Not Found in beforeLoad and Loader does not behave as expected

[ViewableGravy]

Describe the bug

As described in the steps below, It looks like the notFound error that can be thrown from beforeLoad or the loader is not properly causing the right route to render their notFound component.

If notFound is thrown in beforeLoad, the root route will ALWAYS be the one to render the not found component. Based on router dev tools (which I have inserted above the root route so they do not unmount in my example), it looks like this is because throwing a not found error in beforeLoad causes all parent routes to also become notFound and therefore the root handles it, meaning that no layout is rendered.

If notFound is thrown in a loader, assuming that the loader ran as a result of a navigation or preload, then the notFound behaviour works as expected. However, if the loader is running on the first render of the router, this error propagates to the root route and causes the entire page to show the not found component. Interestingly, in this case, the about route doesn't actually get marked as notFound in the router state, but for some reason the root route still handles the notFound instead of the about component.

Your Example Website or App

https://stackblitz.com/edit/tanstack-router-cxbsxj?file=src%2Froutes%2F__root.tsx

Steps to Reproduce the Bug or Issue

1. Load app to index route and navigate to before-load-not-found route. The root route will handle the not found instead of about, despite about being a parent and rendering an Outlet ❌
2. Load app to index route and navigate to loader-not-found route. The about route renders it's layout and a not found in the outlet position ✅
3. Load the app to the loader-not-found route (navigate to that page and then refresh the page). The root route handles the not found ❌

Expected behavior

1. Load app to index route and navigate to before-load-not-found route. The about route should render it's layout and in the outlet position, the default notFound component
2. Load app to index route and navigate to loader-not-found route. The about route renders it's layout and a not found in the outlet position
3. Load the app to the loader-not-found route (navigate to that page and then refresh the page). The about route should render it's layout and in the outlet poisition, the default notFound component

Screenshots or Videos

No response

Platform

• OS: [Windows]
• Browser: [Arc]
• Version: [Tanstack/router: 1.48.1]

Additional context

I noticed this because during my implementation of the router, I've created a middleware function (to run in beforeLoad) to check if a route is enabled for the website our application is running as. Previously this used redirects and as far as I can tell, redirects work completely fine, but may just be luck, because with a redirect, it's not really staying on the same route, so even if the same incorrect matching was to propagate up the routes, it wouldn't really matter since it's going to be redirected anyway.

In my example, I moved the Tanstack Dev tools into the InnerWrap so that they stay mounted on a not-found, helps a little.

I've also tested the following cases which behave the same:

1. defaultNotFoundComponent manually set (createRouter & RouterProvider)
2. Explicit not found component on about route
3. No component set on about route

[ViewableGravy]

Hey, just wondering if there is any update on whether this is something that is getting looked into or aware of.

This bug causes the use of notFound() in beforeLoad and loader to be unreliable and effectively unusable in the context they are designed for.

If there is any other information that I can provide, let me know.

[nstepien]

If notFound is thrown in beforeLoad, the root route will ALWAYS be the one to render the not found component.

From my experience it's even worse: the RootComponent is not rendered at all.
This leads to context providers from the RootComponent not being rendered, which then break our NotFound component, as the IntlProvider context is not available for localization.

https://stackblitz.com/edit/github-fcvgqy?file=src%2FContext.ts,src%2Froutes%2F__root.tsx,src%2Fmain.tsx,src%2Froutes%2Fabout.tsx

Additional context:
Throwing any other error in beforeLoad works fine, the default error component correctly renders at the closest Outlet.

[Mario-Eis]

This issue hits us hard at the moment. In our use case we want to render "not found" for routes, the current user hast no permission for. So, according to the documentation, we do the authentication and authorization checks in beforeLoad. But throwing a notFount() there, just breaks the application. Because in our case, when rendering the root route, authentication is not done yet (we use different authentication mechanisms for different routes and inject them with router.update to the router context further down the component tree).
And also the design system is not initialized in the root route either (also further down). So the whole thing falls back to the ugly root level 404 page too. Instead of keeping the current layout form the layout routes.

[nikuscs]

Same, trying to use a catch all on the root and throwing a notFound on the beforeLoad will indeed print out a 404 component without anything from the __root.tsx

[Etsija]

We are seeing exactly the same problem in our app: if notFound() is thrown inside beforeLoad, our specified notFoundComponent will never be rendered. This has worked for us before, but I have no information about the router version where it stopped working.

[longzheng]

I can confirm this beforeLoad issue still affects v1.99.3. (Throwing notFound in loader seems to work correctly)

I'm using a workaround using a custom error class inside beforeLoad instead of notFound().

export class NotFoundError extends Error {
  constructor(message?: string) {
    super(message);
    this.name = 'NotFoundError';
    Object.setPrototypeOf(this, NotFoundError.prototype);
  }
}

export const Route = createFileRoute('/about/before-load-not-found')({
  beforeLoad() {
    throw new NotFoundError();
  },
  component: () => <div>Hello /about/not-found!</div>,
  errorComponent: ({ error }) => {
    if (error instanceof NotFoundError) {
      return <>Not Found</>;
    }

    throw error;
  },
});

Demo https://stackblitz.com/edit/tanstack-router-nutwasgj?file=src%2Froutes%2Fabout.before-load-not-found.tsx