Method from

packages/angular/ssr/src/routes/router.ts:48–73

* Creates or retrieves a `ServerRouter` instance based on the provided manifest and URL. * * If the manifest contains pre-built routes, a new `ServerRouter` is immediately created. * Otherwise, it builds the router by extracting routes from the Angular configuration * asynchronously. Thi

(manifest: AngularAppManifest, url: URL)

   * @returns A promise resolving to a `ServerRouter` instance.
   */
  static from(manifest: AngularAppManifest, url: URL): Promise<ServerRouter> {
    if (manifest.routes) {
      const routeTree = RouteTree.fromObject(manifest.routes);

      return Promise.resolve(new ServerRouter(routeTree));
    }

    // Create and store a new promise for the build process.
    // This prevents concurrent builds by re-using the same promise.
    ServerRouter.#extractionPromise ??= extractRoutesAndCreateRouteTree({ url, manifest })
      .then(({ routeTree, errors }) => {
        if (errors.length > 0) {
          throw new Error(
            'Error(s) occurred while extracting routes:\n' +
              errors.map((error) => `- ${error}`).join('\n'),
          );
        }

        return new ServerRouter(routeTree);
      })
      .finally(() => {
        ServerRouter.#extractionPromise = undefined;
      });

    return ServerRouter.#extractionPromise;
  }

  /**
   * Matches a request URL against the route tree to retrieve route metadata.