orderTotalDetails['shippingTax'];
              if (isset($_SESSION['shipping_tax_description']) && $_SESSION['shipping_tax_description'] != '') {
                $od_amount['tax_groups'][$_SESSION['shipping_tax_description']] = $od_amount['tax'];
              }
              break;

Basically, I just moved the $ratio line. Of course, same "patch" needs to be done for case O.

Now, since this code was written by Ajeh a long time ago (DiscountCombo_v15B.zip), I'm just not sure if I'm missing something obvious and if it's really supposed to calculate that way OR was it just an oversight and a bug?

[Ajeh]

Using unmodified code I get:

Sub-Total: $110.97
Flat Rate (Best Way): $5.00
Discount Coupon: 20FREESHIP : -$27.19
FL TAX 10.0%: $8.88
Total: $97.66

What happens if you use the original code without any modifications?

[balihr]

Using unmodified code I get:

Really? But I WAS using a clean 1.5.4 install. Absolutely no modifications other than tax rate... Demo products.

Let me do another fresh install and try again.

[balihr]

Oh, I obviously forgot to mention it in my first post - shipping is ALSO set to Taxable Goods.

It's OK if shipping isn't taxable, but if you change Flat Rate to Taxable Goods, you'll see what I'm talking about.

[Ajeh]

On the Modules ... Order Total ... for the Discount Coupon ot_coupon what are your settings?

[balihr]

Standard clean install - I took the 1.5.4 package and did a new install. The ONLY thing I changed was tax rate from 7% to 10%.

To answer your question:
Discount Coupon

This module is installed
true

Sort Order
280

Include Shipping
false

Include Tax
false

Re-calculate Tax
Standard

Tax Class
--none--