Method withCache

packages/cache/src/service.ts:256–273

* Cache wrapper for functions (cache-aside). * * Bare JSON null is treated as a miss; use withCacheNullable for intentional null values. * Never throws due to cache errors; function errors propagate without retry. * * @param fn - Function to execute (and optionally cache). * @param

(
    fn: () => Promise<T>,
    key: CacheKey,
    ttlMs: number
  )

   * @returns Cached value if present, otherwise fresh result from fn()
   */
  async withCache<T extends NonNullable<unknown>>(
    fn: () => Promise<T>,
    key: CacheKey,
    ttlMs: number
  ): Promise<T> {
    if (!this.canUseCache(key, ttlMs)) {
      return await fn();
    }

    const cachedValue = await this.tryGetCachedValue<T>(key, ttlMs);
    if (cachedValue !== undefined) {
      return cachedValue;
    }

    const fresh = await fn();
    await this.trySetCache(key, fresh, ttlMs);
    return fresh;
  }

  /**
   * Cache wrapper for functions whose result may legitimately be `null`.