Plugin `afterUpdateSpecificCoupons` isn't working as it should be. Wrong coupons are updated.

[jasperzeinstra]

There's a big bug in de the plugin \Dotdigitalgroup\Email\Plugin\CouponPlugin::afterUpdateSpecificCoupons. It saves the $subject by using the values of the $rule. $subject is the coupon record, $rule is the sales rule record.

    /**
     * @param \Magento\SalesRule\Model\ResourceModel\Coupon $subject
     * @param \Magento\SalesRule\Model\ResourceModel\Coupon $result
     * @param \Magento\SalesRule\Model\Rule $rule
     *
     * @return \Magento\SalesRule\Model\Rule
     */
    public function afterUpdateSpecificCoupons(
        \Magento\SalesRule\Model\ResourceModel\Coupon $subject,
        $result,
        \Magento\SalesRule\Model\Rule $rule = null
    ) {
        if ($rule) {
            //update the generated and the expiration date
            $rule->setData('expiration_date', null);
            $rule->setData('generated_by_dotmailer', '1');
            $subject->save($rule);
        }

        return $rule;
    }

How to reproduce

• Set up a Magento 2.2.6 with sample code
• By default DotMailer isn't enabled, keep it like that
• Check the table salesrule_coupon in the database
• Go to sales rule and open ID 1 ("Buy 3 tee shirts and get the 4th free")
• Set coupon type to Specific coupon and check Use Auto Generation
• Save sales rule and check database table salesrule_coupon
• Notice that the coupon with coupon_id = 1 has changed, but this coupon is connected to rule_id = 4. But we saved rule_id = 1.
• Error is caused in \Dotdigitalgroup\Email\Plugin\CouponPlugin::afterUpdateSpecificCoupons where data of rule object is used to save coupon object.
• Also if DotMailer isn't active I wouldn't expect the variable generated_by_dotmailer to be set to 1.

From my point of view you should check if DotMailer is enabled. There's a helper being defined in the constructer method, but it's not being used in the class. And you should not change the rule, but only the coupon.

If you take a look at how they save date for the coupon in \Magento\SalesRule\Model\ResourceModel\Coupon::updateSpecificCoupons you'll notice that they use the update method. So I think it's also better to use this code in the plugin of DotMailer

            $this->getConnection()->update(
                $this->getTable('salesrule_coupon'),
                $updateArray,
                ['rule_id = ?' => $rule->getId()]
            );

[simon-letch]

Hey @jasperzeinstra,

We're taking a look at this during our current sprint. I'll update again once we've investigated. From a quick initial glance, I can't see why this plugin is required at all.

Simon

[simon-letch]

This has now been released in v3.0.3.