Simple validation not working

[okdewit]

Given this example DTO with a SnakeCaseMapper on output and a Max(2) validation rule:

use Spatie\LaravelData\Attributes\MapOutputName;
use Spatie\LaravelData\Attributes\Validation\Max;
use Spatie\LaravelData\Data;
use Spatie\LaravelData\Mappers\SnakeCaseMapper;

#[MapOutputName(SnakeCaseMapper::class)]
class FooDTO extends Data
{
    public function __construct(
        #[Max(2)]
        public string $fooString,
    ) {}
}

and this test code:

$foo = new FooDTO(fooString: 'too long');    // works
dump($foo->toArray());                       // output ["foo_string" => "too long"]

$foo->validate(['fooString' => 'too long']); // throws "The foo string may not be greater than 2 characters" exception

I was expecting a ValidationException to be thrown when constructing the DTO.
Calling ->validate again on the object, with the exact same data used to initialize the object seems weird.

I can of course "fix" this by adding $this->validate($this->all()); to the constructor of my DTOs:

public function __construct(
    #[Max(2)]
    public string $fooString,
) {
    $this->validate($this->all());
}

But I am curious: Am I misunderstanding the purpose of Validation attributes?

[okdewit]

I closed this because I saw there's plenty of explanations & discussion already going on elsewhere
#470