villa/src/awaitable.ts

Promise utilities for async/await-ready environment.

type AwaitableCreator<T> = (
  target: any,
  ...args: any[]
) => Promise<T> | undefined;

/** @internal */
export const awaitableCreators = [] as AwaitableCreator<any>[];

/**
 * Create a promise for an object.
 * @param emitter The emitter to listen on 'error' event for rejection, and
 *     given event types for fulfillment.
 * @param type A string or an array of string of event types for fulfillment.
 * @param errorEmitters Other emitters to listen on 'error' event for
 *     rejection.
 */
export function awaitable<T>(target: any, ...args: any[]): Promise<T> {
  for (let creator of awaitableCreators) {
    let promise = creator(target, ...args);

    if (promise) {
      return promise;
    }
  }

  throw new TypeError(
    'Cannot create awaitable from the target object with given arguments',
  );
}