Function once

lib/events.js:990–1032

* Creates a `Promise` that is fulfilled when the emitter * emits the given event. * @param {EventEmitter} emitter * @param {string | symbol} name * @param {{ signal: AbortSignal; }} [options] * @returns {Promise}

(emitter, name, options = kEmptyObject)

 * @returns {Promise}
 */
async function once(emitter, name, options = kEmptyObject) {
  validateObject(options, 'options');
  const { signal } = options;
  validateAbortSignal(signal, 'options.signal');
  if (signal?.aborted)
    throw new AbortError(undefined, { cause: signal.reason });
  return new Promise((resolve, reject) => {
    const errorListener = (err) => {
      emitter.removeListener(name, resolver);
      if (signal != null) {
        eventTargetAgnosticRemoveListener(signal, 'abort', abortListener);
      }
      reject(err);
    };
    const resolver = (...args) => {
      if (typeof emitter.removeListener === 'function') {
        emitter.removeListener('error', errorListener);
      }
      if (signal != null) {
        eventTargetAgnosticRemoveListener(signal, 'abort', abortListener);
      }
      resolve(args);
    };

    kResistStopPropagation ??= require('internal/event_target').kResistStopPropagation;
    const opts = { __proto__: null, once: true, [kResistStopPropagation]: true };
    eventTargetAgnosticAddListener(emitter, name, resolver, opts);
    if (name !== 'error' && typeof emitter.once === 'function') {
      // EventTarget does not have `error` event semantics like Node
      // EventEmitters, we listen to `error` events only on EventEmitters.
      emitter.once('error', errorListener);
    }
    function abortListener() {
      eventTargetAgnosticRemoveListener(emitter, name, resolver);
      eventTargetAgnosticRemoveListener(emitter, 'error', errorListener);
      reject(new AbortError(undefined, { cause: signal?.reason }));
    }
    if (signal != null) {
      eventTargetAgnosticAddListener(
        signal, 'abort', abortListener, { __proto__: null, once: true, [kResistStopPropagation]: true });
    }
  });
}

function createIterResult(value, done) {
  return { done, value };