[Serializer] Skip uninitialized (PHP 7.4) properties in PropertyNormalizer and ObjectNormalizer

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

@@ -83,8 +83,14 @@ class ObjectNormalizer extends AbstractObjectNormalizer
             }
         }
 
+        $checkPropertyInitialization = \PHP_VERSION_ID >= 70400;
+
         // properties
         foreach ($reflClass->getProperties(\ReflectionProperty::IS_PUBLIC) as $reflProperty) {
+            if ($checkPropertyInitialization && !$reflProperty->isInitialized($object)) {
+                continue;
+            }
+
             if ($reflProperty->isStatic() || !$this->isAllowedAttribute($object, $reflProperty->name, $format, $context)) {
                 continue;
             }

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

@@ -99,9 +99,20 @@ class PropertyNormalizer extends AbstractObjectNormalizer
     {
         $reflectionObject = new \ReflectionObject($object);
         $attributes = [];
+        $checkPropertyInitialization = \PHP_VERSION_ID >= 70400;
 
         do {
             foreach ($reflectionObject->getProperties() as $property) {
+                if ($checkPropertyInitialization) {
+                    if (!$property->isPublic()) {
+                        $property->setAccessible(true);
+                    }
+
+                    if (!$property->isInitialized($object)) {
+                        continue;
+                    }
+                }
+
                 if (!$this->isAllowedAttribute($reflectionObject->getName(), $property->name, $format, $context)) {
                     continue;
                 }

src/Symfony/Component/Serializer/Tests/Fixtures/Php74Dummy.php

@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Serializer\Tests\Fixtures;
+
+/**
+ * @author Valentin Udaltsov <udaltsov.valentin@gmail.com>
+ */
+final class Php74Dummy
+{
+    public string $uninitializedProperty;
+
+    public string $initializedProperty = 'defaultValue';
+}

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

@@ -28,6 +28,7 @@ use Symfony\Component\Serializer\SerializerInterface;
 use Symfony\Component\Serializer\Tests\Fixtures\CircularReferenceDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\GroupDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\MaxDepthDummy;
+use Symfony\Component\Serializer\Tests\Fixtures\Php74Dummy;
 use Symfony\Component\Serializer\Tests\Fixtures\SiblingHolder;
 
 /**
@@ -81,6 +82,18 @@ class ObjectNormalizerTest extends TestCase
         );
     }
 
+    /**
+     * @requires PHP 7.4
+     */
+    public function testNormalizeObjectWithUninitializedProperties()
+    {
+        $obj = new Php74Dummy();
+        $this->assertEquals(
+            ['initializedProperty' => 'defaultValue'],
+            $this->normalizer->normalize($obj, 'any')
+        );
+    }
+
     public function testDenormalize()
     {
         $obj = $this->normalizer->denormalize(

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

@@ -22,6 +22,7 @@ use Symfony\Component\Serializer\SerializerInterface;
 use Symfony\Component\Serializer\Tests\Fixtures\GroupDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\GroupDummyChild;
 use Symfony\Component\Serializer\Tests\Fixtures\MaxDepthDummy;
+use Symfony\Component\Serializer\Tests\Fixtures\Php74Dummy;
 use Symfony\Component\Serializer\Tests\Fixtures\PropertyCircularReferenceDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\PropertySiblingHolder;
 
@@ -55,6 +56,18 @@ class PropertyNormalizerTest extends TestCase
         );
     }
 
+    /**
+     * @requires PHP 7.4
+     */
+    public function testNormalizeObjectWithUninitializedProperties()
+    {
+        $obj = new Php74Dummy();
+        $this->assertEquals(
+            ['initializedProperty' => 'defaultValue'],
+            $this->normalizer->normalize($obj, 'any')
+        );
+    }
+
     public function testDenormalize()
     {
         $obj = $this->normalizer->denormalize(