[Validator] UniqueValidator - normalize before reducing keys

[Brajk19]

Q	A
Branch?	6.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Issues
License	MIT

In #42403 checking for uniqueness of certain collection keys was enabled. Method UniqueValidator::reduceElementKeys removes all keys which are not specified.
Problem is that this happens before normalization, which in my opinion is not great because that method accepts array argument and if i have some object (DTO), TypeError will be thrown.

Example:

class ParentDTO
{
    /**
     * @var ChildDTO[]
     */
    #[Assert\Unique(
        normalizer: [ChildDTO::class, 'normalize']
        fields: 'id'
    )]
    public array $children;
}

class ChildDTO
{
    public string $id;
    public string $name;

    public static function normalize(self $obj): array
    {
        return [
            'id' => $obj->id,
            'name' => $obj->name
        ];
    }
}

Because normalization will happen after reduceElementKeys this will be thrown:
TypeError: Symfony\Component\Validator\Constraints\UniqueValidator::reduceElementKeys(): Argument #2 ($element) must be of type array, ...\ChildDTO given, called in .../UniqueValidator.php on line 48

If $element = $normalizer($element); is executed before reduceElementKeys it would enable using Assert\Unique with array of objects when correctly normalized

[carsonbot]

Hey!

Thanks for your PR. You are targeting branch "7.1" but it seems your PR description refers to branch "6.4".
Could you update the PR description or change target branch? This helps core maintainers a lot.

Cheers!

Carsonbot

[xabbuh]

For 5.4?

[stof]

@xabbuh the original PR was merged in 6.1

[xabbuh]

I see, this was introduced in #42403 and not in #38488.

[fabpot]

Thank you @Brajk19.