Method doRequest

packages/common/http/src/fetch.ts:133–335

(
    request: HttpRequest<any>,
    signal: AbortSignal,
    observer: Observer<HttpEvent<any>>,
  )

  }

  private async doRequest(
    request: HttpRequest<any>,
    signal: AbortSignal,
    observer: Observer<HttpEvent<any>>,
  ): Promise<void> {
    const init = this.createRequestInit(request);
    let response;
    try {
      // Run fetch outside of Angular zone.
      // This is due to Node.js fetch implementation (Undici) which uses a number of setTimeouts to check if
      // the response should eventually timeout which causes extra CD cycles every 500ms
      const fetchPromise = this.ngZone.runOutsideAngular(() =>
        this.fetchImpl(request.urlWithParams, {signal, ...init}),
      );

      // Make sure Zone.js doesn't trigger false-positive unhandled promise
      // error in case the Promise is rejected synchronously. See function
      // description for additional information.
      silenceSuperfluousUnhandledPromiseRejection(fetchPromise);

      // Send the `Sent` event before awaiting the response.
      observer.next({type: HttpEventType.Sent});

      response = await fetchPromise;
    } catch (error: any) {
      observer.error(
        new HttpErrorResponse({
          error,
          status: error.status ?? 0,
          statusText: error.statusText,
          url: request.urlWithParams,
          headers: error.headers,
        }),
      );
      return;
    }

    const headers = new HttpHeaders(response.headers);
    const statusText = response.statusText;
    const url = response.url || request.urlWithParams;

    let status = response.status;
    let body: string | ArrayBuffer | Blob | object | null = null;

    const reportDownloadProgress = request.reportProgress || request.reportDownloadProgress;
    if (reportDownloadProgress) {
      observer.next(new HttpHeaderResponse({headers, status, statusText, url}));
    }

    if (response.body) {
      const contentType = response.headers.get(CONTENT_TYPE_HEADER) ?? '';

      // Read Progress
      const contentLength = response.headers.get('content-length');
      const contentLengthValue = contentLength !== null ? Number(contentLength) : NaN;

      if (
        this.maxResponseSize !== null &&