Detect cross-origin redirects during visits

[svara]

This PR is the counterpart of the Android hotwired/hotwire-native-android#82.
Due to CORS restrictions, the javascript Fetch API cannot be reliably used across applications to detect cross-origin redirects during Turbo visits.

This new approach hands off failed visits with a non-HTTP status code (which suggests a cross-origin redirect may have been attempted) to the native code to detect cross-origin redirects. If a visit redirect is detected, the final redirect location is treated as an external URL and opened appropriately.

[jayohms]

Looks great, nice work on this @svara.

[joemasilotti]

Using Demo PR #12, I'm seeing the external redirect open in SFSafariViewController. What do I need to configure to test this fully? I'm not seeing how I can implement handle(externalURL:) for this to work.

[ibrahima]

Hi! This is helpful, I've noticed this issue before as well, so thanks for resolving it!

I was wondering, is there a way to handle this differently from within my application code? E.g., if I wanted to open this in a webview within my app, would there be a way to set that up? (At this point I don't know for sure if this would help me, but it's something I'm considering to handle a specific situation with my app.)

Edit: Never mind, I don't have the same need anymore. But I'm just curious if there's something one can do here, because when I print out visit proposals in my NavigatorDelegate it doesn't show anything for the cross-origin redirects. (But maybe that's true of all redirects, actually...)

[jayohms]

@ibrahima while it's not currently possible, we're going to begin some work soon in the iOS library to make navigation more customizable through the same RouteDecisionHandler concept that Android uses. I don't have a specific timeline, but we're going to align this aspect between platforms so iOS is more flexible and the platforms are consistent: https://native.hotwired.dev/android/reference#handling-url-routes