Using embedded webview cancel button on iOS UI does not fire Error event on Xamarin.iOS

[terrencejames]

Xamarin.Auth Issue

Version

• [ ] nuget version = 1.6.0.2
• [ ] component version =

• [ ] sample

          Xamarin.Auth.OAuth2Authenticator authenticator = new Xamarin.Auth.OAuth2Authenticator(
              clientId: _clientId,
              scope: "",
              authorizeUrl: authorizeUri,
              redirectUrl: callbackUri)
          { ShowErrors = true };
  
          authenticator.AllowCancel = true;
          authenticator.Completed += Completed;
          authenticator.Error += Error;
  
          if (viewController is UINavigationController navController)
              viewController = navController.ViewControllers.Last();
          AppDelegate.AppWindow.BeginInvokeOnMainThread(() =>
          viewController.PresentViewController(authenticator.GetUI(), true, null));

Steps to reproduce

1. Run the above code so that the UI presents
2. Click the cancel button on the top left of the embedded webview (it's a little light but it's there)
3. Notice that error event is not fired, only completed event, so OnCancelled() is never called
4. Try to repeat step 1
5. Will not present the UI anymore probably because OnCancelled() was never called in the Completed Event

Platform: Tested on iPhone X

Expected behaviour

Error event is triggered so OnCancelled() can be called

Actual behaviour

Error event not triggered

Notes: Clicking the "Cancel" button below "Sign In" works as expected and the error event is raised

VS bug #733069

[terrencejames]

A temporary fix is disabling the AllowCancel flag, so that the user can just use the cancel button in the OAuth UI, but I expect there will not always be a cancel button

[moljac]

triaging it as "Low Priority"

In order to speed up the bugfixing, add link to the repo with minimal sample (with removed sensitve data)

[terrencejames]

Issue still happens, also notice that it happens on Android when clicking the hardware back button.

[terrencejames]

I've fixed the issue in the source code by calling authenticator.OnError(String.Empty); inside Cancel() in WebAuthenticatorController.cs