--- /dev/null
+<?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\Component\DependencyInjection;
+
+use Psr\Container\ContainerInterface as PsrContainerInterface;
+use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
+use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
+
+/**
+ * @author Robin Chalas <robin.chalas@gmail.com>
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class ServiceLocator implements PsrContainerInterface
+{
+ private $factories;
+ private $loading = array();
+ private $externalId;
+ private $container;
+
+ /**
+ * @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[$id])) {
+ throw new ServiceNotFoundException($id, end($this->loading) ?: null, null, array(), $this->createServiceNotFoundMessage($id));
+ }
+
+ if (isset($this->loading[$id])) {
+ $ids = array_values($this->loading);
+ $ids = array_slice($this->loading, array_search($id, $ids));
+ $ids[] = $id;
+
+ throw new ServiceCircularReferenceException($id, $ids);
+ }
+
+ $this->loading[$id] = $id;
+ try {
+ return $this->factories[$id]();
+ } finally {
+ unset($this->loading[$id]);
+ }
+ }
+
+ public function __invoke($id)
+ {
+ return isset($this->factories[$id]) ? $this->get($id) : null;
+ }
+
+ /**
+ * @internal
+ */
+ public function withContext($externalId, Container $container)
+ {
+ $locator = clone $this;
+ $locator->externalId = $externalId;
+ $locator->container = $container;
+
+ return $locator;
+ }
+
+ private function createServiceNotFoundMessage($id)
+ {
+ if ($this->loading) {
+ return sprintf('The service "%s" has a dependency on a non-existent service "%s". This locator %s', end($this->loading), $id, $this->formatAlternatives());
+ }
+
+ $class = debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT | DEBUG_BACKTRACE_IGNORE_ARGS, 3);
+ $class = isset($class[2]['object']) ? get_class($class[2]['object']) : null;
+ $externalId = $this->externalId ?: $class;
+
+ $msg = sprintf('Service "%s" not found: ', $id);
+
+ if (!$this->container) {
+ $class = null;
+ } elseif ($this->container->has($id) || isset($this->container->getRemovedIds()[$id])) {
+ $msg .= 'even though it exists in the app\'s container, ';
+ } else {
+ try {
+ $this->container->get($id);
+ $class = null;
+ } catch (ServiceNotFoundException $e) {
+ if ($e->getAlternatives()) {
+ $msg .= sprintf(' did you mean %s? Anyway, ', $this->formatAlternatives($e->getAlternatives(), 'or'));
+ } else {
+ $class = null;
+ }
+ }
+ }
+ if ($externalId) {
+ $msg .= sprintf('the container inside "%s" is a smaller service locator that %s', $externalId, $this->formatAlternatives());
+ } else {
+ $msg .= sprintf('the current service locator %s', $this->formatAlternatives());
+ }
+
+ if (!$class) {
+ // no-op
+ } elseif (is_subclass_of($class, ServiceSubscriberInterface::class)) {
+ $msg .= sprintf(' Unless you need extra laziness, try using dependency injection instead. Otherwise, you need to declare it using "%s::getSubscribedServices()".', preg_replace('/([^\\\\]++\\\\)++/', '', $class));
+ } else {
+ $msg .= 'Try using dependency injection instead.';
+ }
+
+ return $msg;
+ }
+
+ private function formatAlternatives(array $alternatives = null, $separator = 'and')
+ {
+ $format = '"%s"%s';
+ if (null === $alternatives) {
+ if (!$alternatives = array_keys($this->factories)) {
+ return 'is empty...';
+ }
+ $format = sprintf('only knows about the %s service%s.', $format, 1 < count($alternatives) ? 's' : '');
+ }
+ $last = array_pop($alternatives);
+
+ return sprintf($format, $alternatives ? implode('", "', $alternatives) : $last, $alternatives ? sprintf(' %s "%s"', $separator, $last) : '');
+ }
+}