Understanding routing and race conditions

[JovanVeljanoski]

Hello again,

Another.. tricky to explain question but I hope I will get the message across..

Say there is a button that does something like this

@solara.component
def SomePage():
   router = solara.use_router()
   solara.Button(label="logout", on_click=lambda: router.push("logout"))

The "logout" is another page (component) we can navigate to, that essentially does this

def logout(router):
    # do some logic
    # logic gives some URL that we need to redirect to (external possibly)
    router.push(logout_url)

@solara.component
def Logout():
    router = solara.use_router()
    # Some other solara visual components to be loaded.. like a progress bar or so
    solara.use_effect(lambda: logout(router), [])

In the above example, some kind of race condition happens, or whatever is called when the order of the routes/redirects/pushes is mixed up, and the process does not complete as it should. Which is strange to me as the use_effect should wait before everything is done/rendered before it executes the function right?

However, If I do something like this, everything works fine!
The example that works as expected:

def logout():
    # some logic that does stuff and generates an logout url
    return logout_url

@solara.component
def Logout():
    router = solara.use_router()
    # Some other solara visual components to be loaded.. like a progress bar or so

    def perform_logout():
        logout_url = logout()
        router.push(logout_url)
    solara.use_effect(perform_logout, [])

There is something fundamental I do not understand here.. may someone shed a bit of light here.. i hope the example is clear enough.. would be very challening to make a working example of this.
Many thanks!

[maartenbreddels]

I've stared at it for a few minutes, but I think this is totally equivalent code right?

[JovanVeljanoski]

Yes! :)
I thought so too.. but option one..i think essentially gets to some race conditions and one rerouting is interrupted by another.
In option 2 it does not happen somehow.. i wanted to understand it.. and know if I am doing anything wrong..

Perhaps something with the rendering etc.. but i thought use_effect takes care of that (waits until the render is complete). But maybe with routing is different?

[maartenbreddels]

What I mean is that the code is fully equivalent, and does not behave different.

Maybe you can have a better reproducing example that shows the issue, then I can take another look.