bug #23468 [DI] Handle root namespace in service definitions (ro0NL)

This PR was squashed before being merged into the 2.7 branch (closes #23468).

Discussion
----------

[DI] Handle root namespace in service definitions

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #... <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!--highly recommended for new features-->

Fixes

```
Cannot dump definition because of invalid class name ('\\stdClass')
```

for

```yaml
services:
    foo: {class: '\stdClass' }
```

`ContainerBuilder` allows it, so `PhpDumper` should as well.

Commits
-------

05170c8 [DI] Handle root namespace in service definitions

src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php

@@ -377,15 +377,9 @@ private function addServiceReturn($id, $definition)
      */
     private function addServiceInstance($id, Definition $definition)
     {
-        $class = $definition->getClass();
-
-        if ('\\' === substr($class, 0, 1)) {
-            $class = substr($class, 1);
-        }
-
-        $class = $this->dumpValue($class);
+        $class = $this->dumpValue($definition->getClass());
 
-        if (0 === strpos($class, "'") && !preg_match('/^\'[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
+        if (0 === strpos($class, "'") && !preg_match('/^\'(?:\\\{2})?[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(?:\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
             throw new InvalidArgumentException(sprintf('"%s" is not a valid class name for the "%s" service.', $class, $id));
         }
 
@@ -1440,11 +1434,13 @@ private function dumpLiteralClass($class)
         if (false !== strpos($class, '$')) {
             throw new RuntimeException('Cannot dump definitions which have a variable class name.');
         }
-        if (0 !== strpos($class, "'") || !preg_match('/^\'[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
+        if (0 !== strpos($class, "'") || !preg_match('/^\'(?:\\\{2})?[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(?:\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
             throw new RuntimeException(sprintf('Cannot dump definition because of invalid class name (%s)', $class ?: 'n/a'));
         }
 
-        return '\\'.substr(str_replace('\\\\', '\\', $class), 1, -1);
+        $class = substr(str_replace('\\\\', '\\', $class), 1, -1);
+
+        return 0 === strpos($class, '\\') ? $class : '\\'.$class;
     }
 
     /**

src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php

@@ -339,4 +339,17 @@ public function testCircularReferenceAllowanceForInlinedDefinitionsForLazyServic
 
         $this->addToAssertionCount(1);
     }
+
+    public function testDumpHandlesLiteralClassWithRootNamespace()
+    {
+        $container = new ContainerBuilder();
+        $container->register('foo', '\\stdClass');
+
+        $dumper = new PhpDumper($container);
+        eval('?>'.$dumper->dump(array('class' => 'Symfony_DI_PhpDumper_Test_Literal_Class_With_Root_Namespace')));
+
+        $container = new \Symfony_DI_PhpDumper_Test_Literal_Class_With_Root_Namespace();
+
+        $this->assertInstanceOf('stdClass', $container->get('foo'));
+    }
 }