How to Simplify Configuration of Multiple Bundles
When building reusable and extensible applications, developers are often faced with a choice: either create a single large bundle or multiple smaller bundles. Creating a single bundle has the drawback that it's impossible for users to remove unused functionality. Creating multiple bundles has the drawback that configuration becomes more tedious and settings often need to be repeated for various bundles.
It is possible to remove the disadvantage of the multiple bundle approach by
enabling a single Extension to prepend the settings for any bundle. It can use
the settings defined in the config/* files to prepend settings just as if
they had been written explicitly by the user in the application configuration.
For example, this could be used to configure the entity manager name to use in multiple bundles. Or it can be used to enable an optional feature that depends on another bundle being loaded as well.
To give an Extension the power to do this, it needs to implement PrependExtensionInterface:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
// src/Acme/HelloBundle/DependencyInjection/AcmeHelloExtension.php
namespace Acme\HelloBundle\DependencyInjection;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Extension\PrependExtensionInterface;
use Symfony\Component\HttpKernel\DependencyInjection\Extension;
class AcmeHelloExtension extends Extension implements PrependExtensionInterface
{
// ...
public function prepend(ContainerBuilder $container): void
{
// ...
}
}Inside the prepend()
method, developers have full access to the ContainerBuilder
instance just before the load()
method is called on each of the registered bundle Extensions. In order to
prepend settings to a bundle extension developers can use the
prependExtensionConfig()
method on the ContainerBuilder
instance. As this method only prepends settings, any other settings done explicitly
inside the config/* files would override these prepended settings.
The following example illustrates how to prepend a configuration setting in multiple bundles as well as disable a flag in multiple bundles in case a specific other bundle is not registered:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
// src/Acme/HelloBundle/DependencyInjection/AcmeHelloExtension.php
public function prepend(ContainerBuilder $container): void
{
// get all bundles
$bundles = $container->getParameter('kernel.bundles');
// determine if AcmeGoodbyeBundle is registered
if (!isset($bundles['AcmeGoodbyeBundle'])) {
// disable AcmeGoodbyeBundle in bundles
$config = ['use_acme_goodbye' => false];
foreach ($container->getExtensions() as $name => $extension) {
match ($name) {
// set use_acme_goodbye to false in the config of
// acme_something and acme_other
//
// note that if the user manually configured
// use_acme_goodbye to true in config/services.yaml
// then the setting would in the end be true and not false
'acme_something', 'acme_other' => $container->prependExtensionConfig($name, $config),
default => null
};
}
}
// get the configuration of AcmeHelloExtension (it's a list of configuration)
$configs = $container->getExtensionConfig($this->getAlias());
// iterate in reverse to preserve the original order after prepending the config
foreach (array_reverse($configs) as $config) {
// check if entity_manager_name is set in the "acme_hello" configuration
if (isset($config['entity_manager_name'])) {
// prepend the acme_something settings with the entity_manager_name
$container->prependExtensionConfig('acme_something', [
'entity_manager_name' => $config['entity_manager_name'],
]);
}
}
}The above would be the equivalent of writing the following into the
config/packages/acme_something.yaml in case AcmeGoodbyeBundle is not
registered and the entity_manager_name setting for acme_hello is set to
non_default:
1 2 3 4 5 6 7 8 9
# config/packages/acme_something.yaml
acme_something:
# ...
use_acme_goodbye: false
entity_manager_name: non_default
acme_other:
# ...
use_acme_goodbye: falsePrepending Extension in the Bundle Class
You can also prepend extension configuration directly in your Bundle class if you extend from the AbstractBundle class and define the prependExtension() method:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
use Symfony\Component\HttpKernel\Bundle\AbstractBundle;
class FooBundle extends AbstractBundle
{
public function prependExtension(ContainerConfigurator $containerConfigurator, ContainerBuilder $containerBuilder): void
{
// prepend
$containerBuilder->prependExtensionConfig('framework', [
'cache' => ['prefix_seed' => 'foo/bar'],
]);
// prepend config from a file
$containerConfigurator->import('../config/packages/cache.php');
}
}Note
The prependExtension() method, like prepend(), is called only at compile time.
7.1
Starting from Symfony 7.1, calling the import()
method inside prependExtension() will prepend the given configuration.
In previous Symfony versions, this method appended the configuration.
Alternatively, you can use the prepend parameter of the
extension()
method:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
use Symfony\Component\HttpKernel\Bundle\AbstractBundle;
class FooBundle extends AbstractBundle
{
public function prependExtension(ContainerConfigurator $containerConfigurator, ContainerBuilder $containerBuilder): void
{
// ...
$containerConfigurator->extension('framework', [
'cache' => ['prefix_seed' => 'foo/bar'],
], prepend: true);
// ...
}
}7.1
The prepend parameter of the
extension()
method was added in Symfony 7.1.
More than one Bundle using PrependExtensionInterface
If there is more than one bundle that prepends the same extension and defines the same key, the bundle that is registered first will take priority: next bundles won't override this specific config setting.
