Function callValidatedThen

packages/capnweb-validate/src/internal/core.ts:1122–1151

(
  target: (...args: unknown[]) => unknown,
  receiver: unknown,
  returns: Validator,
  path: PropertyPath,
  side: WrapSide,
  mode: ValidationMode,
  onfulfilled?: ((value: unknown) => unknown) | null,
  onrejected?: ((reason: unknown) => unknown) | null
)

}

function callValidatedThen(
  target: (...args: unknown[]) => unknown,
  receiver: unknown,
  returns: Validator,
  path: PropertyPath,
  side: WrapSide,
  mode: ValidationMode,
  onfulfilled?: ((value: unknown) => unknown) | null,
  onrejected?: ((reason: unknown) => unknown) | null
): Promise<unknown> {
  let then = Reflect.get(target, "then", receiver) as (
    onfulfilled?: ((value: unknown) => unknown) | null,
    onrejected?: ((reason: unknown) => unknown) | null
  ) => Promise<unknown>;
  return Reflect.apply(then, target, [
    (value: unknown) => {
      // Validation runs in the fulfillment handler; route a failure to onrejected so the awaiter rejects rather than hangs,
      // or rethrow when there is no onrejected (bare `.then(onF)`) to reject the chained promise.
      let wrapped: unknown;
      try {
        wrapped = validateResolvedValue(value, returns, path, side, mode);
      } catch (err) {
        if (onrejected) return onrejected(err);
        throw err;
      }
      return onfulfilled ? onfulfilled(wrapped) : wrapped;
    },
    onrejected,
  ]);
}

function methodSpecFor(
  validator: Validator,