Method handleCache

packages/client/lib/client/cache.ts:543–617

(
    client: CachingClient,
    parser: BasicCommandParser,
    fn: CmdFunc,
    transformReply?: TransformReply,
    typeMapping?: TypeMapping
  )

  4. return previously non cached result
  */
  override async handleCache(
    client: CachingClient,
    parser: BasicCommandParser,
    fn: CmdFunc,
    transformReply?: TransformReply,
    typeMapping?: TypeMapping
  ) {
    let reply: ReplyUnion;

    const cacheKey = generateCacheKey(parser.redisArgs);

    // "2"
    let cacheEntry = this.get(cacheKey);

    if (cacheEntry) {
      // If instanceof is "too slow", can add a "type" and then use an "as" cast to call proper getters.
      if (cacheEntry instanceof ClientSideCacheEntryValue) { // "2b1"
        this.#statsCounter.recordHits(1);
        publish(CHANNELS.CACHE_REQUEST, () => ({ result: 'hit', clientId: client._clientId }));

        return structuredClone(cacheEntry.value);
      } else if (cacheEntry instanceof ClientSideCacheEntryPromise) { // 2b2
        // This counts as a miss since the value hasn't been fully loaded yet.
        this.#statsCounter.recordMisses(1);
        publish(CHANNELS.CACHE_REQUEST, () => ({ result: 'miss', clientId: client._clientId }));
        reply = await cacheEntry.promise;
      } else {
        throw new Error("unknown cache entry type");
      }
    } else { // 3/3a
      this.#statsCounter.recordMisses(1);
      publish(CHANNELS.CACHE_REQUEST, () => ({ result: 'miss', clientId: client._clientId }));

      const startTime = performance.now();
      const promise = fn();

      cacheEntry = this.createPromiseEntry(client, promise);
      this.set(cacheKey, cacheEntry, parser.keys);

      try {
        reply = await promise;
        const loadTime = performance.now() - startTime;
        this.#statsCounter.recordLoadSuccess(loadTime);
      } catch (err) {
        const loadTime = performance.now() - startTime;
        this.#statsCounter.recordLoadFailure(loadTime);

        if (cacheEntry.validate()) {
          this.delete(cacheKey!);
        }

        throw err;
      }
    }

    // 3b
    let val;
    if (transformReply) {