bug #25529 [Validator] Fix access to root object when using composite constraint (ostrolucky)

This PR was merged into the 2.7 branch.

Discussion
----------

[Validator] Fix access to root object when using composite constraint

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12315, #20477, #21706
| License       | MIT
| Doc PR        |

Commits
-------

b18cdcf417 [Validator] Fix access to root object when using composite constraint

src/Symfony/Component/Validator/Tests/Validator/Abstract2Dot5ApiTest.php

@@ -13,6 +13,7 @@ namespace Symfony\Component\Validator\Tests\Validator;
 
 use Symfony\Component\Validator\Constraints\Callback;
 use Symfony\Component\Validator\Constraints\Collection;
+use Symfony\Component\Validator\Constraints\Expression;
 use Symfony\Component\Validator\Constraints\GroupSequence;
 use Symfony\Component\Validator\Constraints\NotNull;
 use Symfony\Component\Validator\Constraints\Traverse;
@@ -648,6 +649,7 @@ abstract class Abstract2Dot5ApiTest extends AbstractValidatorTest
         $called = false;
         $entity = new Entity();
         $entity->firstName = 'Bernhard';
+        $entity->data = array('firstName' => 'Bernhard');
 
         $callback = function ($value, ExecutionContextInterface $context) use ($test, $entity, &$called) {
             $called = true;
@@ -656,6 +658,7 @@ abstract class Abstract2Dot5ApiTest extends AbstractValidatorTest
 
         $this->metadata->addConstraint(new Callback($callback));
         $this->metadata->addPropertyConstraint('firstName', new Callback($callback));
+        $this->metadata->addPropertyConstraint('data', new Collection(array('firstName' => new Expression('value == this.firstName'))));
 
         $this->validator->validate($entity);
 

src/Symfony/Component/Validator/Validator/RecursiveContextualValidator.php

@@ -108,7 +108,7 @@ class RecursiveContextualValidator implements ContextualValidatorInterface
 
             $this->validateGenericNode(
                 $value,
-                null,
+                $previousObject,
                 is_object($value) ? spl_object_hash($value) : null,
                 $metadata,
                 $this->defaultPropertyPath,