Custom Types

[sinclairzx81]

This PR implements custom types for TypeBox. These types allow implementers to create highly specialized validation rules for data that cannot be expressed via JSON schema.

Custom types have been written to integrate with the TypeBox TypeCompiler, Value and Error modules, however custom error reporting is limited to report there was a problem validating the custom type. This may be expanded upon in subsequent revisions.

Example

import { Type, Kind } from '@sinclair/typebox'
import { Custom } from '@sinclair/typebox/custom'

// Ensure the type is registered first
Custom.Set('BigInt', value => typeof value === 'bigint')

// Create a type with the [Kind]: 'BigInt' to match registered type.
const T = Type.Unsafe<bigint>({ [Kind]: 'BigInt' })  // const T = { [Kind]: 'BigInt' }

// Check values as per usual
const R = Value.Check(T, 65536n)                     // const R = true

To implement a custom type. The symbol property [Kind] is required. The string value given to this property is should match the string argument passed to Custom.Set(...).