Fat Enums: WithData exceptions and ShouldThrow sentinel

WithDataExceptions.php

<?php

// What happens when data is missing?

// 1. Missing the attribute entirely throws MissingDataAttributeException
#[WithData(['label' => 'Active'])]
case Active = 'active';

case Inactive = 'inactive'; // No attribute!

Status::Inactive->data('label');
// MissingDataAttributeException: "Status::Inactive has no WithData attribute"

// 2. Missing a key throws MissingDataKeyException
Status::Active->data('icon');
// MissingDataKeyException: "Key 'icon' not found in WithData for Status::Active"

// 3. Use defaults to suppress exceptions
Status::Active->data('icon', default: null);   // null
Status::Active->data('icon', default: 'star'); // 'star'

// How does it know null is a default vs "no default given"?
// The ShouldThrow sentinel pattern:

class ShouldThrow
{
    private function __construct() {}
}

public function data(string $key, mixed $default = new ShouldThrow): mixed
{
    // If $default is still ShouldThrow, no default was passed
    if ($default instanceof ShouldThrow) {
        throw new MissingDataKeyException(...);
    }
    return $default;
}