How to override system.mail.yml in Drupal 8? - smtp

Question

I have the below code in my file: core\modules\system\config\install\system.mail.yml
interface:
default: 'php_mail'
I want to change the code to:
interface:
default: 'SMTPMailSystem'
In order to get my SMTP module to work. On changing the code in the core file my module works. Since making direct changes in core file is not good I want to know how do we override such files. I am fairly new to Drupal 8 hence couldn't get through.

Answer 1

Drupal has an article on Configuration override system, which gives an overview and starter code to override configurations defined in *.yml . You can jump to "Providing overrides from modules" section right away for your case.
In short:
Create a module (config_example used as an example)
Create a config_example.services.yml, and put:
services:
config_example.overrider:
class: \Drupal\config_example\ConfigExampleOverrides
tags:
- {name: config.factory.override, priority: 5}
config.factory.override is the important thing here, others are up to you to change.
Define the class which implements ConfigFactoryOverrideInterface:
namespace Drupal\config_example;
use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Config\ConfigFactoryOverrideInterface;
use Drupal\Core\Config\StorageInterface;
/**
* Example configuration override.
*/
class ConfigExampleOverrides implements ConfigFactoryOverrideInterface {
/**
* {#inheritdoc}
*/
public function loadOverrides($names) {
$overrides = array();
if (in_array('system.mail', $names)) { // (a)
$overrides['system.mail'] = [
'interface' => ['default' => 'SMTPMailSystem']
];
}
return $overrides;
}
/**
* {#inheritdoc}
*/
public function getCacheSuffix() {
return 'ConfigExampleOverrider'; // (c)
}
/**
* {#inheritdoc}
*/
public function getCacheableMetadata($name) {
return new CacheableMetadata();
}
/**
* {#inheritdoc}
*/
public function createConfigObject($name, $collection = StorageInterface::DEFAULT_COLLECTION) {
return NULL;
}
}
The following thing is changed to work for your case:
(a) The in_array needle is changed to system.mail which is the YML you wish to override. The value assigned to $overrides['system.mail'] is changed to what you wish to be placed.