Delegate callback when web view process terminates

[joemasilotti]

This is an intermediary solution for #50.

In summary, WKWebView can terminate under certain circumstances when in the background. When a Turbo-powered app is re-opened after this occurs the app can be left in a weird state.

This PR adds a new delegate callback, sessionWebViewProcessDidTerminate(_:), that developers can hook into to do what they see fit. @tony42, for example, is resetting the state of their app. I'm following that same approach.

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I'm not sure if/how this can be handled better inside of this library short of iOS 16 fixing the issue entirely. So this feels like the next best approach as it puts the power back in the developer's hands.

[tony42]

@joemasilotti thanks for implementing the hook.

[ghiculescu]

@joemasilotti @tony42 do either of you have any tips on how to fix this without this PR being merged? I'm not a Swift expert, is there an equivalent to Ruby monkey patching to implement the fix right away?

[joemasilotti]

Not that I'm aware of, no. You could try to become the web view delegate, but that might mess things up with how the framework listens for events.

@jayohms will need to merge this in to enable the hook.

[chriskroon]

Hey, when I try to use this commit to my package, I get a build error:
Type 'SceneDelegate' does not conform to protocol 'SessionDelegate'

Am I doing something wrong?

Cheers,
Chris

[joemasilotti]

@chriskroon, nope! You need to implement the new method in SceneDelegate.

extension SceneDelegate: SessionDelegate { // If you already have this defined then only add the implementation below.
    func sessionWebViewProcessDidTerminate(_ session: Session) {
        // ...
    }
}

[chriskroon]

Hey Joe,

I found that out by myself and I thought that I replied haha.
Thx Joe!

Cheers,
Chris

[jayohms]

Thanks for exposing this hook and sorry for the delay!

[dginsburg]

Thanks for diagnosing and fixing this @joemasilotti. I'd been tearing my hair out trying to figure out why the first visit was failing after the app had been in the background for a long time. I had assumed the app was terminated and the failure was part of a turbo cold boot.

[ghiculescu]

For those watching this issue, has anyone implemented anything apart from this callback?

https://nevermeant.dev/handling-blank-wkwebviews/ and Telerik-Verified-Plugins/WKWebView#248 (comment) discuss timer-based approaches and I am curious if anyone has used them in a Turbo context with success. (Or if they haven't needed to because just implementing this callback and calling session.reload() did the job.)

[joemasilotti]

In the Turbo Native apps I build and maintain I reset the entire app in the callback. For example, usually something like this.

func sessionWebViewProcessDidTerminate(_ session: Session) {
    navigationController.popViewController(animated: false)
    navigationController.viewControllers = []

    self.session = createSession()
    modalSession = createSession()

    startApp()
}

[ghiculescu]

Nice, I might try the same. Have you found a reliable way to replicate the issue so you can test it?

[joemasilotti]

Usually by opening our app then opening a bunch of other apps and switching back to ours. Playing a graphically intense game for a few seconds usually triggers it.

[joemasilotti]

Following up for anyone who lands here in the future.

My comment above doesn't seem to work 100% of the time. Instead, I've opted for restarting the entire app as if it was launched cold. It's a worse experience for the user, but it works 100% of the time which is a better trade-off for me.

[chriskroon]

Hey Joe,

I also implemented it that way, this hook you can use for whenever a scene will become active again

 func sceneWillEnterForeground(_ scene: UIScene) {
       // Your Code 
       (I open a link whenever it's set by a push notification of the last link)
    }