How to validate a custom field in sales rule before the discount applying to cart in magento 2.4

Question

I created three custom fields in salesrule Database Table.

1. apply_on_weekday
2. applicable_time_from
3. applicable_time_to

Now I wants to validate that custom fields before the applying the cart price rule to cart. but i haven't any idea about it.

for example :- first check date. if date is valid then need to check weekday, & then if weekday also valid then check time from & to values.

if all custom field validate is true then after, apply sales rule as normal flow as magento core.

here apply_on_weekday field has value as Fri,Sat,Sun. convert string to array then validate day is valid or not using current day of datetime of store.

Answer 1

To add validation for custom salesrule, you should add an after plugin to Magento\SalesRule\Model\Utility::canProcessRule method.

I'll tell you how to validate the apply_on_weekday custom field, then you can extend the plugin class to add validation for applicable_time_from and applicable_time_to.

Assume you named the vendor name Vendor, and the module name Module (You can change the vendor name and module name). Take the following steps:

Step 1: Create the registration.php file:
File path: app/code/Vendor/Module/registration.php

<?php
use Magento\Framework\Component\ComponentRegistrar;
ComponentRegistrar::register(ComponentRegistrar::MODULE, 'Vendor_Module', DIR);

Step 2: Create the module.xml file:
File path: app/code/Vendor/Module/etc/module.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="Vendor_Module">
        <sequence>
            <module name="Magento_SalesRule"/>
        </sequence>
    </module>
</config>

Step 3: Create di.xml file:
File path: app/code/Vendor/Module/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\SalesRule\Model\Utility">
        <plugin name="ValidateWeekdayCondition" type="Vendor\Module\Plugin\ValidateWeekdayCondition"/>
    </type>
</config>

Step 4: Create ValidateWeekdayCondition.php file.
File path: app/code/Vendor/Module/Plugin/ValidateWeekdayCondition.php

<?php
declare(strict_types=1);
namespace Vendor\Module\Plugin;
use Magento\SalesRule\Model\Utility;
use Magento\Framework\Stdlib\DateTime\TimezoneInterface;
class ValidateWeekdayCondition
{
    /**
     * @var TimezoneInterface
     */
    protected $timezoneInterface;
/**
 * @param TimezoneInterface $timezoneInterface
 */
public function __construct(
    TimezoneInterface $timezoneInterface
) {
    $this-&gt;timezoneInterface = $timezoneInterface;
}

/**
 * after the canProcessRule, Check if salesRule can be applied for the day of the week
 *
 * @param  \Magento\SalesRule\Model\Utility $subject
 * @param  boolean $result
 * @param  \Magento\SalesRule\Model\Rule $rule
 * @param  \Magento\Quote\Model\Quote\Address $address
 * @return boolean
 */
public function afterCanProcessRule(Utility $subject, bool $result, $rule, $address)
{
    if ($result) {
        if ($applyOnWeekday = $rule-&gt;getApplyOnWeekday()) {
            // $currentWeekday = (new \DateTime())-&gt;format('D');
            $currentWeekday = $this-&gt;timezoneInterface-&gt;date()-&gt;format('D'); // get current store Weekday
            $applyOnWeekday = explode(',', $applyOnWeekday);
            if (!in_array($currentWeekday, $applyOnWeekday)) {
                $result = false;
            }

            // Add new code here to validate applicable_time_from and applicable_time_to
        } else {
            // No weekdays applied
            $result = false;
        }
    }

    return $result;
}

}

Step 5: Finally, run the setup:upgrade command to make your new module active, and then compile code, deploy static content:

bin/magento setup:upgrade
bin/magento setup:di:compile
bin/magento setup:static-content:deploy -f

Done.