Preference is not working in Magento 2

Question

I am trying to override ErrorHandler class using preference but it is not working. di.xml

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
   <preference for="Magento\Framework\App\ErrorHandler" type="Pulsestorm\HelloWorldMVVM\Model\ErrorHandler"/>

</config>    

ErrorHandler.php

<?php
namespace Pulsestorm\HelloWorldMVVM\Model;

class ErrorHandler extends \Magento\Framework\App\ErrorHandler{
    public function getHandler()
    { echo"hii"; exit;
        if (strpos($errorStr, 'DateTimeZone::__construct') !== false) {
            // there's no way to distinguish between caught system exceptions and warnings
            return false;
        }

        $errorNo = $errorNo & error_reporting();
        if ($errorNo == 0) {
            return false;
        }

        $msg = isset($this->errorPhrases[$errorNo]) ? $this->errorPhrases[$errorNo] : "Unknown error ({$errorNo})";
        $msg .= ": {$errorStr} in {$errorFile} on line {$errorLine}";
        throw new \Exception($msg);
    }
}    

I used echo exit to check preference is working or not. When any error or exception comes it doesn't echo and exit. Please let me know what I am doing wrong. Thank you in advance.

Answer 1

class name was wrong, you mentioned Pulsestorm\HelloWorldMVVM\Model\Errors so it should be

<?php
namespace Pulsestorm\HelloWorldMVVM\Model;

class Errors extends \Magento\Framework\App\ErrorHandler{
    .....................
    .....................
    .....................
    .....................
}

Answer 2

Check to see that someone else has already preferenced the targeted class:-

find vendor/ -name "di.xml" -exec egrep "ErrorHandler" {}  \; 

and try to scan your custom code folder:

find app/code -name "di.xml" -exec egrep "ErrorHandler" {}  \; 

Answer 3

I've encountered a similar kind of problem, as the preference was not working.

While debugging I found there were some private properties in the original class file.

Then I added all those private properties as protected into the preferenced/over-rided file and then it worked.

---

Maybe this can be helpful for someone.

Answer 4

your preference in di.xml should be like this :

<?xml version="1.0"?>

  <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
      <preference for="Magento\Framework\App\ErrorHandler" type="Pulsestorm\HelloWorldMVVM\Model\ErrorHandler"/>

</config> 

As you have declared your class name same.

Answer 5

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">
   <preference for="Magento\Framework\App\ErrorHandler" type="Pulsestorm\HelloWorldMVVM\Model\Errors"/>

</config> 

You have to declare classname ErrorHandler instead of Errors

 <?php
namespace Pulsestorm\HelloWorldMVVM\Model;

class Errors extends \Magento\Framework\App\ErrorHandler{
    protected $errorPhrases = [
        E_ERROR => 'Error',
        E_WARNING => 'Warning',
        E_PARSE => 'Parse Error',
        E_NOTICE => 'Notice',
        E_CORE_ERROR => 'Core Error',
        E_CORE_WARNING => 'Core Warning',
        E_COMPILE_ERROR => 'Compile Error',
        E_COMPILE_WARNING => 'Compile Warning',
        E_USER_ERROR => 'User Error',
        E_USER_WARNING => 'User Warning',
        E_USER_NOTICE => 'User Notice',
        E_STRICT => 'Strict Notice',
        E_RECOVERABLE_ERROR => 'Recoverable Error',
        E_DEPRECATED => 'Deprecated Functionality',
        E_USER_DEPRECATED => 'User Deprecated Functionality',
    ];

    public function handler($errorNo, $errorStr, $errorFile, $errorLine)
    {   
        echo"hii"; exit;
        if (strpos($errorStr, 'DateTimeZone::__construct') !== false) {
            // there's no way to distinguish between caught system exceptions and warnings
            return false;
        }

        $errorNo = $errorNo & error_reporting();
        if ($errorNo == 0) {
            return false;
        }

        $msg = isset($this->errorPhrases[$errorNo]) ? $this->errorPhrases[$errorNo] : "Unknown error ({$errorNo})";
        $msg .= ": {$errorStr} in {$errorFile} on line {$errorLine}";
        throw new \Exception($msg);
    }
}