Merge branch '4.4' into 5.0

* 4.4:
  [Mime] Remove unused var
  [HttpClient] fix monitoring timeouts when other streams are active
  [PhpUnitBridge] fix syntax on PHP 5.3
  [PhpUnitBridge] Fix undefined index when output of "composer show" cannot be parsed
  properly cascade validation to child forms
  [PhpUnitBridge] fix undefined var on version 3.4
  Move ajax clear event listener initialization on loadToolbar
  [HttpClient] Throw JsonException instead of TransportException on empty response in Response::toArray()
  take into account the context when preserving empty array objects
  [VarExporter] tfix: s/markAsSkipped/markTestSkipped/
  bumped Symfony version to 4.4.10
  updated VERSION for 4.4.9
  updated CHANGELOG for 4.4.9
  bumped Symfony version to 3.4.42
  updated VERSION for 3.4.41
  update CONTRIBUTORS for 3.4.41
  updated CHANGELOG for 3.4.41

Author: nicolas-grekas

Serializer.php

@@ -21,6 +21,7 @@
 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;
@@ -151,7 +152,7 @@ public function normalize($data, string $format = null, array $context = [])
         }
 
         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;
             }
 

Tests/SerializerTest.php

@@ -489,6 +489,27 @@ public function testNotNormalizableValueExceptionMessageForAResource()
         (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(