Function resolveMap

packages/context/src/value-promise.ts:95–129

(
  map: MapObject<T>,
  resolver: (val: T, key: string, values: MapObject<T>) => ValueOrPromise<V>,
)

 * be invoked with the property value, the property name, and the source object.
 */
export function resolveMap<T, V>(
  map: MapObject<T>,
  resolver: (val: T, key: string, values: MapObject<T>) => ValueOrPromise<V>,
): ValueOrPromise<MapObject<V>> {
  const result: MapObject<V> = {};
  let asyncResolvers: PromiseLike<void>[] | undefined = undefined;

  const setter = (key: string) => (val: V) => {
    if (val !== undefined) {
      // Only set the value if it's not undefined so that the default value
      // for a key will be honored
      result[key] = val;
    }
  };

  for (const key in map) {
    const valueOrPromise = resolver(map[key], key, map);
    if (isPromiseLike(valueOrPromise)) {
      if (!asyncResolvers) asyncResolvers = [];
      asyncResolvers.push(valueOrPromise.then(setter(key)));
    } else {
      if (valueOrPromise !== undefined) {
        // Only set the value if it's not undefined so that the default value
        // for a key will be honored
        result[key] = valueOrPromise;
      }
    }
  }

  if (asyncResolvers) {
    return Promise.all(asyncResolvers).then(() => result);
  } else {
    return result;
  }
}

/**
 * Resolve entries of an array into a new array with the same indexes. If one or