[Contracts] Add traits+interfaces from the DI component

src/Symfony/Component/DependencyInjection/Tests/Compiler/RegisterServiceSubscribersPassTest.php

@@ -22,7 +22,6 @@ use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ServiceLocator;
 use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
-use Symfony\Component\DependencyInjection\ServiceSubscriberTrait;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\CustomDefinition;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\TestDefinition1;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\TestDefinition2;
@@ -31,6 +30,7 @@ use Symfony\Component\DependencyInjection\Tests\Fixtures\TestServiceSubscriber;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\TestServiceSubscriberChild;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\TestServiceSubscriberParent;
 use Symfony\Component\DependencyInjection\TypedReference;
+use Symfony\Contracts\Service\ServiceSubscriberTrait;
 
 require_once __DIR__.'/../Fixtures/includes/classes.php';
 

src/Symfony/Component/DependencyInjection/Tests/Fixtures/TestServiceSubscriberChild.php

@@ -2,7 +2,7 @@
 
 namespace Symfony\Component\DependencyInjection\Tests\Fixtures;
 
-use Symfony\Component\DependencyInjection\ServiceSubscriberTrait;
+use Symfony\Contracts\Service\ServiceSubscriberTrait;
 
 class TestServiceSubscriberChild extends TestServiceSubscriberParent
 {

src/Symfony/Component/DependencyInjection/Tests/Fixtures/TestServiceSubscriberParent.php

@@ -3,7 +3,7 @@
 namespace Symfony\Component\DependencyInjection\Tests\Fixtures;
 
 use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
-use Symfony\Component\DependencyInjection\ServiceSubscriberTrait;
+use Symfony\Contracts\Service\ServiceSubscriberTrait;
 
 class TestServiceSubscriberParent implements ServiceSubscriberInterface
 {

src/Symfony/Component/DependencyInjection/Tests/ServiceLocatorTest.php

@@ -11,52 +11,16 @@
 
 namespace Symfony\Component\DependencyInjection\Tests;
 
-use PHPUnit\Framework\TestCase;
 use Symfony\Component\DependencyInjection\Container;
-use Symfony\Component\DependencyInjection\Exception\RuntimeException;
 use Symfony\Component\DependencyInjection\ServiceLocator;
 use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
+use Symfony\Contracts\Tests\Service\ServiceLocatorTest as BaseServiceLocatorTest;
 
-class ServiceLocatorTest extends TestCase
+class ServiceLocatorTest extends BaseServiceLocatorTest
 {
-    public function testHas()
+    public function getServiceLocator(array $factories)
     {
-        $locator = new ServiceLocator(array(
-            'foo' => function () { return 'bar'; },
-            'bar' => function () { return 'baz'; },
-            function () { return 'dummy'; },
-        ));
-
-        $this->assertTrue($locator->has('foo'));
-        $this->assertTrue($locator->has('bar'));
-        $this->assertFalse($locator->has('dummy'));
-    }
-
-    public function testGet()
-    {
-        $locator = new ServiceLocator(array(
-            'foo' => function () { return 'bar'; },
-            'bar' => function () { return 'baz'; },
-        ));
-
-        $this->assertSame('bar', $locator->get('foo'));
-        $this->assertSame('baz', $locator->get('bar'));
-    }
-
-    public function testGetDoesNotMemoize()
-    {
-        $i = 0;
-        $locator = new ServiceLocator(array(
-            'foo' => function () use (&$i) {
-                ++$i;
-
-                return 'bar';
-            },
-        ));
-
-        $this->assertSame('bar', $locator->get('foo'));
-        $this->assertSame('bar', $locator->get('foo'));
-        $this->assertSame(2, $i);
+        return new ServiceLocator($factories);
     }
 
     /**
@@ -65,7 +29,7 @@ class ServiceLocatorTest extends TestCase
      */
     public function testGetThrowsOnUndefinedService()
     {
-        $locator = new ServiceLocator(array(
+        $locator = $this->getServiceLocator(array(
             'foo' => function () { return 'bar'; },
             'bar' => function () { return 'baz'; },
         ));
@@ -73,32 +37,13 @@ class ServiceLocatorTest extends TestCase
         $locator->get('dummy');
     }
 
-    /**
-     * @expectedException        \Psr\Container\NotFoundExceptionInterface
-     * @expectedExceptionMessage The service "foo" has a dependency on a non-existent service "bar". This locator only knows about the "foo" service.
-     */
-    public function testThrowsOnUndefinedInternalService()
-    {
-        $locator = new ServiceLocator(array(
-            'foo' => function () use (&$locator) { return $locator->get('bar'); },
-        ));
-
-        $locator->get('foo');
-    }
-
     /**
      * @expectedException        \Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException
      * @expectedExceptionMessage Circular reference detected for service "bar", path: "bar -> baz -> bar".
      */
     public function testThrowsOnCircularReference()
     {
-        $locator = new ServiceLocator(array(
-            'foo' => function () use (&$locator) { return $locator->get('bar'); },
-            'bar' => function () use (&$locator) { return $locator->get('baz'); },
-            'baz' => function () use (&$locator) { return $locator->get('bar'); },
-        ));
-
-        $locator->get('foo');
+        parent::testThrowsOnCircularReference();
     }
 
     /**
@@ -110,7 +55,7 @@ class ServiceLocatorTest extends TestCase
         $container = new Container();
         $container->set('foo', new \stdClass());
         $subscriber = new SomeServiceSubscriber();
-        $subscriber->container = new ServiceLocator(array('bar' => function () {}));
+        $subscriber->container = $this->getServiceLocator(array('bar' => function () {}));
         $subscriber->container = $subscriber->container->withContext('caller', $container);
 
         $subscriber->getFoo();
@@ -118,7 +63,7 @@ class ServiceLocatorTest extends TestCase
 
     public function testInvoke()
     {
-        $locator = new ServiceLocator(array(
+        $locator = $this->getServiceLocator(array(
             'foo' => function () { return 'bar'; },
             'bar' => function () { return 'baz'; },
         ));
@@ -127,20 +72,6 @@ class ServiceLocatorTest extends TestCase
         $this->assertSame('baz', $locator('bar'));
         $this->assertNull($locator('dummy'), '->__invoke() should return null on invalid service');
     }
-
-    /**
-     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
-     * @expectedExceptionMessage Invalid service "foo" required by "external-id".
-     */
-    public function testRuntimeException()
-    {
-        $locator = new ServiceLocator(array(
-            'foo' => function () { throw new RuntimeException('Invalid service ".service_locator.abcdef".'); },
-        ));
-
-        $locator = $locator->withContext('external-id', new Container());
-        $locator->get('foo');
-    }
 }
 
 class SomeServiceSubscriber implements ServiceSubscriberinterface

src/Symfony/Contracts/CHANGELOG.md

@@ -7,3 +7,6 @@ CHANGELOG
  * added `Service\ResetInterface` to provide a way to reset an object to its initial state
  * added `Translation\TranslatorInterface` and `Translation\TranslatorTrait`
  * added `Cache` contract to extend PSR-6 with tag invalidation, callback-based computation and stampede protection
+ * added `Service\ServiceSubscriberInterface` to declare the dependencies of a class that consumes a service locator
+ * added `Service\ServiceSubscriberTrait` to implement `Service\ServiceSubscriberInterface` using methods' return types
+ * added `Service\ServiceLocatorTrait` to help implement PSR-11 service locators

src/Symfony/Contracts/Service/ServiceLocatorTrait.php

@@ -0,0 +1,97 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Contracts\Service;
+
+use Psr\Container\ContainerExceptionInterface;
+use Psr\Container\NotFoundExceptionInterface;
+
+/**
+ * A trait to help implement PSR-11 service locators.
+ *
+ * @author Robin Chalas <robin.chalas@gmail.com>
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+trait ServiceLocatorTrait
+{
+    private $factories;
+    private $loading = array();
+
+    /**
+     * @param callable[] $factories
+     */
+    public function __construct(array $factories)
+    {
+        $this->factories = $factories;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function has($id)
+    {
+        return isset($this->factories[$id]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get($id)
+    {
+        if (!isset($this->factories[$id])) {
+            throw $this->createNotFoundException($id);
+        }
+
+        if (isset($this->loading[$id])) {
+            $ids = array_values($this->loading);
+            $ids = \array_slice($this->loading, array_search($id, $ids));
+            $ids[] = $id;
+
+            throw $this->createCircularReferenceException($id, $ids);
+        }
+
+        $this->loading[$id] = $id;
+        try {
+            return $this->factories[$id]($this);
+        } finally {
+            unset($this->loading[$id]);
+        }
+    }
+
+    private function createNotFoundException(string $id): NotFoundExceptionInterface
+    {
+        if (!$alternatives = array_keys($this->factories)) {
+            $message = 'is empty...';
+        } else {
+            $last = array_pop($alternatives);
+            if ($alternatives) {
+                $message = sprintf('only knows about the "%s" and "%s" services.', implode('", "', $alternatives), $last);
+            } else {
+                $message = sprintf('only knows about the "%s" service.', $last);
+            }
+        }
+
+        if ($this->loading) {
+            $message = sprintf('The service "%s" has a dependency on a non-existent service "%s". This locator %s', end($this->loading), $id, $message);
+        } else {
+            $message = sprintf('Service "%s" not found: the current service locator %s', $id, $message);
+        }
+
+        return new class($message) extends \InvalidArgumentException implements NotFoundExceptionInterface {
+        };
+    }
+
+    private function createCircularReferenceException(string $id, array $path): ContainerExceptionInterface
+    {
+        return new class(sprintf('Circular reference detected for service "%s", path: "%s".', $id, implode(' -> ', $path))) extends \RuntimeException implements ContainerExceptionInterface {
+        };
+    }
+}

src/Symfony/Contracts/Service/ServiceSubscriberInterface.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Contracts\Service;
+
+/**
+ * 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('loggers' => 'Psr\Log\LoggerInterface[]') means the objects use the "loggers" name
+     *    internally to fetch an iterable of Psr\Log\LoggerInterface instances.
+     *  * 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('loggers' => '?Psr\Log\LoggerInterface[]') denotes an optional iterable 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();
+}

src/Symfony/Contracts/Service/ServiceSubscriberTrait.php

@@ -9,7 +9,7 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\DependencyInjection;
+namespace Symfony\Contracts\Service;
 
 use Psr\Container\ContainerInterface;
 

src/Symfony/Contracts/Tests/Service/ServiceLocatorTest.php

@@ -0,0 +1,94 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Contracts\Tests\Service;
+
+use PHPUnit\Framework\TestCase;
+use Psr\Container\ContainerInterface;
+use Symfony\Contracts\Service\ServiceLocatorTrait;
+
+class ServiceLocatorTest extends TestCase
+{
+    public function getServiceLocator(array $factories)
+    {
+        return new class($factories) implements ContainerInterface {
+            use ServiceLocatorTrait;
+        };
+    }
+
+    public function testHas()
+    {
+        $locator = $this->getServiceLocator(array(
+            'foo' => function () { return 'bar'; },
+            'bar' => function () { return 'baz'; },
+            function () { return 'dummy'; },
+        ));
+
+        $this->assertTrue($locator->has('foo'));
+        $this->assertTrue($locator->has('bar'));
+        $this->assertFalse($locator->has('dummy'));
+    }
+
+    public function testGet()
+    {
+        $locator = $this->getServiceLocator(array(
+            'foo' => function () { return 'bar'; },
+            'bar' => function () { return 'baz'; },
+        ));
+
+        $this->assertSame('bar', $locator->get('foo'));
+        $this->assertSame('baz', $locator->get('bar'));
+    }
+
+    public function testGetDoesNotMemoize()
+    {
+        $i = 0;
+        $locator = $this->getServiceLocator(array(
+            'foo' => function () use (&$i) {
+                ++$i;
+
+                return 'bar';
+            },
+        ));
+
+        $this->assertSame('bar', $locator->get('foo'));
+        $this->assertSame('bar', $locator->get('foo'));
+        $this->assertSame(2, $i);
+    }
+
+    /**
+     * @expectedException        \Psr\Container\NotFoundExceptionInterface
+     * @expectedExceptionMessage The service "foo" has a dependency on a non-existent service "bar". This locator only knows about the "foo" service.
+     */
+    public function testThrowsOnUndefinedInternalService()
+    {
+        $locator = $this->getServiceLocator(array(
+            'foo' => function () use (&$locator) { return $locator->get('bar'); },
+        ));
+
+        $locator->get('foo');
+    }
+
+    /**
+     * @expectedException        \Psr\Container\ContainerExceptionInterface
+     * @expectedExceptionMessage Circular reference detected for service "bar", path: "bar -> baz -> bar".
+     */
+    public function testThrowsOnCircularReference()
+    {
+        $locator = $this->getServiceLocator(array(
+            'foo' => function () use (&$locator) { return $locator->get('bar'); },
+            'bar' => function () use (&$locator) { return $locator->get('baz'); },
+            'baz' => function () use (&$locator) { return $locator->get('bar'); },
+        ));
+
+        $locator->get('foo');
+    }
+}

src/Symfony/Contracts/Tests/Service/ServiceSubscriberTraitTest.php

@@ -9,26 +9,28 @@
  * file that was distributed with this source code.
  */
 
-namespace Symfony\Component\DependencyInjection\Tests;
+namespace Symfony\Contracts\Tests\Service;
 
 use PHPUnit\Framework\TestCase;
 use Psr\Container\ContainerInterface;
-use Symfony\Component\DependencyInjection\Container;
-use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
-use Symfony\Component\DependencyInjection\ServiceSubscriberTrait;
+use Symfony\Contracts\Service\ServiceLocatorTrait;
+use Symfony\Contracts\Service\ServiceSubscriberInterface;
+use Symfony\Contracts\Service\ServiceSubscriberTrait;
 
 class ServiceSubscriberTraitTest extends TestCase
 {
     public function testMethodsOnParentsAndChildrenAreIgnoredInGetSubscribedServices()
     {
-        $expected = array(TestService::class.'::aService' => '?Symfony\Component\DependencyInjection\Tests\Service2');
+        $expected = array(TestService::class.'::aService' => '?Symfony\Contracts\Tests\Service\Service2');
 
         $this->assertEquals($expected, ChildTestService::getSubscribedServices());
     }
 
     public function testSetContainerIsCalledOnParent()
     {
-        $container = new Container();
+        $container = new class(array()) implements ContainerInterface {
+            use ServiceLocatorTrait;
+        };
 
         $this->assertSame($container, (new TestService())->setContainer($container));
     }

src/Symfony/Contracts/composer.json

@@ -18,8 +18,12 @@
     "require": {
         "php": "^7.1.3"
     },
+    "require-dev": {
+        "psr/container": "^1.0"
+    },
     "suggest": {
-        "psr/cache": "When using the Cache contract"
+        "psr/cache": "When using the Cache contracts",
+        "psr/container": "When using the Service contracts"
     },
     "autoload": {
         "psr-4": { "Symfony\\Contracts\\": "" },