Function cachedLookup

src/util.ts:82–93

(fn: (arg: T) => R)

 * Cached fs operation wrapper.
 */
export function cachedLookup<T, R>(fn: (arg: T) => R): (arg: T) => R {
  const cache = new Map<T, R>();

  return (arg: T): R => {
    if (!cache.has(arg)) {
      const v = fn(arg);
      cache.set(arg, v);
      return v;
    }
    return cache.get(arg)!;
  };
}

/**
 * @internal