JSON Schema builder and hydrator

\TYPO3\CMS\Core\JsonSchema\SchemaBuilder creates the JSON Schema of actions. You can also use it alone, to describe PHP types for external systems. It creates an immutable \TYPO3\CMS\Core\JsonSchema\Schema from a PHP type of symfony/type-info. It supports scalars, lists, maps, array shapes, unions, intersections, enums, implementations of \DateTimeInterface, data objects with their promoted constructor properties, and generic data objects with @template annotations. A \TYPO3\CMS\Core\JsonSchema\SchemaStore collects the definitions of objects, and a schema refers to them with $ref. This allows circular structures.

\TYPO3\CMS\Core\JsonSchema\Hydrator uses such a schema to change raw data, for example from json_decode(), into the described PHP values. This includes enums, \DateTimeImmutable instances and data objects.

use Symfony\Component\TypeInfo\Type;
use TYPO3\CMS\Core\JsonSchema\Hydrator;
use TYPO3\CMS\Core\JsonSchema\SchemaBuilder;

final readonly class Coordinates
{
    public function __construct(
        public float $latitude,
        public float $longitude,
        public ?string $label = null,
    ) {}
}

$schema = (new SchemaBuilder())->build(Type::object(Coordinates::class));

// Expose the schema to an external system
$json = json_encode($schema);

// Hydrate raw input data based on the schema
$coordinates = (new Hydrator())->hydrate(
    json_decode('{"latitude": 50.9, "longitude": 6.9}'),
    $schema,
);

The PHP attributes \TYPO3\CMS\Core\Attribute\Serialization\IntersectWithParent and \TYPO3\CMS\Core\Attribute\Serialization\DynamicSerializationSchema control how a schema shows nested data objects. With \TYPO3\CMS\Core\JsonSchema\DynamicSchemaProviderInterface, you can supply schemas that TYPO3 knows only at runtime.