Make `ViewComponent.View()` overloads respect explicitly passed in model even when `null`

src/Microsoft.AspNetCore.Mvc.ViewFeatures/Controller.cs

@@ -113,7 +113,7 @@ namespace Microsoft.AspNetCore.Mvc
         [NonAction]
         public virtual ViewResult View(string viewName)
         {
-            return View(viewName, model: null);
+            return View(viewName, model: ViewData.Model);
         }
 
         /// <summary>
@@ -138,10 +138,7 @@ namespace Microsoft.AspNetCore.Mvc
         [NonAction]
         public virtual ViewResult View(string viewName, object model)
         {
-            if (model != null)
+            ViewData.Model = model;
-            {
-                ViewData.Model = model;
-            }
 
             return new ViewResult()
             {
@@ -169,7 +166,7 @@ namespace Microsoft.AspNetCore.Mvc
         [NonAction]
         public virtual PartialViewResult PartialView(string viewName)
         {
-            return PartialView(viewName, model: null);
+            return PartialView(viewName, model: ViewData.Model);
         }
 
         /// <summary>
@@ -194,10 +191,7 @@ namespace Microsoft.AspNetCore.Mvc
         [NonAction]
         public virtual PartialViewResult PartialView(string viewName, object model)
         {
-            if (model != null)
+            ViewData.Model = model;
-            {
-                ViewData.Model = model;
-            }
 
             return new PartialViewResult()
             {

src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewComponent.cs

@@ -237,7 +237,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <returns>A <see cref="ViewViewComponentResult"/>.</returns>
         public ViewViewComponentResult View()
         {
-            return View<object>(null, null);
+            return View(viewName: null);
         }
 
         /// <summary>
@@ -247,7 +247,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <returns>A <see cref="ViewViewComponentResult"/>.</returns>
         public ViewViewComponentResult View(string viewName)
         {
-            return View<object>(viewName, null);
+            return View(viewName, ViewData.Model);
         }
 
         /// <summary>
@@ -257,7 +257,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <returns>A <see cref="ViewViewComponentResult"/>.</returns>
         public ViewViewComponentResult View<TModel>(TModel model)
         {
-            return View(null, model);
+            return View(viewName: null, model: model);
         }
 
         /// <summary>
@@ -268,12 +268,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <returns>A <see cref="ViewViewComponentResult"/>.</returns>
         public ViewViewComponentResult View<TModel>(string viewName, TModel model)
         {
-            if (model != null)
+            var viewData = new ViewDataDictionary<TModel>(ViewData, model);
-            {
-                ViewData.Model = model;
-            }
-
-            var viewData = new ViewDataDictionary<TModel>(ViewData);
             return new ViewViewComponentResult
             {
                 ViewEngine = ViewEngine,

test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ControllerTest.cs

@@ -87,6 +87,30 @@ namespace Microsoft.AspNetCore.Mvc.Test
             Assert.Null(actualViewResult.ViewData.Model);
         }
 
+        [Fact]
+        public void Controller_View_WithoutParameter_MaintainsModelInViewData()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+
+            var model = new object();
+            controller.ViewData.Model = model;
+
+            // Act
+            var actualViewResult = controller.View();
+
+            // Assert
+            Assert.IsType<ViewResult>(actualViewResult);
+            Assert.Null(actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Same(model, actualViewResult.ViewData.Model);
+        }
+
         [Fact]
         public void Controller_View_WithParameterViewName_SetsResultViewNameAndNullViewDataModelAndSameTempData()
         {
@@ -152,6 +176,141 @@ namespace Microsoft.AspNetCore.Mvc.Test
             Assert.Same(model, actualViewResult.ViewData.Model);
         }
 
+        [Fact]
+        public void Controller_View_WithNullModelParameter_OverwritesViewDataModel()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+            controller.ViewData.Model = new object();
+
+            // Act
+            var actualViewResult = controller.View(model: null);
+
+            // Assert
+            Assert.IsType<ViewResult>(actualViewResult);
+            Assert.Null(actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Null(actualViewResult.ViewData.Model);
+        }
+
+        [Fact]
+        public void Controller_PartialView_WithoutParameter_MaintainsModelInViewData()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+
+            var model = new object();
+            controller.ViewData.Model = model;
+
+            // Act
+            var actualViewResult = controller.PartialView();
+
+            // Assert
+            Assert.IsType<PartialViewResult>(actualViewResult);
+            Assert.Null(actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Same(model, actualViewResult.ViewData.Model);
+        }
+
+        [Fact]
+        public void Controller_PartialView_WithParameterViewName_SetsResultViewNameAndMaintainsSameViewDataModelAndTempData()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+            var model = new object();
+            controller.ViewData.Model = model;
+
+            // Act
+            var actualViewResult = controller.PartialView("CustomViewName");
+
+            // Assert
+            Assert.IsType<PartialViewResult>(actualViewResult);
+            Assert.Equal("CustomViewName", actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Same(model, actualViewResult.ViewData.Model);
+        }
+
+        [Fact]
+        public void Controller_PartialView_WithParameterViewModel_SetsResultNullViewNameAndViewDataModelAndSameTempData()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+            var model = new object();
+
+            // Act
+            var actualViewResult = controller.PartialView(model);
+
+            // Assert
+            Assert.IsType<PartialViewResult>(actualViewResult);
+            Assert.Null(actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Same(model, actualViewResult.ViewData.Model);
+        }
+
+        [Fact]
+        public void Controller_PartialView_WithParameterViewNameAndViewModel_SetsResultViewNameAndViewDataModelAndSameTempData()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+            var model = new object();
+
+            // Act
+            var actualViewResult = controller.PartialView("CustomViewName", model);
+
+            // Assert
+            Assert.IsType<PartialViewResult>(actualViewResult);
+            Assert.Equal("CustomViewName", actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Same(model, actualViewResult.ViewData.Model);
+        }
+
+        [Fact]
+        public void Controller_PartialView_WithNullModelParameter_OverwritesViewDataModel()
+        {
+            // Arrange
+            var controller = new TestableController()
+            {
+                ViewData = new ViewDataDictionary(new EmptyModelMetadataProvider()),
+                TempData = new TempDataDictionary(new DefaultHttpContext(), Mock.Of<ITempDataProvider>()),
+            };
+            controller.ViewData.Model = new object();
+
+            // Act
+            var actualViewResult = controller.PartialView(model: null);
+
+            // Assert
+            Assert.IsType<PartialViewResult>(actualViewResult);
+            Assert.Null(actualViewResult.ViewName);
+            Assert.Same(controller.ViewData, actualViewResult.ViewData);
+            Assert.Same(controller.TempData, actualViewResult.TempData);
+            Assert.Null(actualViewResult.ViewData.Model);
+        }
+
         [Fact]
         public void Controller_Json_WithParameterValue_SetsResultData()
         {

test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewComponentTests.cs

@@ -139,6 +139,64 @@ namespace Microsoft.AspNetCore.Mvc
             Assert.Null(actualResult.ViewName);
         }
 
+        [Fact]
+        public void ViewComponent_View_WithNullModelParameter_SetsResultViewWithDefaultViewNameAndNullModel()
+        {
+            // Arrange
+            var viewComponent = new TestViewComponent();
+            viewComponent.ViewData.Model = new object();
+            object model = null;
+
+            // Act
+            var actualResult = viewComponent.View(model: model);
+
+            // Assert
+            Assert.IsType<ViewViewComponentResult>(actualResult);
+            Assert.IsType<ViewDataDictionary<object>>(actualResult.ViewData);
+            Assert.NotSame(viewComponent.ViewData, actualResult.ViewData);
+            Assert.Equal(new ViewDataDictionary<object>(viewComponent.ViewData), actualResult.ViewData);
+            Assert.Null(actualResult.ViewData.Model);
+            Assert.Null(actualResult.ViewName);
+        }
+
+        [Fact]
+        public void ViewComponent_View_WithViewNameAndNullModelParameter_SetsResultViewWithViewNameAndNullModel()
+        {
+            // Arrange
+            var viewComponent = new TestViewComponent();
+            viewComponent.ViewData.Model = new object();
+
+            // Act
+            var actualResult = viewComponent.View<object>("CustomViewName", model: null);
+
+            // Assert
+            Assert.IsType<ViewViewComponentResult>(actualResult);
+            Assert.IsType<ViewDataDictionary<object>>(actualResult.ViewData);
+            Assert.NotSame(viewComponent.ViewData, actualResult.ViewData);
+            Assert.Equal(new ViewDataDictionary<object>(viewComponent.ViewData), actualResult.ViewData);
+            Assert.Null(actualResult.ViewData.Model);
+            Assert.Equal("CustomViewName", actualResult.ViewName);
+        }
+
+        [Fact]
+        public void ViewComponent_View_WithViewNameAndNonObjectNullModelParameter_SetsResultViewWithViewNameAndNullModel()
+        {
+            // Arrange
+            var viewComponent = new TestViewComponent();
+            viewComponent.ViewData.Model = "Hello World!";
+
+            // Act
+            var actualResult = viewComponent.View<string>("CustomViewName", model: null);
+
+            // Assert
+            Assert.IsType<ViewViewComponentResult>(actualResult);
+            Assert.IsType<ViewDataDictionary<string>>(actualResult.ViewData);
+            Assert.NotSame(viewComponent.ViewData, actualResult.ViewData);
+            Assert.Equal(new ViewDataDictionary<string>(viewComponent.ViewData), actualResult.ViewData);
+            Assert.Null(actualResult.ViewData.Model);
+            Assert.Equal("CustomViewName", actualResult.ViewName);
+        }
+
         [Fact]
         public void ViewComponent_View_WithViewNameAndModelParameters_SetsResultViewWithCustomViewNameAndModel()
         {