bug #37049 [Serializer] take into account the context when preserving empty array objects (xabbuh)

This PR was merged into the 4.4 branch.

Discussion
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[Serializer] take into account the context when preserving empty array objects

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | Fix #37041
| License       | MIT
| Doc PR        |

Commits
-------

98fff21140 take into account the context when preserving empty array objects

src/Symfony/Component/Serializer/Serializer.php

@@ -20,6 +20,7 @@ use Symfony\Component\Serializer\Encoder\EncoderInterface;
 use Symfony\Component\Serializer\Exception\LogicException;
 use Symfony\Component\Serializer\Exception\NotEncodableValueException;
 use Symfony\Component\Serializer\Exception\NotNormalizableValueException;
+use Symfony\Component\Serializer\Normalizer\AbstractObjectNormalizer;
 use Symfony\Component\Serializer\Normalizer\CacheableSupportsMethodInterface;
 use Symfony\Component\Serializer\Normalizer\ContextAwareDenormalizerInterface;
 use Symfony\Component\Serializer\Normalizer\ContextAwareNormalizerInterface;
@@ -157,7 +158,7 @@ class Serializer implements SerializerInterface, ContextAwareNormalizerInterface
         }
 
         if (\is_array($data) || $data instanceof \Traversable) {
-            if ($data instanceof \Countable && 0 === $data->count()) {
+            if (($context[AbstractObjectNormalizer::PRESERVE_EMPTY_OBJECTS] ?? false) === true && $data instanceof \Countable && 0 === $data->count()) {
                 return $data;
             }
 

src/Symfony/Component/Serializer/Tests/SerializerTest.php

@@ -491,6 +491,27 @@ class SerializerTest extends TestCase
         (new Serializer())->normalize(tmpfile());
     }
 
+    public function testNormalizeTransformEmptyArrayObjectToArray()
+    {
+        $serializer = new Serializer(
+          [
+              new PropertyNormalizer(),
+              new ObjectNormalizer(),
+              new ArrayDenormalizer(),
+          ],
+          [
+              'json' => new JsonEncoder(),
+          ]
+        );
+
+        $object = [];
+        $object['foo'] = new \ArrayObject();
+        $object['bar'] = new \ArrayObject(['notempty']);
+        $object['baz'] = new \ArrayObject(['nested' => new \ArrayObject()]);
+
+        $this->assertSame('{"foo":[],"bar":["notempty"],"baz":{"nested":[]}}', $serializer->serialize($object, 'json'));
+    }
+
     public function testNormalizePreserveEmptyArrayObject()
     {
         $serializer = new Serializer(