Function retrieveStateFromCache

packages/common/http/src/transfer_cache.ts:199–276

(
  req: HttpRequest<unknown>,
  options: CacheOptions,
  transferState: TransferState,
  originMap: Record<string, string> | null,
  storeKey?: StateKey<TransferHttpResponse>,
  skipUseCacheChecks = false,
)

 * @param skipUseCacheChecks Whether to skip the use cache checks. (Only disable when the checks have been performed beforehand).
 */
export function retrieveStateFromCache(
  req: HttpRequest<unknown>,
  options: CacheOptions,
  transferState: TransferState,
  originMap: Record<string, string> | null,
  storeKey?: StateKey<TransferHttpResponse>,
  skipUseCacheChecks = false,
): HttpResponse<unknown> | null {
  if (!skipUseCacheChecks && !canUseOrCacheRequest(req, options)) {
    return null;
  }

  if (typeof ngServerMode !== 'undefined' && !ngServerMode && originMap) {
    throw new RuntimeError(
      RuntimeErrorCode.HTTP_ORIGIN_MAP_USED_IN_CLIENT,
      ngDevMode &&
        'Angular detected that the `HTTP_TRANSFER_CACHE_ORIGIN_MAP` token is configured and ' +
          'present in the client side code. Please ensure that this token is only provided in the ' +
          'server code of the application.',
    );
  }

  if (!storeKey) {
    const requestUrl =
      typeof ngServerMode !== 'undefined' && ngServerMode && originMap
        ? mapRequestOriginUrl(req.url, originMap)
        : req.url;

    storeKey = makeCacheKey(req, requestUrl);
  }

  const response = transferState.get(storeKey, null);

  if (!response) {
    return null;
  }

  const {
    [BODY]: undecodedBody,
    [RESPONSE_TYPE]: responseType,
    [HEADERS]: httpHeaders,
    [STATUS]: status,
    [STATUS_TEXT]: statusText,
    [REQ_URL]: url,
  } = response;
  // Request found in cache. Respond using it.
  let body: ArrayBuffer | Blob | string | undefined = undecodedBody;

  switch (responseType) {
    case 'arraybuffer':
      body = fromBase64(undecodedBody);
      break;
    case 'blob':
      body = new Blob([fromBase64(undecodedBody)]);
      break;
  }

  // We want to warn users accessing a header provided from the cache