Fix issue with redirects in server fns creating multiple Location headers

[benwis]

Because headers from ResponseOptions were set before the default referral on form submission, you could use redirect() in your server fn, and the default referral would add another Location header, if it was a form submission. Then everything would blow up.

[fundon]

On the server side, we can use is_success or is_redirection to check the status.

[benwis]

Or use is_success and is_redirection.

I did not know those existed! But I don't think a number of 3xx error codes are valid responses for our Form component

[benwis]

@gbj You'll probably want to take a look at this. I believe I've fixed the behavior in a quite kludgy way.
Because gloo_net follows redirects, we'll never get a 3xx response. It'll always be either a 200 or a 4xx with a redirected=true value on it. I tried disabling that, but then it returns status code 0 and no headers, which is even less helpful.

I've changed it to check for that, and redirect based on the url() field in the 200 response. But to do that I had to import the url crate(which looked like it was disabled for hydration), to convert the absolute path into a relative one for navigate()

Also, navigating this way produces a warning and a panic in the leptos reactive code in the firefox console, something about updating non-existent signals.

But hey, it redirects, so......

[gbj]

@gbj You'll probably want to take a look at this. I believe I've fixed the behavior in a quite kludgy way. Because gloo_net follows redirects, we'll never get a 3xx response. It'll always be either a 200 or a 4xx with a redirected=true value on it. I tried disabling that, but then it returns status code 0 and no headers, which is even less helpful.

Ah okay, great! Good work figuring this out.

By the way you seem to have committed some Nix-related files inadvertently (.direnv, .envrc, flake.nix)

I've changed it to check for that, and redirect based on the url() field in the 200 response. But to do that I had to import the url crate(which looked like it was disabled for hydration), to convert the absolute path into a relative one for navigate()

There's already a Url implementation in the router that uses the browser's native URL parsing on the client or the url crate on the server, so I've changed this just to use that and avoid the import in Wasm.

Also, navigating this way produces a warning and a panic in the leptos reactive code in the firefox console, something about updating non-existent signals.

But hey, it redirects, so......
Believe it or not this is because it's using a server action and deserializing the JSON from the response is asynchronous, so it was actually trying to update the values in the action after navigating away from the page. I've fixed the panics; the warnings will still show but I don't think that's really an issue.