Ability to override view model type used in view resolution using a view model attribute

ReactiveUI.Tests/RxRouting.cs

@@ -34,6 +34,14 @@ public BazViewModel(IScreen hostScreen)
             HostScreen = hostScreen;
         }
     }
+
+    [ViewResolutionTypeOverride(Type = typeof(BazViewModel))]
+    public class BazViewModel<T> : BazViewModel
+    {
+        public BazViewModel(IScreen hostScreen) : base(hostScreen)
+        {
+        }
+    }
 }
 
 namespace Foobar.Views
@@ -80,5 +88,25 @@ public void ResolveExplicitViewType()
                 Assert.True(result is BazView);
             }
         }
+
+        [Fact]
+        public void ResolveViewForGenericViewModelType()
+        {
+            var resolver = new ModernDependencyResolver();
+
+            resolver.InitializeSplat();
+            resolver.InitializeReactiveUI();
+            resolver.Register(() => new BazView(), typeof(IViewFor<BazViewModel>));
+
+            using (resolver.WithResolver())
+            {
+                var fixture = new DefaultViewLocator();
+                var vm = new BazViewModel<int>(null);
+
+                var result = fixture.ResolveView(vm);
+                this.Log().Info(result.GetType().FullName);
+                Assert.True(result is BazView);
+            }
+        }
     }
 }

ReactiveUI/Interfaces.cs

@@ -468,6 +468,20 @@ public class ViewContractAttribute : Attribute
         /// </summary>
         public string Contract { get; set; }
     }
+
+    /// <summary>
+    /// Allows overriding the type information used for view resolution of a view 
+    /// model. This is useful if your view model is a generic type and you would 
+    /// prefer to resolve your view using an interface.
+    /// </summary>
+    public class ViewResolutionTypeOverrideAttribute : Attribute
+    {
+        /// <summary>
+        /// The type that will be used in view resolution instead of the owning 
+        /// view model type
+        /// </summary>
+        public Type Type { get; set; }
+    }
 }
 
 // vim: tw=120 ts=4 sw=4 et :

ReactiveUI/ViewLocator.cs

@@ -50,21 +50,29 @@ public IViewFor ResolveView<T>(T viewModel, string contract = null)
             // * IViewFor<IFooBarViewModel>
             // * IViewFor<FooBarViewModel> (the original behavior in RxUI 3.1)
 
-            var attrs = viewModel.GetType().GetTypeInfo().GetCustomAttributes(typeof (ViewContractAttribute), true);
+            var viewModelType = viewModel.GetType();
+
+            var attrs = viewModelType.GetTypeInfo().GetCustomAttributes(typeof(ViewContractAttribute), true);
 
             if (attrs.Any()) {
                 contract = contract ?? ((ViewContractAttribute) attrs.First()).Contract;
             }
 
+            attrs = viewModelType.GetTypeInfo().GetCustomAttributes(typeof(ViewResolutionTypeOverrideAttribute), true);
+
+            if (attrs.Any()) {
+                viewModelType = ((ViewResolutionTypeOverrideAttribute)attrs.First()).Type;
+            }
+
             // IFooBarView that implements IViewFor (or custom ViewModelToViewFunc)
-            var typeToFind = ViewModelToViewFunc(viewModel.GetType().AssemblyQualifiedName);
+            var typeToFind = ViewModelToViewFunc(viewModelType.AssemblyQualifiedName);
 
             var ret = attemptToResolveView(Reflection.ReallyFindType(typeToFind, false), contract);
             if (ret != null) return ret;
 
             // IViewFor<FooBarViewModel> (the original behavior in RxUI 3.1)
             var viewType = typeof (IViewFor<>);
-            return attemptToResolveView(viewType.MakeGenericType(viewModel.GetType()), contract);
+            return attemptToResolveView(viewType.MakeGenericType(viewModelType), contract);
         }
 
         IViewFor attemptToResolveView(Type type, string contract)