[DI][Contracts] add and implement ServiceProviderInterface

Author: mateuszsip

CHANGELOG.md

@@ -6,6 +6,7 @@ CHANGELOG
 
  * added `HttpClient` namespace with contracts for implementing flexible HTTP clients
  * added `EventDispatcher\EventDispatcherInterface`
+ * added `ServiceProviderInterface`
 
 1.0.0
 -----

Service/ServiceLocatorTrait.php

@@ -15,7 +15,7 @@
 use Psr\Container\NotFoundExceptionInterface;
 
 /**
- * A trait to help implement PSR-11 service locators.
+ * A trait to help implement ServiceProviderInterface.
  *
  * @author Robin Chalas <robin.chalas@gmail.com>
  * @author Nicolas Grekas <p@tchwork.com>
@@ -24,6 +24,7 @@ trait ServiceLocatorTrait
 {
     private $factories;
     private $loading = [];
+    private $providedTypes;
 
     /**
      * @param callable[] $factories
@@ -66,6 +67,28 @@ public function get($id)
         }
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function getProvidedServices(): array
+    {
+        if (null === $this->providedTypes) {
+            $this->providedTypes = [];
+
+            foreach ($this->factories as $name => $factory) {
+                if (!\is_callable($factory)) {
+                    $this->providedTypes[$name] = '?';
+                } else {
+                    $type = (new \ReflectionFunction($factory))->getReturnType();
+
+                    $this->providedTypes[$name] = $type ? ($type->allowsNull() ? '?' : '').$type->getName() : '?';
+                }
+            }
+        }
+
+        return $this->providedTypes;
+    }
+
     private function createNotFoundException(string $id): NotFoundExceptionInterface
     {
         if (!$alternatives = array_keys($this->factories)) {

Service/ServiceProviderInterface.php

@@ -0,0 +1,36 @@
+<?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\ContainerInterface;
+
+/**
+ * A ServiceProviderInterface exposes the identifiers and the types of services provided by a container.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ * @author Mateusz Sip <mateusz.sip@gmail.com>
+ */
+interface ServiceProviderInterface extends ContainerInterface
+{
+    /**
+     * Returns an associative array of service types keyed by the identifiers provided by the current container.
+     *
+     * Examples:
+     *
+     *  * ['logger' => 'Psr\Log\LoggerInterface'] means the object provides a service named "logger" that implements Psr\Log\LoggerInterface
+     *  * ['foo' => '?'] means the container provides service name "foo" of unspecified type
+     *  * ['bar' => '?Bar\Baz'] means the container provides a service "bar" of type Bar\Baz|null
+     *
+     * @return string[] The provided service types, keyed by service names
+     */
+    public function getProvidedServices(): array;
+}