Function resolveDerivedComponent

http/unstable_message_signatures.ts:413–434

(
  name: string,
  message: Request | Response,
  params: ComponentParameters,
  parsedUrl: { value?: URL },
)

]);

function resolveDerivedComponent(
  name: string,
  message: Request | Response,
  params: ComponentParameters,
  parsedUrl: { value?: URL },
): string {
  if (REQUEST_ONLY_DERIVED.has(name)) {
    if (!(message instanceof Request)) {
      throw new TypeError(`Cannot use "${name}" on a response message`);
    }
    return resolveRequestDerived(name, message, params, parsedUrl);
  }

  if (name === "@status") {
    if (message instanceof Request) {
      throw new TypeError(`Cannot use "${name}" on a request message`);
    }
    return String(message.status);
  }

  throw new TypeError(`Unknown derived component "${name}"`);
}

function resolveRequestDerived(
  name: string,