Optional doesn't work well with null

[francoism90]

Payload (request):

{
    name: 'Test',
    content: null,
}

Data object:

public function __construct(
        public string $name,
        public Optional|string $content,
    ) {
    }

Results in invalid data error. Is this intended? A workaround is to use public Optional|string|null $content or to filter null values out of the payload.

[juse-less]

I took a quick peek on this. It's definitely possible that I've missed the Optional reference somewhere.
That aside - There's a RuleInferrer for Sometimes, which checks if the property is Optional, and, if so, sets Laravels 'sometimes' rule.
From my understanding of 'sometimes', it'll skip validation if the whole attribute is missing, but use the other rules to validate it, if the attribute is present.
So it sounds like you'd need to add null as a type for it.

Depending on what you'd like to achieve, you could possibly use the Exclude rules to remove the attribute from the data, if the value is null.
Maybe something like

public static function rules(array $payload): array
{
    return [
        'content' => [Rule::excludeIf(! isset($payload['content']))],
    ];
}

as outlined in the Laravel documentation.
It could be possible to use something like Rule::excludeUnless(), as well, but it wasn't directly written in the documentation and I don't have my editor available to check right now.

Also of note, you may need to also add the Sometimes rule in that Data::rules() array, since we're overwriting rules.
Drawing blanks if one needs to or not.

Edit: So I don't forget - you may also set Optional yourself when you instantiate the class doing something like

$data['content'] ??= Optional::create();

Data::from($data);

But I'm not sure that'd actually help with the validation.
(From the Data documentation - scroll to the bottom.)

[toni-abrx]

Replying in hope it will be helpful to someone in the future.
The Optional|string type hint denotes that the property may be omitted but if it is present, it must be a string. That's why the null check fails. In case null values should be allowed, you need to type hint it like this:

public function __construct(
        public string $name,
        public Optional|string|null $content, // add null type hint here
    ) {
    }