JSON schema to TypeScript type

schema-to-type.d.ts

interface SchemaTypeNames {
	'string': string;
	'boolean': boolean;
	'number': number;
	// TODO: Could we recurse for 'array' and 'object'?
	'array': any[];
	'object': unknown;
}

type Schema = {required?: any[], properties: Record<string, any>};
type NotIncluded<T, U> = T extends U ? never : T;
type Included<T, U> = T extends U ? T : never;
type RequiredParameters<S extends Schema> = {
	[k in Included<keyof S['properties'], S['required'][number]>]: SchemaTypeNames[S['properties'][k]["type"]];
}
type NotRequiredParameters<S extends Schema> = {
	[k in NotIncluded<keyof S['properties'], S['required'][number]>]?: SchemaTypeNames[S['properties'][k]["type"]];
}

/**
 * Type created from a JSON schema definition
 *
 * Note that the `required` and `type` values must be constants (i.e. either the schema is loaded from a file, or the
 * `as const` syntax is used for these)
 */
export type SchemaType<S extends Schema> = RequiredParameters<S> & NotRequiredParameters<S>;