Resolve Can not export Coupon Code to CSV issue29277

Author: edenduong

app/code/Magento/SalesRule/Controller/Adminhtml/Promo/Quote/ExportCouponsCsv.php

@@ -15,13 +15,14 @@
 use Magento\Framework\View\Result\Layout;
 use Magento\Framework\App\ResponseInterface;
 use Magento\Framework\App\Action\HttpGetActionInterface;
+use Magento\Framework\App\Action\HttpPostActionInterface;
 
 /**
  * Export Coupons to csv file
  *
  * Class \Magento\SalesRule\Controller\Adminhtml\Promo\Quote\ExportCouponsCsv
  */
-class ExportCouponsCsv extends Quote implements HttpGetActionInterface
+class ExportCouponsCsv extends Quote implements HttpGetActionInterface, HttpPostActionInterface
 {
     /**
      * Export coupon codes as CSV file