Union type with scalar types and Data class not possible?

[ragulka]

It seems that union types that include a Data class will always try to normalize the other type into Data. The following throws an error:

Could not create a `App\Data\TaxData` object from value with type `integer`, no normalizer was found.

class OrderItem extends Data
{
    public function __construct(
        // either the tax rate object, or it's ID
        public int|TaxData $tax, 
        // ... other properties
    ) {}
}

I would expect that if int is an accepted type, and if the passed value is an int, this package would not try to cast it into the TaxData object.

I understand that I can use a custom cast, or even load the model and cast it to TaxData in the constructor, but given that there may be 100s of OrderItems for a single order, it may mean that the same Tax models is loaded 100s of times from the DB. Instead, I'd like to skip loading the Tax models when receiving input from frontend, and only use TaxData when sending the data to the frontend.

Any thoughts?

[rubenvanassche]

Technically we don't support union types, in versions before v4 we even let data throw an exception when an union type was used, that restriction was removed because I think in future versions we want to support this. But it is quite complicated since we need to rethink the casting, transforming, validation process.

The problem lies here:

laravel-data/src/DataPipes/CastPropertiesDataPipe.php

Lines 84 to 93 in 7eda411

	if (
	$property->type->kind->isDataObject()
	|| $property->type->kind->isDataCollectable()
	) {
	$context = $creationContext->next($property->type->dataClass, $property->name);
	return $property->type->kind->isDataObject()
	? $context->from($value)
	: $context->collect($value, $property->type->iterableClass);
	}

Since we allow data objects to be constructed from anything: arrays, strings, int's it is quite difficult to decide what should happen in this case. A MoneyData object could be totally valid to be constructed from a single int. We could check if a magic constructor exists for the property value but that would probably cost a lot of time.

What we could do, is trying to create the data object and if it fails just use the value. I've implemented this but it will not work with collectables since that's a whole other story. (6075b43)