bug #26140 [Serializer] deserialize as a null when inner object canno…

…t be created and type hint allows null (kbkk)

This PR was squashed before being merged into the 4.1-dev branch (closes #26140).

Discussion
----------

[Serializer] deserialize as a null when inner object cannot be created and type hint allows null

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT

```php
class ObjectConstructorDummy
{
    protected $foo;
    public $bar;
    private $baz;

    public function __construct($foo, $bar, $baz)
    {
        $this->foo = $foo;
        $this->bar = $bar;
        $this->baz = $baz;
    }
}

class DummyWithNullableConstructorObject
{
    private $id;
    private $inner;

    public function __construct($id, ?ObjectConstructorDummy $inner)
    {
        $this->id = $id;
        $this->inner = $inner;
    }

    public function getId()
    {
        return $this->id;
    }

    public function getInner()
    {
        return $this->inner;
    }
}
```

Trying to deserialize to `DummyWithNullableConstructorObject` with the following data currently fails:
```php
[
    'id' => 10,
    'inner' => null
]
```

With this PR `DummyWithNullableConstructorObject ` would be constructed with `null` passed as `$inner` because of the type hint.

Commits
-------

2fe9eb1 [Serializer] deserialize as a null when inner object cannot be created and type hint allows null

src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php

@@ -351,6 +351,11 @@ protected function instantiateObject(array &$data, $class, array &$context, \Ref
                         }
                     } catch (\ReflectionException $e) {
                         throw new RuntimeException(sprintf('Could not determine the class of the parameter "%s".', $key), 0, $e);
+                    } catch (MissingConstructorArgumentsException $e) {
+                        if (!$constructorParameter->getType()->allowsNull()) {
+                            throw $e;
+                        }
+                        $parameterData = null;
                     }
 
                     // Don't run set for a parameter passed to the constructor

src/Symfony/Component/Serializer/Tests/Normalizer/ObjectNormalizerTest.php

@@ -182,6 +182,23 @@ public function testConstructorWithObjectTypeHintDenormalize()
         $this->assertEquals('rab', $obj->getInner()->bar);
     }
 
+    public function testConstructorWithUnconstructableNullableObjectTypeHintDenormalize()
+    {
+        $data = array(
+            'id' => 10,
+            'inner' => null,
+        );
+
+        $normalizer = new ObjectNormalizer();
+        $serializer = new Serializer(array($normalizer));
+        $normalizer->setSerializer($serializer);
+
+        $obj = $normalizer->denormalize($data, DummyWithNullableConstructorObject::class);
+        $this->assertInstanceOf(DummyWithNullableConstructorObject::class, $obj);
+        $this->assertEquals(10, $obj->getId());
+        $this->assertNull($obj->getInner());
+    }
+
     /**
      * @expectedException \Symfony\Component\Serializer\Exception\RuntimeException
      * @expectedExceptionMessage Could not determine the class of the parameter "unknown".
@@ -1109,3 +1126,25 @@ public function getFoo()
         return $this->Foo;
     }
 }
+
+class DummyWithNullableConstructorObject
+{
+    private $id;
+    private $inner;
+
+    public function __construct($id, ?ObjectConstructorDummy $inner)
+    {
+        $this->id = $id;
+        $this->inner = $inner;
+    }
+
+    public function getId()
+    {
+        return $this->id;
+    }
+
+    public function getInner()
+    {
+        return $this->inner;
+    }
+}