WPF XAML designer broken when using RoutedViewHost

[glennawatson]

Do you want to request a feature or report a bug?
bug

What is the current behavior?
RoutedViewHost when in WPF design mode will have a error complaining about the lack of IActivationForViewFetcher

This is due to ModeDetector.InUnitTestRunner() is not detecting the design mode correctly.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem

1. Check out https://github.com/ApexAutomation/BaseApp
2. Load the MainWindow in either the xaml designer or the blend designer inside visual studio.

What is the expected behavior?
That you can design using the xaml editor.

What is the motivation / use case for changing the behavior?
Fix previously working experiences for users. Fix user experience first found in https://stackoverflow.com/questions/51525704/using-reactiveui-v8-routedviewhost-in-wpf

Which versions of ReactiveUI, and which platform / OS are affected by this issue? Did this work in previous versions of ReativeUI? Please also test with the latest stable and development snapshot
RxUI 8.3.1 WPF

[ghuntley]

👍

[Asesjix]

I do not think it's up to Mode.Detector.IsUnitTestRunner().
Because the Designer works with the current ReativeUI master.
I think the cause was the same issue as Issue #1016 which I fixed with PR #1651.
@glennawatson Can you verify that?

[glennawatson]

This appears to be fixed with 8.4.1. Thanks