.. index::
   single: Configuration; Semantic
   single: Bundle; Extension configuration

How to Create Friendly Configuration for a Bundle
=================================================

If you open your main application configuration directory (usually
``config/packages/``), you'll see a number of different files, such as
``framework.yaml``, ``twig.yaml`` and ``doctrine.yaml``. Each of these
configures a specific bundle, allowing you to define options at a high level and
then let the bundle make all the low-level, complex changes based on your
settings.

For example, the following configuration tells the FrameworkBundle to enable the
form integration, which involves the definition of quite a few services as well
as integration of other related components:

.. configuration-block::

    .. code-block:: yaml

        framework:
            form: true

    .. code-block:: xml

        <?xml version="1.0" encoding="UTF-8" ?>
        <container xmlns="http://symfony.com/schema/dic/services"
            xmlns:framework="http://symfony.com/schema/dic/symfony"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd
                http://symfony.com/schema/dic/symfony
                https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

            <framework:config>
                <framework:form/>
            </framework:config>
        </container>

    .. code-block:: php

        $container->loadFromExtension('framework', [
            'form' => true,
        ]);

Using the Bundle Extension
--------------------------

Imagine you are creating a new bundle - AcmeSocialBundle - which provides
integration with Twitter. To make your bundle configurable to the user, you
can add some configuration that looks like this:

.. configuration-block::

    .. code-block:: yaml

        # config/packages/acme_social.yaml
        acme_social:
            twitter:
                client_id: 123
                client_secret: your_secret

    .. code-block:: xml

        <!-- config/packages/acme_social.xml -->
        <?xml version="1.0" ?>
        <container xmlns="http://symfony.com/schema/dic/services"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xmlns:acme-social="http://example.org/schema/dic/acme_social"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd">

            <acme-social:config>
                <acme-social:twitter client-id="123" client-secret="your_secret"/>
            </acme-social:config>

            <!-- ... -->
        </container>

    .. code-block:: php

        // config/packages/acme_social.php
        $container->loadFromExtension('acme_social', [
            'twitter' => [
                'client_id'     => 123,
                'client_secret' => 'your_secret',
            ],
        ]);

The basic idea is that instead of having the user override individual
parameters, you let the user configure just a few, specifically created,
options. As the bundle developer, you then parse through that configuration and
load correct services and parameters inside an "Extension" class.

.. note::

    The root key of your bundle configuration (``acme_social`` in the previous
    example) is automatically determined from your bundle name (it's the
    `snake case`_ of the bundle name without the ``Bundle`` suffix ).

.. seealso::

    Read more about the extension in :doc:`/bundles/extension`.

.. tip::

    If a bundle provides an Extension class, then you should *not* generally
    override any service container parameters from that bundle. The idea
    is that if an Extension class is present, every setting that should be
    configurable should be present in the configuration made available by
    that class. In other words, the extension class defines all the public
    configuration settings for which backward compatibility will be maintained.

.. seealso::

    For parameter handling within a dependency injection container see
    :doc:`/configuration/using_parameters_in_dic`.

Processing the ``$configs`` Array
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

First things first, you have to create an extension class as explained in
:doc:`/bundles/extension`.

Whenever a user includes the ``acme_social`` key (which is the DI alias) in a
configuration file, the configuration under it is added to an array of
configurations and passed to the ``load()`` method of your extension (Symfony
automatically converts XML and YAML to an array).

For the configuration example in the previous section, the array passed to your
``load()`` method will look like this::

    [
        [
            'twitter' => [
                'client_id' => 123,
                'client_secret' => 'your_secret',
            ],
        ],
    ]

Notice that this is an *array of arrays*, not just a single flat array of the
configuration values. This is intentional, as it allows Symfony to parse several
configuration resources. For example, if ``acme_social`` appears in another
configuration file - say ``config/packages/dev/acme_social.yaml`` - with
different values beneath it, the incoming array might look like this::

    [
        // values from config/packages/acme_social.yaml
        [
            'twitter' => [
                'client_id' => 123,
                'client_secret' => 'your_secret',
            ],
        ],
        // values from config/packages/dev/acme_social.yaml
        [
            'twitter' => [
                'client_id' => 456,
            ],
        ],
    ]

The order of the two arrays depends on which one is set first.

But don't worry! Symfony's Config component will help you merge these values,
provide defaults and give the user validation errors on bad configuration.
Here's how it works. Create a ``Configuration`` class in the
``DependencyInjection`` directory and build a tree that defines the structure
of your bundle's configuration.

The ``Configuration`` class to handle the sample configuration looks like::

    // src/Acme/SocialBundle/DependencyInjection/Configuration.php
    namespace Acme\SocialBundle\DependencyInjection;

    use Symfony\Component\Config\Definition\Builder\TreeBuilder;
    use Symfony\Component\Config\Definition\ConfigurationInterface;

    class Configuration implements ConfigurationInterface
    {
        public function getConfigTreeBuilder()
        {
            $treeBuilder = new TreeBuilder('acme_social');

            $treeBuilder->getRootNode()
                ->children()
                    ->arrayNode('twitter')
                        ->children()
                            ->integerNode('client_id')->end()
                            ->scalarNode('client_secret')->end()
                        ->end()
                    ->end() // twitter
                ->end()
            ;

            return $treeBuilder;
        }
    }

.. seealso::

    The ``Configuration`` class can be much more complicated than shown here,
    supporting "prototype" nodes, advanced validation, XML-specific normalization
    and advanced merging. You can read more about this in
    :doc:`the Config component documentation </components/config/definition>`. You
    can also see it in action by checking out some core Configuration
    classes, such as the one from the `FrameworkBundle Configuration`_ or the
    `TwigBundle Configuration`_.

This class can now be used in your ``load()`` method to merge configurations and
force validation (e.g. if an additional option was passed, an exception will be
thrown)::

    // src/Acme/SocialBundle/DependencyInjection/AcmeSocialExtension.php
    public function load(array $configs, ContainerBuilder $container)
    {
        $configuration = new Configuration();

        $config = $this->processConfiguration($configuration, $configs);

        // you now have these 2 config keys
        // $config['twitter']['client_id'] and $config['twitter']['client_secret']
    }

The ``processConfiguration()`` method uses the configuration tree you've defined
in the ``Configuration`` class to validate, normalize and merge all the
configuration arrays together.

Now, you can use the ``$config`` variable to modify a service provided by your bundle.
For example, imagine your bundle has the following example config:

.. code-block:: xml

    <!-- src/Acme/SocialBundle/Resources/config/services.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd">

        <services>
            <service id="acme.social.twitter_client" class="Acme\SocialBundle\TwitterClient">
                <argument></argument> <!-- will be filled in with client_id dynamically -->
                <argument></argument> <!-- will be filled in with client_secret dynamically -->
            </service>
        </services>
    </container>

In your extension, you can load this and dynamically set its arguments::

    // src/Acme/SocialBundle/DependencyInjection/AcmeSocialExtension.php
    // ...

    use Symfony\Component\Config\FileLocator;
    use Symfony\Component\DependencyInjection\Loader\XmlFileLoader;

    public function load(array $configs, ContainerBuilder $container)
    {
        $loader = new XmlFileLoader($container, new FileLocator(dirname(__DIR__).'/Resources/config'));
        $loader->load('services.xml');

        $configuration = new Configuration();
        $config = $this->processConfiguration($configuration, $configs);

        $definition = $container->getDefinition('acme.social.twitter_client');
        $definition->replaceArgument(0, $config['twitter']['client_id']);
        $definition->replaceArgument(1, $config['twitter']['client_secret']);
    }

.. tip::

    Instead of calling ``processConfiguration()`` in your extension each time you
    provide some configuration options, you might want to use the
    :class:`Symfony\\Component\\HttpKernel\\DependencyInjection\\ConfigurableExtension`
    to do this automatically for you::

        // src/Acme/HelloBundle/DependencyInjection/AcmeHelloExtension.php
        namespace Acme\HelloBundle\DependencyInjection;

        use Symfony\Component\DependencyInjection\ContainerBuilder;
        use Symfony\Component\HttpKernel\DependencyInjection\ConfigurableExtension;

        class AcmeHelloExtension extends ConfigurableExtension
        {
            // note that this method is called loadInternal and not load
            protected function loadInternal(array $mergedConfig, ContainerBuilder $container)
            {
                // ...
            }
        }

    This class uses the ``getConfiguration()`` method to get the Configuration
    instance.

.. sidebar:: Processing the Configuration yourself

    Using the Config component is fully optional. The ``load()`` method gets an
    array of configuration values. You can instead parse these arrays yourself
    (e.g. by overriding configurations and using :phpfunction:`isset` to check
    for the existence of a value). Be aware that it'll be very hard to support XML::

        public function load(array $configs, ContainerBuilder $container)
        {
            $config = [];
            // let resources override the previous set value
            foreach ($configs as $subConfig) {
                $config = array_merge($config, $subConfig);
            }

            // ... now use the flat $config array
        }

Modifying the Configuration of Another Bundle
---------------------------------------------

If you have multiple bundles that depend on each other, it may be useful to
allow one ``Extension`` class to modify the configuration passed to another
bundle's ``Extension`` class. This can be achieved using a prepend extension.
For more details, see :doc:`/bundles/prepend_extension`.

Dump the Configuration
----------------------

The ``config:dump-reference`` command dumps the default configuration of a
bundle in the console using the Yaml format.

As long as your bundle's configuration is located in the standard location
(``YourBundle\DependencyInjection\Configuration``) and does not have
a constructor it will work automatically. If you
have something different, your ``Extension`` class must override the
:method:`Extension::getConfiguration() <Symfony\\Component\\HttpKernel\\DependencyInjection\\Extension::getConfiguration>`
method and return an instance of your ``Configuration``.

Supporting XML
--------------

Symfony allows people to provide the configuration in three different formats:
Yaml, XML and PHP. Both Yaml and PHP use the same syntax and are supported by
default when using the Config component. Supporting XML requires you to do some
more things. But when sharing your bundle with others, it is recommended that
you follow these steps.

Make your Config Tree ready for XML
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Config component provides some methods by default to allow it to correctly
process XML configuration. See ":ref:`component-config-normalization`" of the
component documentation. However, you can do some optional things as well, this
will improve the experience of using XML configuration:

Choosing an XML Namespace
~~~~~~~~~~~~~~~~~~~~~~~~~

In XML, the `XML namespace`_ is used to determine which elements belong to the
configuration of a specific bundle. The namespace is returned from the
:method:`Extension::getNamespace() <Symfony\\Component\\DependencyInjection\\Extension\\Extension::getNamespace>`
method. By convention, the namespace is a URL (it doesn't have to be a valid
URL nor does it need to exists). By default, the namespace for a bundle is
``http://example.org/schema/dic/DI_ALIAS``, where ``DI_ALIAS`` is the DI alias of
the extension. You might want to change this to a more professional URL::

    // src/Acme/HelloBundle/DependencyInjection/AcmeHelloExtension.php

    // ...
    class AcmeHelloExtension extends Extension
    {
        // ...

        public function getNamespace()
        {
            return 'http://acme_company.com/schema/dic/hello';
        }
    }

Providing an XML Schema
~~~~~~~~~~~~~~~~~~~~~~~

XML has a very useful feature called `XML schema`_. This allows you to
describe all possible elements and attributes and their values in an XML Schema
Definition (an XSD file). This XSD file is used by IDEs for auto completion and
it is used by the Config component to validate the elements.

In order to use the schema, the XML configuration file must provide an
``xsi:schemaLocation`` attribute pointing to the XSD file for a certain XML
namespace. This location always starts with the XML namespace. This XML
namespace is then replaced with the XSD validation base path returned from
:method:`Extension::getXsdValidationBasePath() <Symfony\\Component\\DependencyInjection\\Extension\\ExtensionInterface::getXsdValidationBasePath>`
method. This namespace is then followed by the rest of the path from the base
path to the file itself.

By convention, the XSD file lives in the ``Resources/config/schema/``, but you
can place it anywhere you like. You should return this path as the base path::

    // src/Acme/HelloBundle/DependencyInjection/AcmeHelloExtension.php

    // ...
    class AcmeHelloExtension extends Extension
    {
        // ...

        public function getXsdValidationBasePath()
        {
            return __DIR__.'/../Resources/config/schema';
        }
    }

Assuming the XSD file is called ``hello-1.0.xsd``, the schema location will be
``https://acme_company.com/schema/dic/hello/hello-1.0.xsd``:

.. code-block:: xml

    <!-- config/packages/acme_hello.xml -->
    <?xml version="1.0" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:acme-hello="http://acme_company.com/schema/dic/hello"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://acme_company.com/schema/dic/hello
            https://acme_company.com/schema/dic/hello/hello-1.0.xsd">

        <acme-hello:config>
            <!-- ... -->
        </acme-hello:config>

        <!-- ... -->
    </container>

.. _`FrameworkBundle Configuration`: https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php
.. _`TwigBundle Configuration`: https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php
.. _`XML namespace`: https://en.wikipedia.org/wiki/XML_namespace
.. _`XML schema`: https://en.wikipedia.org/wiki/XML_schema
.. _`snake case`: https://en.wikipedia.org/wiki/Snake_case