Calling "url_for" in a Jinja2 template results in NoMatchFound

[EntangledLabs]

I am writing a web app in Starlette using Jinja2 templates. While writing a custom token auth system, I stumbled across a NoMatchFound error.

So, I tried to figure out why exactly it isn't working. In a lifespan manager, I printed out each route and its associated url_path_for like so:

@asynccontextmanager
async def lifespan(app):
    for route in app.router.routes:
        print(route)
        if isinstance(route, Mount):
            if isinstance(route.app, Router):
                for mount_route in route.app.routes:
                    print(mount_route)
                    print(mount_route.url_path_for(mount_route.name))
        else:
            print(route.url_path_for(route.name))

The following is the output:

Route(path='/', name='index', methods=['GET', 'HEAD'])
/
Route(path='/login', name='login', methods=['GET', 'HEAD'])
/login
Route(path='/logout', name='logout', methods=['GET', 'HEAD'])
/logout
Route(path='/token', name='get_token', methods=['POST'])
/token
Mount(path='/admin', name='', app=<starlette.routing.Router object at 0x000002CB2403E520>)
Mount(path='/user', name='', app=<starlette.routing.Router object at 0x000002CB24138640>)
Mount(path='/static', name='static', app=<starlette.staticfiles.StaticFiles object at 0x000002CB240396A0>)

So far, so good.

I then called url_path_for another time, except directly on the app's router object:

print(app.router.url_path_for('token'))

This is the resulting stack trace:

ERROR:    Traceback (most recent call last):
  File ".venv\Lib\site-packages\starlette\routing.py", line 693, in lifespan
    async with self.lifespan_context(app) as maybe_state:
               ~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "Python\Python313\Lib\contextlib.py", line 214, in __aenter__
    return await anext(self.gen)
           ^^^^^^^^^^^^^^^^^^^^^
  File "<project root>\main\webapp\main.py", line 30, in lifespan
    print(app.router.url_path_for('token'))
          ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File ".venv\Lib\site-packages\starlette\routing.py", line 662, in url_path_for
    raise NoMatchFound(name, path_params)
starlette.routing.NoMatchFound: No route exists for name "token" and params "".

As far as I can tell, I should be getting the appropriate path. Is there something I'm doing wrong here? Or is this an issue with Starlete?