"Omittable" properties (in contrast to Optional)

[maxanstey-acquire]

Hi there,

I'd like a way of creating partial DTOs whereby if a property is passed as null (or missing entirely) and its DTO property has an "Ommitable" attribute, then it is not set against the DTO at all. The important distinction here (as I'm sure you already understand) becomes clear when we think about a user DTO:

#[MapName(SnakeCaseMapper::class)]
class UserData extends Dto
{
    public function __construct(
        #[Exists(TableName::USERS->value)]
        public readonly int $id,
        public readonly string|null $name,
        public readonly string|null $email,
        public readonly DateTime|null $deletedAt,

Here we have a DTO with a nullable $name, $email, and $deletedAt -- however the only column that is actually allowed to be null in the DB is deleted_at; we have no distinction between "missing" values and "null" values.

Now we could use optional properties for this, but I don't love casting it to another class that developers will need to handle manually all over the place. What I'd rather have is a design whereby developers assume their DTO has what they need in it (the calling code should ensure e.g. the service method is passed the correctly hydrated DTO) and an error is thrown should that not happen for any reason.

Here's a simple mockup of the intended behaviour: https://pastebin.com/8zSEkx5m

Below is my attempt at using a pipeline, before I decided I'd ask you before hacking around:

public function handle(
        mixed $payload,
        DataClass $class,
        array $properties,
        CreationContext $creationContext
    ): array {
        $isSnakeCaseMapped = $class->attributes->contains(fn ($attr) => $attr instanceof SnakeCaseMapper);

        foreach ($class->properties as $property) {
            if (!$property->attributes) {
                continue;
            }

            if ($property->attributes->contains(fn ($attr) => $attr instanceof OmitIfNull)) {
                // Don't set the property against the DTO all; this isn't working at the moment. Probably need a way of modifying $payload instead?
                unset($properties[$property->name]);

                if ($isSnakeCaseMapped) {
                    // I don't like this at all. Is there a better way using laravel-data's internals?
                    unset($properties[Str::snake($property->name)]);
                }
            }
        }

        return $properties;
    }

What do you think? I'm more than happy to have a proper chat about this and if you think it's something that'd add value to the library I'd gladly put a PR together.

Thanks

Max

[maxanstey-acquire]

Or perhaps even it's possible to simply hook something in that says something like:

// This would exist somewhere internally triggered by a core attr, or hooked in, to be ran on __get? Sounds messy but you get the idea!
private function getProperty(string $property): mixed
{
    $value = $this->{$property};

    if ($value instanceof Optional) {
        throw new Something();
    }

    return $value;
}

to avoid implementing a brand new feature for something relatively similar to Optional properties?