Show DefaultContent when Router is set to null

src/Avalonia.ReactiveUI/RoutedViewHost.cs

@@ -65,9 +65,15 @@ namespace Avalonia.ReactiveUI
         {
             this.WhenActivated(disposables =>
             {
-                this.WhenAnyObservable(x => x.Router.CurrentViewModel)
-                    .StartWith(default(object))
-                    .DistinctUntilChanged()
+                var routerRemoved = this
+                    .WhenAnyValue(x => x.Router)
+                    .Where(router => router == null)
+                    .Cast<object>();
+
+                this.WhenAnyValue(x => x.Router)
+                    .Where(router => router != null)
+                    .SelectMany(router => router.CurrentViewModel)
+                    .Merge(routerRemoved)
                     .Subscribe(NavigateToViewModel)
                     .DisposeWith(disposables);
             });

tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs

@@ -61,15 +61,7 @@ namespace Avalonia.ReactiveUI.UnitTests
         }
 
         [Fact]
-        public void Should_Not_Override_Data_Template_Binding_When_Item_Template_Is_Set()
-        {
-            var view = new ExampleView(control => control.ItemTemplate = GetItemTemplate());
-            Assert.NotNull(view.List.ItemTemplate);
-            Assert.IsType<FuncDataTemplate<TextBlock>>(view.List.ItemTemplate);
-        }
-
-        [Fact]
-        public void Should_Use_View_Model_View_Host_As_Data_Template()
+        public void Should_Use_ViewModelViewHost_As_Data_Template_By_Default()
         {
             var view = new ExampleView();
             view.ViewModel.Items.Add(new NestedViewModel());
@@ -82,22 +74,36 @@ namespace Avalonia.ReactiveUI.UnitTests
         }
 
         [Fact]
-        public void Should_Not_Use_View_Model_View_Host_When_Item_Template_Is_Set()
+        public void ViewModelViewHost_Should_Resolve_And_Embedd_Appropriate_View_Model()
         {
-            var view = new ExampleView(control => control.ItemTemplate = GetItemTemplate());
+            var view = new ExampleView();
             view.ViewModel.Items.Add(new NestedViewModel());
 
             var child = view.List.Presenter.Panel.Children[0];
             var container = (ContentPresenter) child;
             container.UpdateChild();
 
-            Assert.IsType<TextBlock>(container.Child);
+            var host = (ViewModelViewHost) container.Child;
+            Assert.IsType<NestedViewModel>(host.ViewModel);
+            Assert.IsType<NestedViewModel>(host.DataContext);
+
+            host.DataContext = "changed context";
+            Assert.IsType<string>(host.ViewModel);
+            Assert.IsType<string>(host.DataContext);
         }
-        
+
         [Fact]
-        public void Should_Not_Use_View_Model_View_Host_When_Data_Templates_Are_Not_Empty()
+        public void Should_Not_Override_Data_Template_Binding_When_Item_Template_Is_Set()
         {
-            var view = new ExampleView(control => control.DataTemplates.Add(GetItemTemplate()));
+            var view = new ExampleView(control => control.ItemTemplate = GetItemTemplate());
+            Assert.NotNull(view.List.ItemTemplate);
+            Assert.IsType<FuncDataTemplate<TextBlock>>(view.List.ItemTemplate);
+        }
+
+        [Fact]
+        public void Should_Not_Use_View_Model_View_Host_When_Item_Template_Is_Set()
+        {
+            var view = new ExampleView(control => control.ItemTemplate = GetItemTemplate());
             view.ViewModel.Items.Add(new NestedViewModel());
 
             var child = view.List.Presenter.Panel.Children[0];
@@ -106,24 +112,18 @@ namespace Avalonia.ReactiveUI.UnitTests
 
             Assert.IsType<TextBlock>(container.Child);
         }
-
+        
         [Fact]
-        public void Should_Resolve_And_Embedd_Appropriate_View_Model()
+        public void Should_Not_Use_View_Model_View_Host_When_Data_Templates_Are_Not_Empty()
         {
-            var view = new ExampleView();
+            var view = new ExampleView(control => control.DataTemplates.Add(GetItemTemplate()));
             view.ViewModel.Items.Add(new NestedViewModel());
 
             var child = view.List.Presenter.Panel.Children[0];
             var container = (ContentPresenter) child;
             container.UpdateChild();
 
-            var host = (ViewModelViewHost) container.Child;
-            Assert.IsType<NestedViewModel>(host.ViewModel);
-            Assert.IsType<NestedViewModel>(host.DataContext);
-
-            host.DataContext = "changed context";
-            Assert.IsType<string>(host.ViewModel);
-            Assert.IsType<string>(host.DataContext);
+            Assert.IsType<TextBlock>(container.Child);
         }
 
         private static FuncDataTemplate GetItemTemplate()

tests/Avalonia.ReactiveUI.UnitTests/RoutedViewHostTest.cs

@@ -62,50 +62,42 @@ namespace Avalonia.ReactiveUI.UnitTests
                 PageTransition = null
             };
 
-            var root = new TestRoot 
-            { 
-                Child = host 
+            var root = new TestRoot
+            {
+                Child = host
             };
             
             Assert.NotNull(host.Content);
-            Assert.Equal(typeof(TextBlock), host.Content.GetType());
+            Assert.IsType<TextBlock>(host.Content);
             Assert.Equal(defaultContent, host.Content);
 
             var first = new FirstRoutableViewModel();
-            screen.Router.Navigate
-                .Execute(first)
-                .Subscribe();
+            screen.Router.Navigate.Execute(first).Subscribe();
 
             Assert.NotNull(host.Content);
-            Assert.Equal(typeof(FirstRoutableView), host.Content.GetType());
+            Assert.IsType<FirstRoutableView>(host.Content);
             Assert.Equal(first, ((FirstRoutableView)host.Content).DataContext);
             Assert.Equal(first, ((FirstRoutableView)host.Content).ViewModel);
 
             var second = new SecondRoutableViewModel();
-            screen.Router.Navigate
-                .Execute(second)
-                .Subscribe();
+            screen.Router.Navigate.Execute(second).Subscribe();
 
             Assert.NotNull(host.Content);
-            Assert.Equal(typeof(SecondRoutableView), host.Content.GetType());
+            Assert.IsType<SecondRoutableView>(host.Content);
             Assert.Equal(second, ((SecondRoutableView)host.Content).DataContext);
             Assert.Equal(second, ((SecondRoutableView)host.Content).ViewModel);
 
-            screen.Router.NavigateBack
-                .Execute(Unit.Default)
-                .Subscribe();
+            screen.Router.NavigateBack.Execute(Unit.Default).Subscribe();
 
             Assert.NotNull(host.Content);
-            Assert.Equal(typeof(FirstRoutableView), host.Content.GetType());
+            Assert.IsType<FirstRoutableView>(host.Content);
             Assert.Equal(first, ((FirstRoutableView)host.Content).DataContext);
             Assert.Equal(first, ((FirstRoutableView)host.Content).ViewModel);
 
-            screen.Router.NavigateBack
-                .Execute(Unit.Default)
-                .Subscribe();
+            screen.Router.NavigateBack.Execute(Unit.Default).Subscribe();
 
             Assert.NotNull(host.Content);
-            Assert.Equal(typeof(TextBlock), host.Content.GetType());
+            Assert.IsType<TextBlock>(host.Content);
             Assert.Equal(defaultContent, host.Content);
         }
 
@@ -121,9 +113,9 @@ namespace Avalonia.ReactiveUI.UnitTests
                 Router = null
             };
 
-            var root = new TestRoot 
-            { 
-                Child = host 
+            var root = new TestRoot
+            {
+                Child = host
             };
 
             Assert.NotNull(host.Content);
@@ -138,9 +130,17 @@ namespace Avalonia.ReactiveUI.UnitTests
             screen.Router.Navigate.Execute(first).Subscribe();
 
             Assert.NotNull(host.Content);
-            Assert.Equal(typeof(FirstRoutableView), host.Content.GetType());
-            Assert.Equal(first, ((FirstRoutableView)host.Content).DataContext);
-            Assert.Equal(first, ((FirstRoutableView)host.Content).ViewModel);
+            Assert.IsType<FirstRoutableView>(host.Content);
+
+            host.Router = null;
+            
+            Assert.NotNull(host.Content);
+            Assert.Equal(defaultContent, host.Content);
+
+            host.Router = screen.Router;
+            
+            Assert.NotNull(host.Content);
+            Assert.IsType<FirstRoutableView>(host.Content);
         }
     }
-}
+}