Function loadChildren

packages/router/src/router_config_loader.ts:121–164

(
  route: Route,
  compiler: Compiler,
  parentInjector: Injector,
  onLoadEndListener?: (r: Route) => void,
)

 * an update to the extractor.
 */
export async function loadChildren(
  route: Route,
  compiler: Compiler,
  parentInjector: Injector,
  onLoadEndListener?: (r: Route) => void,
): Promise<LoadedRouterConfig> {
  const loaded = await wrapIntoPromise(
    runInInjectionContext(parentInjector, () => route.loadChildren!()),
  );
  const t = await maybeResolveResources(maybeUnwrapDefaultExport(loaded));

  let factoryOrRoutes: NgModuleFactory<any> | Routes;
  if (t instanceof NgModuleFactory || Array.isArray(t)) {
    factoryOrRoutes = t;
  } else {
    factoryOrRoutes = await compiler.compileModuleAsync(t);
  }

  if (onLoadEndListener) {
    onLoadEndListener(route);
  }
  // This injector comes from the `NgModuleRef` when lazy loading an `NgModule`. There is
  // no injector associated with lazy loading a `Route` array.
  let injector: EnvironmentInjector | undefined;
  let rawRoutes: Route[];
  let requireStandaloneComponents = false;
  let factory: NgModuleFactory<unknown> | undefined = undefined;
  if (Array.isArray(factoryOrRoutes)) {
    rawRoutes = factoryOrRoutes;
    requireStandaloneComponents = true;
  } else {
    injector = factoryOrRoutes.create(parentInjector).injector;
    factory = factoryOrRoutes;
    // When loading a module that doesn't provide `RouterModule.forChild()` preloader
    // will get stuck in an infinite loop. The child module's Injector will look to
    // its parent `Injector` when it doesn't find any ROUTES so it will return routes
    // for it's parent module instead.
    rawRoutes = injector.get(ROUTES, [], {optional: true, self: true}).flat();
  }
  const routes = rawRoutes.map(standardizeConfig);
  (typeof ngDevMode === 'undefined' || ngDevMode) &&
    validateConfig(routes, route.path, requireStandaloneComponents);
  return {routes, injector, factory};
}

async function maybeResolveResources<T>(value: T): Promise<T> {
  // In JIT mode we usually resolve the resources of components on bootstrap, however