Modify browser location from server

[mwx23]

This is a feature request.

My use-case is that I have a menu to select items from a route /items/<item_id>.

I can of course do with <a href='/items/123' />. This however results in a page reload.

I am currently using <button/>s with a server-side function that just replaces item in the DOM, mostly because I can with lona :)

The only issue with that is it would be nice if the server-side could update the location in the browser if the user wishes to bookmark that page.

Basically the ability to send data to the browser history.replaceState() API.

[mwx23]

Sorry I just realised this should be over in the Feature Request section of Discussions.

[fscherf]

No worries, converted it :)

[fscherf]

Hm i am not sure if i want such a feature. Let's say there was LonaView.set_url(). Should you able to set the URL to / if the "real" URL is /foo/? Should you be able to extend the URL within the current URL as a prefix like /foo/ to /foo/bar/? Also what should happen it the server has a route for /foo/bar/? What should happen if the back button or the refresh button is clicked?

It adds a whole new dimension to debugging as well. If a user states "i have a problem with the view behind /foo/bar/" you can't just look in the routing table to find the broken view.

Seems like a lot added complexity to save a few redirects. Also in my experience it's a bad idea to tinker with the browser history for the most part. It gets confusing very fast, therefore i tried to emulate the behavior a siple flask app would have (and I needed 3 attempts to get that right)

If you really want that you ca, add that as a custom feature to your frontend template. I can give you a code example if you want

[maratori]

What about following use case?
There is a page /stock/<ticker> to show some info about stocks.
This page also contains a drop down to select different ticker.
Is it possible to do redirection inside Select.handle_change()?
What is the most Lona-way to implement that?

[fscherf]

@maratori I am sorry, that's currently not possible. Only LonaView.handle_request() and Middleware.handle_request() can send redirects, because redirects are implemented as responses.

But maybe that's a good idea

[fscherf]

@maratori I actually have a use case for redirects from handle_change() or handle_click() myself. Should we open a feature-request for this?

[maratori]

@fscherf Yes, why not?

[fscherf]

@maratori it's actually not that hard to implement. I created #159 (it's not the nicest code, and i have to write documentation for the release, but for now it's ok i guess)

[fscherf]

@mwx23 I changed the label to Q&A, because it's not a feature request anymore :)

[mwx23]

Just an update on my implementation for those interested.

Also this solution means you should be able to run other DOM methods (completely untested, buyer beware...).
Obviously more care needs to be taken with the deserialisation from python. Perhaps a more formalised JSON structure.

// frontend.js
    lona_context.add_message_handler(function (lona_context, raw_message) {
        if (!raw_message.startsWith('custom-message:')) {
            return raw_message;
        }
        let [namespace, method, ...args] = raw_message.split(':');
        let cmd = `${method}(...args)`;
        let res = eval(cmd);
        // serialise res and send it back to the server 
        // lona_context.send(`custom-message:${serialisedRes}`);
    });

Then in my View:

self.send_str(f'custom-message:window.history.replaceState::my new tab title:/my/updated/route')

Absolutely loving how easy lona is to extend!

[fscherf]

@mwx23 Looks good! I do something similar in some of my work related projects to implement desktop notifications.
I am very glad Lona seems not to be in your way when you try to solve problems :)