bug symfony#61036 [ObjectMapper] Correctly manage constructor initialization (alanpoulain)

This PR was merged into the 7.3 branch.

Discussion
----------

[ObjectMapper] Correctly manage constructor initialization

| Q             | A
| ------------- | ---
| Branch?       | 7.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix symfony#60797 Fix symfony#60807
| License       | MIT

Currently the ObjectMapper cannot support empty constructor initialization, which is particularly useful for Doctrine collections:

```php
class Article
{
    #[ORM\ManyToMany(targetEntity: Tag::class)]
    private Collection $tags;

    public function __construct()
    {
        $this->tags = new ArrayCollection();
    }

    public function addTag($tag)
    {
         // ...
    }

    public function removeTag($tag)
    {
         // ...
    }
}
```

This kind of error is thrown by the PropertyAccessor:

> Symfony\Component\PropertyAccess\Exception\UninitializedPropertyException: The property "Symfony\Component\ObjectMapper\Tests\Fixtures\InitializedConstructor\B::$tags" is not readable because it is typed "array". You should initialize it or declare a default value instead.

This PR fixes this but also another related issue (symfony#60807): since an "empty" (no constructor arguments) constructor is always called, the class-level transformation test does not pass anymore:

> Symfony\Component\ObjectMapper\Tests\ObjectMapperTest::testMapToWithInstanceHook
ArgumentCountError: Too few arguments to function Symfony\Component\ObjectMapper\Tests\Fixtures\InstanceCallback\B::__construct(), 0 passed in /home/workspace/symfony/symfony/src/Symfony/Component/ObjectMapper/ObjectMapper.php on line 151 and exactly 1 expected

To solve this, a check is done on `map?->transform`.

Commits
-------

38e4037 [ObjectMapper] Correctly manage constructor initialization

Author: nicolas-grekas

src/Symfony/Component/ObjectMapper/ObjectMapper.php

@@ -146,7 +146,7 @@ public function map(object $source, object|string|null $target = null): object
             }
         }
 
-        if (!$mappingToObject && $ctorArguments && $constructor) {
+        if (!$mappingToObject && !$map?->transform && $constructor) {
             try {
                 $mappedTarget->__construct(...$ctorArguments);
             } catch (\ReflectionException $e) {

src/Symfony/Component/ObjectMapper/Tests/Fixtures/InitializedConstructor/A.php

@@ -0,0 +1,17 @@
+<?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\ObjectMapper\Tests\Fixtures\InitializedConstructor;
+
+class A
+{
+    public array $tags = ['foo', 'bar'];
+}

src/Symfony/Component/ObjectMapper/Tests/Fixtures/InitializedConstructor/B.php

@@ -0,0 +1,31 @@
+<?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\ObjectMapper\Tests\Fixtures\InitializedConstructor;
+
+class B
+{
+    public array $tags;
+
+    public function __construct()
+    {
+        $this->tags = [];
+    }
+
+    public function addTag($tag)
+    {
+        $this->tags[] = $tag;
+    }
+
+    public function removeTag($tag)
+    {
+    }
+}

src/Symfony/Component/ObjectMapper/Tests/ObjectMapperTest.php

@@ -32,6 +32,8 @@
 use Symfony\Component\ObjectMapper\Tests\Fixtures\Flatten\User;
 use Symfony\Component\ObjectMapper\Tests\Fixtures\Flatten\UserProfile;
 use Symfony\Component\ObjectMapper\Tests\Fixtures\HydrateObject\SourceOnly;
+use Symfony\Component\ObjectMapper\Tests\Fixtures\InitializedConstructor\A as InitializedConstructorA;
+use Symfony\Component\ObjectMapper\Tests\Fixtures\InitializedConstructor\B as InitializedConstructorB;
 use Symfony\Component\ObjectMapper\Tests\Fixtures\InstanceCallback\A as InstanceCallbackA;
 use Symfony\Component\ObjectMapper\Tests\Fixtures\InstanceCallback\B as InstanceCallbackB;
 use Symfony\Component\ObjectMapper\Tests\Fixtures\InstanceCallbackWithArguments\A as InstanceCallbackWithArgumentsA;
@@ -147,6 +149,15 @@ public function testDeeperRecursion()
         $this->assertInstanceOf(RelationDto::class, $mapped->relation);
     }
 
+    public function testMapWithInitializedConstructor()
+    {
+        $a = new InitializedConstructorA();
+        $mapper = new ObjectMapper(propertyAccessor: PropertyAccess::createPropertyAccessor());
+        $b = $mapper->map($a, InitializedConstructorB::class);
+        $this->assertInstanceOf(InitializedConstructorB::class, $b);
+        $this->assertEquals($b->tags, ['foo', 'bar']);
+    }
+
     public function testMapToWithInstanceHook()
     {
         $a = new InstanceCallbackA();