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feature #21708 [DI] Add and wire ServiceSubscriberInterface - aka explicit service locators (nicolas-grekas)
This PR was squashed before being merged into the 3.3-dev branch (closes #21708). Discussion ---------- [DI] Add and wire ServiceSubscriberInterface - aka explicit service locators | Q | A | ------------- | --- | Branch? | master | Bug fix? | no | New feature? | yes | BC breaks? | no | Deprecations? | no | Tests pass? | no test yet | Fixed tickets | #20658 | License | MIT | Doc PR | - This PR implements the second and missing part of #20658: it enables objects to declare their service dependencies in a similar way than we do for EventSubscribers: via a static method. Here is the interface and its current description: ```php namespace Symfony\Component\DependencyInjection; /** * A ServiceSubscriber exposes its dependencies via the static {@link getSubscribedServices} method. * * The getSubscribedServices method returns an array of service types required by such instances, * optionally keyed by the service names used internally. Service types that start with an interrogation * mark "?" are optional, while the other ones are mandatory service dependencies. * * The injected service locators SHOULD NOT allow access to any other services not specified by the method. * * It is expected that ServiceSubscriber instances consume PSR-11-based service locators internally. * This interface does not dictate any injection method for these service locators, although constructor * injection is recommended. * * @author Nicolas Grekas <p@tchwork.com> */ interface ServiceSubscriberInterface { /** * Returns an array of service types required by such instances, optionally keyed by the service names used internally. * * For mandatory dependencies: * * * array('logger' => 'Psr\Log\LoggerInterface') means the objects use the "logger" name * internally to fetch a service which must implement Psr\Log\LoggerInterface. * * array('Psr\Log\LoggerInterface') is a shortcut for * * array('Psr\Log\LoggerInterface' => 'Psr\Log\LoggerInterface') * * otherwise: * * * array('logger' => '?Psr\Log\LoggerInterface') denotes an optional dependency * * array('?Psr\Log\LoggerInterface') is a shortcut for * * array('Psr\Log\LoggerInterface' => '?Psr\Log\LoggerInterface') * * @return array The required service types, optionally keyed by service names */ public static function getSubscribedServices(); } ``` We could then have eg a controller-as-a-service implement this interface, and be auto or manually wired according to the return value of this method - using the "kernel.service_subscriber" tag to do so. eg: ```yaml services: App\Controller\FooController: arguments: [service_container] tags: - name: kernel.service_subscriber key: logger service: monolog.logger.foo_channel ``` The benefits are: - it keeps the lazy-behavior gained by service locators / container injection - it allows the referenced services to be made private from the pov of the main Symfony DIC - thus enables some compiler optimizations - it makes dependencies autowirable (while keeping manual wiring possible) - it does not add any strong coupling at the architecture level - and most importantly and contrary to regular container injection, *it makes dependencies explicit* - each classes declaring which services it consumes. Some might argue that: - it requires to be explicit - thus more verbose. Yet many others think it's a good thing - ie it's worth it. - some coupling happens at the dependency level, since you need to get the DI component to get the interface definition. This is something that the PHP-FIG could address at some point. Commits ------- c5e80a2 implement ServiceSubscriberInterface where applicable 9b7df39 [DI] Add and wire ServiceSubscriberInterface
2 parents fa36ce8 + c5e80a2 commit f99dfb0

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17 files changed

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‎src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/UnusedTagsPass.php

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@@ -24,6 +24,7 @@ class UnusedTagsPass implements CompilerPassInterface
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private $whitelist = array(
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'console.command',
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'container.service_locator',
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'container.service_subscriber',
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'config_cache.resource_checker',
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'data_collector',
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'form.type',

‎src/Symfony/Bundle/FrameworkBundle/Resources/config/session.xml

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@@ -53,14 +53,8 @@
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<service id="session_listener" class="Symfony\Component\HttpKernel\EventListener\SessionListener">
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<tag name="kernel.event_subscriber" />
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<argument type="service">
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<service class="Symfony\Component\DependencyInjection\ServiceLocator">
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<tag name="container.service_locator" />
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<argument type="collection">
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<argument key="session" type="service" id="session" on-invalid="ignore" />
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</argument>
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</service>
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</argument>
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<tag name="container.service_subscriber" id="session" />
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<argument type="service" id="container" />
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</service>
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<service id="session.save_listener" class="Symfony\Component\HttpKernel\EventListener\SaveSessionListener">

‎src/Symfony/Bundle/FrameworkBundle/Resources/config/test.xml

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<service id="test.session.listener" class="Symfony\Component\HttpKernel\EventListener\TestSessionListener">
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<tag name="kernel.event_subscriber" />
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<argument type="service">
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<service class="Symfony\Component\DependencyInjection\ServiceLocator">
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<tag name="container.service_locator" />
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<argument type="collection">
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<argument key="session" type="service" id="session" on-invalid="ignore" />
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</argument>
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</service>
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</argument>
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<tag name="container.service_subscriber" id="session" />
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<argument type="service" id="container" />
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</service>
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</services>
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</container>

‎src/Symfony/Bundle/FrameworkBundle/Routing/Router.php

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@@ -11,7 +11,9 @@
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namespace Symfony\Bundle\FrameworkBundle\Routing;
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use Symfony\Component\Config\Loader\LoaderInterface;
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use Symfony\Component\DependencyInjection\Config\ContainerParametersResource;
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use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
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use Symfony\Component\Routing\Router as BaseRouter;
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use Symfony\Component\Routing\RequestContext;
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use Symfony\Component\DependencyInjection\ContainerInterface;
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*
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* @author Fabien Potencier <fabien@symfony.com>
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*/
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class Router extends BaseRouter implements WarmableInterface
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class Router extends BaseRouter implements WarmableInterface, ServiceSubscriberInterface
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{
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private $container;
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private $collectedParameters = array();
@@ -173,4 +175,14 @@ private function resolve($value)
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return str_replace('%%', '%', $escapedValue);
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}
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/**
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* {@inheritdoc}
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*/
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public static function getSubscribedServices()
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{
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return array(
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'routing.loader' => LoaderInterface::class,
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);
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}
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}

‎src/Symfony/Bundle/TwigBundle/CacheWarmer/TemplateCacheCacheWarmer.php

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namespace Symfony\Bundle\TwigBundle\CacheWarmer;
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use Psr\Container\ContainerInterface;
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use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
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use Symfony\Component\Finder\Finder;
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use Symfony\Component\HttpKernel\CacheWarmer\CacheWarmerInterface;
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use Symfony\Bundle\FrameworkBundle\CacheWarmer\TemplateFinderInterface;
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*
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* @author Fabien Potencier <fabien@symfony.com>
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*/
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class TemplateCacheCacheWarmer implements CacheWarmerInterface
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class TemplateCacheCacheWarmer implements CacheWarmerInterface, ServiceSubscriberInterface
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{
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protected $container;
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protected $finder;
@@ -92,6 +93,16 @@ public function isOptional()
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return true;
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}
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/**
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* {@inheritdoc}
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*/
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public static function getSubscribedServices()
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{
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return array(
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'twig' => \Twig_Environment::class,
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);
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}
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/**
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* Find templates in the given directory.
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*

‎src/Symfony/Bundle/TwigBundle/Resources/config/twig.xml

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<service id="twig.cache_warmer" class="Symfony\Bundle\TwigBundle\CacheWarmer\TemplateCacheCacheWarmer" public="false">
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<tag name="kernel.cache_warmer" />
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<argument type="service" id="service_container" />
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<tag name="container.service_subscriber" id="twig" />
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<argument type="service" id="container" />
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<argument type="service" id="templating.finder" on-invalid="ignore" />
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<argument type="collection" /> <!-- Twig paths -->
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</service>

‎src/Symfony/Component/DependencyInjection/CHANGELOG.md

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3.3.0
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-----
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* added "ServiceSubscriberInterface" - to allow for per-class explicit service-locator definitions
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* added "container.service_locator" tag for defining service-locator services
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* added anonymous services support in YAML configuration files using the `!service` tag.
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* added "TypedReference" and "ServiceClosureArgument" for creating service-locator services

‎src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php

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new ResolveFactoryClassPass(),
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new FactoryReturnTypePass($resolveClassPass),
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new CheckDefinitionValidityPass(),
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new RegisterServiceSubscribersPass(),
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new ResolveNamedArgumentsPass(),
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new AutowirePass(),
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new ResolveReferencesToAliasesPass(),

‎src/Symfony/Component/DependencyInjection/Compiler/RegisterServiceSubscribersPass.php

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<?php
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/*
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* This file is part of the Symfony package.
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*
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* (c) Fabien Potencier <fabien@symfony.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Symfony\Component\DependencyInjection\Compiler;
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use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
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use Symfony\Component\DependencyInjection\ContainerInterface;
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use Symfony\Component\DependencyInjection\Definition;
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use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
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use Symfony\Component\DependencyInjection\Reference;
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use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
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use Symfony\Component\DependencyInjection\ServiceLocator;
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use Symfony\Component\DependencyInjection\TypedReference;
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/**
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* Compiler pass to register tagged services that require a service locator.
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*
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* @author Nicolas Grekas <p@tchwork.com>
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*/
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class RegisterServiceSubscribersPass extends AbstractRecursivePass
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{
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private $serviceLocator;
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protected function processValue($value, $isRoot = false)
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{
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if ($value instanceof Reference && $this->serviceLocator && 'container' === (string) $value) {
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return new Reference($this->serviceLocator);
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}
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if (!$value instanceof Definition || $value->isAbstract() || $value->isSynthetic() || !$value->hasTag('container.service_subscriber')) {
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return parent::processValue($value, $isRoot);
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}
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$serviceMap = array();
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foreach ($value->getTag('container.service_subscriber') as $attributes) {
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if (!$attributes) {
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continue;
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}
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ksort($attributes);
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if (array() !== array_diff(array_keys($attributes), array('id', 'key'))) {
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throw new InvalidArgumentException(sprintf('The "container.service_subscriber" tag accepts only the "key" and "id" attributes, "%s" given for service "%s".', implode('", "', array_keys($attributes)), $this->currentId));
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}
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if (!array_key_exists('id', $attributes)) {
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throw new InvalidArgumentException(sprintf('Missing "id" attribute on "container.service_subscriber" tag with key="%s" for service "%s".', $attributes['key'], $this->currentId));
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}
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if (!array_key_exists('key', $attributes)) {
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$attributes['key'] = $attributes['id'];
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}
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if (isset($serviceMap[$attributes['key']])) {
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continue;
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}
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$serviceMap[$attributes['key']] = new Reference($attributes['id']);
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}
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$class = $value->getClass();
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if (!is_subclass_of($class, ServiceSubscriberInterface::class)) {
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if (!class_exists($class, false)) {
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throw new InvalidArgumentException(sprintf('Class "%s" used for service "%s" cannot be found.', $class, $this->currentId));
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}
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throw new InvalidArgumentException(sprintf('Service "%s" must implement interface "%s".', $this->currentId, ServiceSubscriberInterface::class));
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}
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$this->container->addObjectResource($class);
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$subscriberMap = array();
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foreach ($class::getSubscribedServices() as $key => $type) {
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if (!is_string($type) || !preg_match('/^\??[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*+(?:\\\\[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*+)*+$/', $type)) {
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throw new InvalidArgumentException(sprintf('%s::getSubscribedServices() must return valid PHP types for service "%s" key "%s", "%s" returned.', $class, $this->currentId, $key, is_string($type) ? $type : gettype($type)));
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}
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if ($optionalBehavior = '?' === $type[0]) {
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$type = substr($type, 1);
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$optionalBehavior = ContainerInterface::IGNORE_ON_INVALID_REFERENCE;
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}
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if (is_int($key)) {
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$key = $type;
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}
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if (!isset($serviceMap[$key])) {
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$serviceMap[$key] = new Reference($type);
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}
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90+
$subscriberMap[$key] = new ServiceClosureArgument(new TypedReference((string) $serviceMap[$key], $type, $optionalBehavior ?: ContainerInterface::EXCEPTION_ON_INVALID_REFERENCE));
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unset($serviceMap[$key]);
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}
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94+
if ($serviceMap = array_keys($serviceMap)) {
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$this->container->log($this, sprintf('Service keys "%s" do not exist in the map returned by %s::getSubscribedServices() for service "%s".', implode('", "', $serviceMap), $class, $this->currentId));
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}
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$serviceLocator = $this->serviceLocator;
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$this->serviceLocator = 'container.'.$this->currentId.'.'.md5(serialize($value));
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$this->container->register($this->serviceLocator, ServiceLocator::class)
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->addArgument($subscriberMap)
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->setPublic(false)
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->setAutowired($value->isAutowired())
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->addTag('container.service_locator');
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try {
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return parent::processValue($value);
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} finally {
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$this->serviceLocator = $serviceLocator;
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}
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}
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}

‎src/Symfony/Component/DependencyInjection/ServiceSubscriberInterface.php

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<?php
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/*
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* This file is part of the Symfony package.
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*
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* (c) Fabien Potencier <fabien@symfony.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Symfony\Component\DependencyInjection;
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/**
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* A ServiceSubscriber exposes its dependencies via the static {@link getSubscribedServices} method.
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*
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* The getSubscribedServices method returns an array of service types required by such instances,
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* optionally keyed by the service names used internally. Service types that start with an interrogation
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* mark "?" are optional, while the other ones are mandatory service dependencies.
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*
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* The injected service locators SHOULD NOT allow access to any other services not specified by the method.
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*
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* It is expected that ServiceSubscriber instances consume PSR-11-based service locators internally.
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* This interface does not dictate any injection method for these service locators, although constructor
25+
* injection is recommended.
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*
27+
* @author Nicolas Grekas <p@tchwork.com>
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*/
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interface ServiceSubscriberInterface
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{
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/**
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* Returns an array of service types required by such instances, optionally keyed by the service names used internally.
33+
*
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* For mandatory dependencies:
35+
*
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* * array('logger' => 'Psr\Log\LoggerInterface') means the objects use the "logger" name
37+
* internally to fetch a service which must implement Psr\Log\LoggerInterface.
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* * array('Psr\Log\LoggerInterface') is a shortcut for
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* * array('Psr\Log\LoggerInterface' => 'Psr\Log\LoggerInterface')
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*
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* otherwise:
42+
*
43+
* * array('logger' => '?Psr\Log\LoggerInterface') denotes an optional dependency
44+
* * array('?Psr\Log\LoggerInterface') is a shortcut for
45+
* * array('Psr\Log\LoggerInterface' => '?Psr\Log\LoggerInterface')
46+
*
47+
* @return array The required service types, optionally keyed by service names
48+
*/
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public static function getSubscribedServices();
50+
}

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