Convert empty string to null when passed to type: null|DateTimeImmutable

[eigan]

I have an input field in the frontend that renders a datepicker:

<input type="text" name="date">

I want to map this value to null|\DateTimeImmutable.

The issue is that when the HTTP request is submitted via <form> (not js/fetch), an empty date field is simply just an empty string. Because of that, I currently have to use:

''|\DateTimeImmutable

instead of:

null|\DateTimeImmutable

Is there a good solution that would allow me to use null|\DateTimeImmutable as the type?

I tried creating a custom constructor, but this syntax was not allowed:

registerConstructor(function (string $value): \DateTimeImmutable|null {
    if (empty($value)) {
        return null;
    }

    return DateUtils::parseDate($value);
});

This results in the following error:

Invalid return type `DateTimeImmutable|null` for constructor

My current solution is to force null or the value inside the method like

$payload['date'] = $payload['date'] ?? null ?: null;

[eigan]

Maybe what iam looking for is allowScalarValueCasting to support '' -> null.
I already need to use allowScalarValueCasting for casting a <select> value into int. 🤔

EDIT:
Looks like this is possible. Though have to provide my own date parser.

->registerConverter(function (string $value): \DateTimeImmutable|null {
    if ($value === '') {
        return null;
    }

    return DateUtils::parseDate($value);
})
->registerConverter(function (string $value): int|null {
    if ($value === '') {
        return null;
    }

    return (int) $value;
})

[romm]

Hi @eigan, converters are indeed the proper solution. You can use it this way:

(new MapperBuilder())
    ->registerConverter(static function (string $value, callable $next): DateTimeInterface|null {
        return $value === '' ? null : $next($value);
    })
    ->mapper()
    ->map(…);

Hope this solves your issue 😊