Configuration Merger 

This class provides a way to merge configurations with equal names from any configuration group and extend one configuration from another. You can also replace some nodes of the original configuration with those that will be extended from this config. For this, set node replace with a list of nodes that you want to replace on the same level as these nodes.

Initialization 

To create a new instance of a merger, you need a list of keys to be used as a sorting order for merging all configurations from groups with an equal name.

namespace Oro\Bundle\ActionBundle\DependencyInjection\CompilerPass;

use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;

class ConfigurationPass implements CompilerPassInterface
{
    /** {@inheritDoc} */
    public function process(ContainerBuilder $container)
    {
       ...
       $bundles = $this->container->getParameter('kernel.bundles');

       $merger = new ConfigurationMerger($bundles);
       ...
    }
}

Usage 

Suppose you need to load configurations from the Resources\config\acme.yml file in any bundle in your application and merge them into final configurations. Here, the bundle to be loaded last overrides some part of the configuration from another bundle. All processes required to load this configuration are below:

namespace Oro\Bundle\ActionBundle\DependencyInjection\CompilerPass;

use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;

class ConfigurationPass implements CompilerPassInterface
{
    /** {@inheritDoc} */
    public function process(ContainerBuilder $container)
    {
       ...
       $bundles = $this->container->getParameter('kernel.bundles');

       $merger = new ConfigurationMerger($bundles);
       ...
    }
}

Examples 

  1. Merge configurations with the same name from two bundles (use append strategy).

Order of loading bundles: FirstBundle, SecondBundle.

# Acme\Bundle\FirstBundle\Resources\config\acme.yml

acme_config:
    param: value
     array_param:
        sub_array_param1: value1
        sub_array_param2: value2

# Acme\Bundle\SecondBundle\Resources\config\acme.yml

acme_config:
    param: replaced_value
     array_param:
          sub_array_param3: value3

Result:

acme_config:
     param: replaced_value
     array_param:
         sub_array_param1: value1
         sub_array_param2: value2
         sub_array_param3: value3

  1. Extend one configuration from another configuration (use append strategy):

# Acme\Bundle\DemoBundle\Resources\config\acme.yml

acme_config_base:
    param: value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    extends: acme_config_base
    new_param: new_value
    array_param:
         sub_array_param3: value3

Result:

acme_config_base:
    param: value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    param: value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2
        sub_array_param3: value3
    new_param: new_value

  1. Merge configurations with the same name from two bundles and extend one configuration from another configuration (use append strategy).

Order of loading bundles: FirstBundle, SecondBundle.

AcmeBundleFirstBundleResourcesconfigacme.yml 
  acme_config_base:
      param: value
      array_param:
          sub_array_param1: value1
          sub_array_param2: value2

  acme_config:
      extends: acme_config_base
      new_param: new_value
      array_param:
          sub_array_param4: value4
AcmeBundleSecondBundleResourcesconfigacme.yml 
  acme_config_base:
      param: replaced_value
      array_param:
          sub_array_param3: value3

Result:

acme_config_base:
    param: replaced_value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2
        sub_array_param3: value3

acme_config:
    param: replaced_value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2
        sub_array_param3: value3
        sub_array_param4: value4
    new_param: new_value

  1. Extends one configuration from another configuration (use append and replace strategies):

AcmeBundleDemoBundleResourcesconfigacme.yml 
  acme_config_base:
      param: value
      array_param:
          sub_array_param1: value1
          sub_array_param2: value2

  acme_config:
      extends: acme_config_base
      replace: [array_param]
      new_param: new_value
      array_param:
          sub_array_param3: value3

Result:

acme_config_base:
    param: value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    param: value
    array_param:
        sub_array_param3: value3
    new_param: new_value

  1. Merge configurations with the same name from two bundles and extend one configuration from another configuration (use append and replace strategy).

Order of loading bundles: FirstBundle, SecondBundle.

# Acme\Bundle\FirstBundle\Resources\config\acme.yml

acme_config_base:
    param: value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    extends: acme_config_base
    new_param: new_value
    array_param:
        sub_array_param4: value4

# Acme\Bundle\SecondBundle\Resources\config\acme.yml

acme_config_base:
    param: replaced_value
    array_param:
        sub_array_param3: value3

Result:

acme_config_base:
     param: replaced_value
     array_param:
         sub_array_param1: value1
         sub_array_param2: value2
         sub_array_param3: value3

acme_config:
    param: replaced_value
    array_param:
         sub_array_param1: value1
         sub_array_param2: value2
         sub_array_param3: value3
         sub_array_param4: value4
     new_param: new_value

  1. Extends one configuration from another configuration (use append and replace strategies).

# Acme\Bundle\DemoBundle\Resources\config\acme.yml

acme_config_base:
     param: value
     array_param:
        sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    extends: acme_config_base
    replace: [array_param]
    new_param: new_value
    array_param:
        sub_array_param3: value3

Result:

acme_config_base:
    param: value
    array_param:
     sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    param: value
    array_param:
        sub_array_param3: value3
    new_param: new_value

  1. Merge configurations with the same name from two bundles and extend one configuration from another configuration (use append and replace strategy).

Order of loading bundles: FirstBundle, SecondBundle.

# Acme\Bundle\FirstBundle\Resources\config\acme.yml

acme_config_base:
    param: value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2

acme_config:
    extends: acme_config_base
    replace: [array_param]
    new_param: new_value
    array_param:
        sub_array_param4: value4

# Acme\Bundle\SecondBundle\Resources\config\acme.yml

acme_config_base:
    param: replaced_value
    array_param:
        sub_array_param3: value3

Result:

acme_config_base:
    param: replaced_value
    array_param:
        sub_array_param1: value1
        sub_array_param2: value2
        sub_array_param3: value3

acme_config:
    param: replaced_value
    array_param:
        sub_array_param4: value4
    new_param: new_value