#38671 - Fix sales rules when rule is applied only on shipping amount

Author: Nuranto

app/code/Magento/SalesRule/Model/Validator.php

@@ -532,6 +532,7 @@ public function processShippingAmount(Address $address)
             $address->setBaseShippingDiscountAmount($this->priceCurrency->roundPrice($baseDiscountAmount));
             $appliedRuleIds[$rule->getRuleId()] = $rule->getRuleId();
 
+            $this->rulesApplier->maintainAddressCouponCode($address, $rule, $this->getCouponCode());
             $this->rulesApplier->addDiscountDescription(
                 $address,
                 $rule,