Coupon not marked as used when used to apply free shipping

[danslo]

Steps to reproduce

1. Install Magento from develop branch.
2. Go to Marketing > Cart Price Rules
3. Create a new rule with a Coupon
4. Set Uses per Coupon to '1'.
5. Enable 'Use Auto Generation'.
6. Under 'Actions', enable free shipping.
7. Go through normal checkout process and submit an order.

Expected result

1. The coupon code is marked as used.
2. The number of times used is increased.

## Actual result 1. Used is "No" 2. Times used is "0".

This bug also exists in Magento 1.9.2.4.

[danslo]

The reason for this is the following part of SalesRule observer:

diff --git app/code/Magento/SalesRule/Observer/SalesOrderAfterPlaceObserver.php app/code/Magento/SalesRule/Observer/SalesOrderAfterPlaceObserver.php
index e352ede..c102cd0 100644
--- app/code/Magento/SalesRule/Observer/SalesOrderAfterPlaceObserver.php
+++ app/code/Magento/SalesRule/Observer/SalesOrderAfterPlaceObserver.php
@@ -57,7 +57,7 @@ class SalesOrderAfterPlaceObserver implements ObserverInterface
     {
         $order = $observer->getEvent()->getOrder();

-        if (!$order || $order->getDiscountAmount() == 0) {
+        if (!$order) {
             return $this;
         }

In my view, an applied coupon code is used, regardless of whether or not a discount was placed on the main order, since it can apply to other things (like free shipping). Is there a specific reason for checking discount amount?

[tkacheva]

@danslo thanks for reporting the issue.

MAGETWO-55396

[pboisvert]

thanks @danslo for spotting the duplicates closing as a duplicate of #3506