Symfony version(s) affected

7.3.0

Description

While checking out #60797 and writing a fix for it, I ran into an issue with regard to Class-Level Transformation and the InstanceCallback test case https://github.com/symfony/symfony/tree/7.3/src/Symfony/Component/ObjectMapper/Tests/Fixtures/InstanceCallback.

The documentation stats that the callback "must return a correctly initialized instance of the target class" and the example code shows a private constructor with the comment "uses a private constructor to avoid direct instantiation". The InstanceCallback, however, has a public constructor which is only not called because $ctorArguments is empty (A only has property $name and B::__constructor() expects $id, thus $ctorArguments is empty), see condition

How to reproduce

Currently, the test case passes, but when changing public ?string $name = null to a promoted property in \Symfony\Component\ObjectMapper\Tests\Fixtures\InstanceCallback\B, the test case fails:

1) Symfony\Component\ObjectMapper\Tests\ObjectMapperTest::testMapToWithInstanceHook
ArgumentCountError: Symfony\Component\ObjectMapper\Tests\Fixtures\InstanceCallback\B::__construct(): Argument #1 ($id) not passed

…/src/Symfony/Component/ObjectMapper/Tests/Fixtures/InstanceCallback/B.php:16
…//src/Symfony/Component/ObjectMapper/ObjectMapper.php:151
…//src/Symfony/Component/ObjectMapper/Tests/ObjectMapperTest.php:152

showing that the constructor would be called but is only not called in the original example due to $ctorArguments being empty.

Possible Solution

As the class-level transformation is expected to return a full initialized objects, never call the constructor of the target object in ObjectMapper if level-class transformation is used.

Alternatively, if calling the constructor is correct, the documentation could be clearer and constructor argument validation could be improved because \Symfony\Component\ObjectMapper\ObjectMapperInterface::map is not expected to throw a ArgumentCountError (though only catching \ReflectionException here might be an issue on its own?).

Additional Context

No response