magento Plugin is not working on CollectRates method shipping method class

Question

Target:

Using plugin before method, want to changes some behavior of method collectRates(RateRequest $request) of Magento\OfflineShipping\Model\Carrier\Freeshipping

Issue:

Getting 500 Internal Server Error for parameters of beforeCollectRates().

Error message: Warning: array_values() expects parameter 1 to be array, object

{"message":"Warning: array_values() expects parameter 1 to be array, object given in /var/www/html/extension/vendor/magento/framework/Interception/Interceptor.php on line 146","trace":"#0 [internal function]: Magento\Framework\App\ErrorHandler->handler(2, 'array_values() ...', '/var/www/html/e...', 146, Array)\n#1 /var/www/html/extension/vendor/magento/framework/Interception/Interceptor.php(146): array_values(Object(Magento\Quote\Model\Quote\Address\RateRequest))\n#2 /var/www/html/extension/var/generation/Magento/OfflineShipping/Model/Carrier/Freeshipping/Interceptor.php(26): Magento\OfflineShipping\Model\Carrier\Freeshipping\Interceptor->___callPlugins('collectRates', Array, Array)\n#3 /var/www/html/extension/vendor/magento/module-shipping/Model/Shipping.php(293): Magento\OfflineShipping\Model\Carrier\Freeshipping\Interceptor->collectRates(Object(Magento\Quote\Model\Quote\Address\RateRequest))\n#4 /var/www/html/extension/vendor/magento/module-shipping/Model/Shipping.php(209): Magento\Shipping\Model\Shipping->collectCarrierRates('freeshipping', Object(Magento\Quote\Model\Quote\Address\RateRequest))\n#5 /var/www/html/extension/vendor/magento/module-quote/Model/Quote/Address.php(995): Magento\Shipping\Model\Shipping->collectRates(Object(Magento\Quote\Model\Quote\Address\RateRequest))\n#6 /var/www/html/extension/vendor/magento/module-quote/Model/Quote/Address.php(936): Magento\Quote\Model\Quote\Address->requestShippingRates()\n#7 /var/www/html/extension/vendor/magento/module-quote/Model/Quote/Address/Total/Shipping.php(161): Magento\Quote\Model\Quote\Address->collectShippingRates()\n#8 /var/www/html/extension/vendor/magento/module-quote/Model/Quote/TotalsCollector.php(265): Magento\Quote\Model\Quote\Address\Total\Shipping->collect(Object(Magento\Quote\Model\Quote), Object(Magento\Quote\Model\ShippingAssignment), Object(Magento\Quote\Model\Quote\Address\Total))\n#9 /var/www/html/extension/vendor/magento/module-quote/Model/ShippingMethodManagement.php(273): Magento\Quote\Model\Quote\TotalsCollector->collectAddressTotals(Object(Magento\Quote\Model\Quote), Object(Magento\Quote\Model\Quote\Address))\n#10 /var/www/html/extension/vendor/magento/module-quote/Model/ShippingMethodManagement.php(213): Magento\Quote\Model\ShippingMethodManagement->getShippingMethods(Object(Magento\Quote\Model\Quote), Array)\n#11 [internal function]: Magento\Quote\Model\ShippingMethodManagement->estimateByExtendedAddress('8', Object(Magento\Quote\Model\Quote\Address))\n#12 /var/www/html/extension/vendor/magento/module-webapi/Controller/Rest.php(307): call_user_func_array(Array, Array)\n#13 /var/www/html/extension/vendor/magento/module-webapi/Controller/Rest.php(216): Magento\Webapi\Controller\Rest->processApiRequest()\n#14 /var/www/html/extension/var/generation/Magento/Webapi/Controller/Rest/Interceptor.php(37): Magento\Webapi\Controller\Rest->dispatch(Object(Magento\Framework\App\Request\Http))\n#15 /var/www/html/extension/vendor/magento/framework/App/Http.php(135): Magento\Webapi\Controller\Rest\Interceptor->dispatch(Object(Magento\Framework\App\Request\Http))\n#16 /var/www/html/extension/vendor/magento/framework/App/Bootstrap.php(258): Magento\Framework\App\Http->launch()\n#17 /var/www/html/extension/index.php(39): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http))\n#18 {main}"}

Code:

<?php
namespace Devamitbera\CoreRewrite\Plugin;

class FreeShippingPlugin
{
    public function beforeCollectRates(
        \Magento\OfflineShipping\Model\Carrier\Freeshipping $subject ,
            \Magento\Quote\Model\Quote\Address\RateRequest $request)
    {

        return $request;

    }

}

Question:

Why i getting issue at parameters of beforeCollectRates()?

Answer 1

try

return [$request];

The Interceptor is looking for an array as return value from the before method:

            $beforeResult = $pluginInstance->$pluginMethod($this, ...array_values($arguments));
            if ($beforeResult) {
                $arguments = $beforeResult;
            }

            [..snip..]

            $result = parent::$method(...array_values($arguments));

see here.

Answer 2

Adding to @Kristof at Fooman answer,

When you set to return false to in your before plugin , Magento itself call the original method thats why your return false seems not working. In that case you can use after plugin to change the return value. As per I know before plugin change only the arguments of the method not the return value.