[VarDumper] Fix serialization of stubs with null or uninitialized values

Cloner/Internal/NoDefault.php

@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\VarDumper\Cloner\Internal;
+
+/**
+ * Flags a typed property that has no default value.
+ *
+ * This dummy object is used to distinguish a property with a default value of null
+ * from a property that is uninitialized by default.
+ *
+ * @internal
+ */
+enum NoDefault
+{
+    case NoDefault;
+}

Cloner/Stub.php

@@ -11,6 +11,8 @@
 
 namespace Symfony\Component\VarDumper\Cloner;
 
+use Symfony\Component\VarDumper\Cloner\Internal\NoDefault;
+
 /**
  * Represents the main properties of a PHP variable.
  *
@@ -50,15 +52,20 @@ public function __sleep(): array
         $properties = [];
 
         if (!isset(self::$defaultProperties[$c = static::class])) {
-            self::$defaultProperties[$c] = get_class_vars($c);
+            $reflection = new \ReflectionClass($c);
+            self::$defaultProperties[$c] = [];
+
+            foreach ($reflection->getProperties() as $p) {
+                if ($p->isStatic()) {
+                    continue;
+                }
 
-            foreach ((new \ReflectionClass($c))->getStaticProperties() as $k => $v) {
-                unset(self::$defaultProperties[$c][$k]);
+                self::$defaultProperties[$c][$p->name] = $p->hasDefaultValue() ? $p->getDefaultValue() : ($p->hasType() ? NoDefault::NoDefault : null);
             }
         }
 
         foreach (self::$defaultProperties[$c] as $k => $v) {
-            if ($this->$k !== $v) {
+            if (NoDefault::NoDefault === $v || $this->$k !== $v) {
                 $properties[] = $k;
             }
         }

Tests/Cloner/StubTest.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\VarDumper\Tests\Cloner;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\VarDumper\Cloner\Stub;
+
+final class StubTest extends TestCase
+{
+    public function testUnserializeNullValue()
+    {
+        $stub = new Stub();
+        $stub->value = null;
+
+        $stub = unserialize(serialize($stub));
+
+        self::assertNull($stub->value);
+    }
+
+    public function testUnserializeNullInTypedProperty()
+    {
+        $stub = new MyStub();
+        $stub->myProp = null;
+
+        $stub = unserialize(serialize($stub));
+
+        self::assertNull($stub->myProp);
+    }
+
+    public function testUninitializedStubPropertiesAreLeftUninitialized()
+    {
+        $stub = new MyStub();
+
+        $stub = unserialize(serialize($stub));
+
+        $r = new \ReflectionProperty(MyStub::class, 'myProp');
+        self::assertFalse($r->isInitialized($stub));
+    }
+}
+
+final class MyStub extends Stub
+{
+    public mixed $myProp;
+}