Decorate all services that implement the same interface by default? - symfony

Question

I have a growing number of service classes that share a common interface (let's say BarService and BazService, that implement FooInterface).
All of these need to be decorated with the same decorator. Reading the docs, I know that I can do:
services:
App\BarDecorator:
# overrides the App\BarService service
decorates: App\BarService
Since I have to use the same decorator for different services I guess I would need to do:
services:
bar_service_decorator:
class: App\BarDecorator
# overrides the App\BarService service
decorates: App\BarService
baz_service_decorator:
class: App\BarDecorator
# overrides the App\BazService service
decorates: App\BazService
Problem is: this gets repetitive, quickly. And every time a new implementation of FooInterface is created, another set needs to be added to the configuration.
How can I declare that I want to decorate all services that implement FooInterface automatically, without having to declare each one individually?

Answer 1

A compiler pass allows to modify the container programmatically, to alter service definitions or add new ones.
First you'll need a way to locate all implementations of FooInterface. You can do this with the help of autoconfigure:
services:
_instanceof:
App\FooInterface:
tags: ['app.bar_decorated']
Then you'll need to create the compiler pass that collects all FooServices and creates a new decorated definition:
// src/DependencyInjection/Compiler/FooInterfaceDecoratorPass.php
namespace App\DependencyInjection\Compiler;
use App\BarDecorator;
use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
class FooInterfaceDecoratorPass implements CompilerPassInterface
{
public function process(ContainerBuilder $container)
{
if (!$container->has(BarDecorator::class)) {
// If the decorator isn't registered in the container you could register it here
return;
}
$taggedServices = $container->findTaggedServiceIds('app.bar_decorated');
foreach ($taggedServices as $id => $tags) {
// skip the decorator, we do it's not self-decorated
if ($id === BarDecorator::class) {
continue;
}
$decoratedServiceId = $this->generateAliasName($id);
// Add the new decorated service.
$container->register($decoratedServiceId, BarDecorator::class)
->setDecoratedService($id)
->setPublic(true)
->setAutowired(true);
}
}
/**
* Generate a snake_case service name from the service class name
*/
private function generateAliasName($serviceName)
{
if (false !== strpos($serviceName, '\\')) {
$parts = explode('\\', $serviceName);
$className = end($parts);
$alias = strtolower(preg_replace('/[A-Z]/', '_\\0', lcfirst($className)));
} else {
$alias = $serviceName;
}
return $alias . '_decorator';
}
}
Finally, register the compiler pass in the kernel:
// src/Kernel.php
use App\DependencyInjection\Compiler\FooInterfaceDecoratorPass;
class Kernel extends BaseKernel
{
// ...
protected function build(ContainerBuilder $container)
{
$container->addCompilerPass(new FooInterfaceDecoratorPass());
}
}

Answer 2

Interesting! I think that's going to be tricky... but maybe with some hints here you might come up with a solution that fits your needs
find all Decorators... not sure if there's an easier way in that case but I use tags for that. So create a DecoratorInterface add auto tag it...
loop through the definitions and and modify and set the decorated service
e. g. in your Kernel or AcmeAwesomeBundle do
protected function build(ContainerBuilder $container)
{
$container->registerForAutoconfiguration(DecoratorInterface::class)
->addTag('my.decorator.tag');
$decoratorIds = $container->findTaggedServiceIds('my.decorator.tag');
foreach ($decoratorIds as $decoratorId) {
$definition = $container->getDefinition($decoratorId);
$decoratedServiceId = $this->getDecoratedServiceId($definition);
$definition->setDecoratedService($decoratedServiceId);
}
}
private function getDecoratedServiceId(Definition $decoratorDefinition): string
{
// todo
// maybe u can use the arguments here
// e.g. the first arg is always the decoratedService
// might not work because the arguments are not resolved yet?
$arg1 = $decoratorDefinition->getArgument(0);
// or use a static function in your DecoratorInterface like
// public static function getDecoratedServiceId():string;
$class = $decoratorDefinition->getClass();
$decoratedServiceId = $class::getDecoratedServiceId();
return 'myDecoratedServiceId';
}
I'm pretty sure this is not complete yet but let us know how you solved it