ViewViewComponentResult doesn't handle `~/` in view paths correctly

Fixes #2856

src/Microsoft.AspNet.Mvc.ViewFeatures/ViewComponents/ViewViewComponentResult.cs

@@ -5,7 +5,6 @@ using System;
 using System.Globalization;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc.Rendering;
-using Microsoft.AspNet.Mvc.ViewComponents;
 using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 
@@ -18,6 +17,7 @@ namespace Microsoft.AspNet.Mvc
     {
         // {0} is the component name, {1} is the view name.
         private const string ViewPathFormat = "Components/{0}/{1}";
+        private const string DefaultViewName = "Default";
 
         /// <summary>
         /// Gets or sets the view name.
@@ -63,9 +63,11 @@ namespace Microsoft.AspNet.Mvc
         {
             var viewEngine = ViewEngine ?? ResolveViewEngine(context);
             var viewData = ViewData ?? context.ViewData;
+            var isNullOrEmptyViewName = string.IsNullOrEmpty(ViewName);
 
             string qualifiedViewName;
-            if (ViewName != null && ViewName.Length > 0 && ViewName[0] == '/')
+            if (!isNullOrEmptyViewName &&
+                (ViewName[0] == '~' || ViewName[0] == '/'))
             {
                 // View name that was passed in is already a rooted path, the view engine will handle this.
                 qualifiedViewName = ViewName;
@@ -83,11 +85,13 @@ namespace Microsoft.AspNet.Mvc
                 //  Areas/Blog/Views/Shared/Components/Cart/Default.cshtml
                 //
                 // This supports a controller or area providing an override for component views.
+                var viewName = isNullOrEmptyViewName ? DefaultViewName : ViewName;
+
                 qualifiedViewName = string.Format(
                     CultureInfo.InvariantCulture,
                     ViewPathFormat,
                     context.ViewComponentDescriptor.ShortName,
-                    ViewName ?? "Default");
+                    viewName);
             }
 
             var view = FindView(context.ViewContext, viewEngine, qualifiedViewName);

test/Microsoft.AspNet.Mvc.ViewFeatures.Test/ViewComponents/ViewViewComponentResultTest.cs

@@ -275,22 +275,53 @@ namespace Microsoft.AspNet.Mvc
             Assert.Equal(expected, ex.Message);
         }
 
-        [Fact]
+        [Theory]
-        public void Execute_CallsFindPartialView_WithExpectedPath()
+        [InlineData(null)]
+        [InlineData("")]
+        public void Execute_CallsFindPartialView_WithExpectedPath_WhenViewNameIsNullOrEmpty(string viewName)
+        {
+            // Arrange
+            var shortName = "SomeShortName";
+            var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider());
+            var componentContext = GetViewComponentContext(new Mock<IView>().Object, viewData);
+            componentContext.ViewComponentDescriptor.ShortName = shortName;
+            var expectedViewName = $"Components/{shortName}/Default";
+            var viewEngine = new Mock<ICompositeViewEngine>(MockBehavior.Strict);
+            viewEngine
+                .Setup(v => v.FindPartialView(It.IsAny<ActionContext>(), expectedViewName))
+                .Returns(ViewEngineResult.Found(string.Empty, new Mock<IView>().Object))
+                .Verifiable();
+
+            var componentResult = new ViewViewComponentResult();
+            componentResult.ViewEngine = viewEngine.Object;
+            componentResult.ViewData = viewData;
+            componentResult.ViewName = viewName;
+
+            // Act & Assert
+            componentResult.Execute(componentContext);
+            viewEngine.Verify();
+        }
+
+        [Theory]
+        [InlineData("~/Home/Index/MyViewComponent1.cshtml")]
+        [InlineData("~MyViewComponent2.cshtml")]
+        [InlineData("/MyViewComponent3.cshtml")]
+        public void Execute_CallsFindPartialView_WithExpectedPath_WhenViewNameIsSpecified(string viewName)
         {
             // Arrange
             var viewEngine = new Mock<ICompositeViewEngine>(MockBehavior.Strict);
             viewEngine
-                .Setup(v => v.FindPartialView(It.IsAny<ActionContext>(), 
+                .Setup(v => v.FindPartialView(It.IsAny<ActionContext>(), viewName))
-                                              It.Is<string>(view => view.Contains("Components"))))
                 .Returns(ViewEngineResult.Found(string.Empty, new Mock<IView>().Object))
                 .Verifiable();
-
             var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider());
             var componentContext = GetViewComponentContext(new Mock<IView>().Object, viewData);
-            var componentResult = new ViewViewComponentResult();
+            var componentResult = new ViewViewComponentResult
-            componentResult.ViewEngine = viewEngine.Object;
+            {
-            componentResult.ViewData = viewData;
+                ViewEngine = viewEngine.Object,
+                ViewData = viewData,
+                ViewName = viewName
+            };
 
             // Act & Assert
             componentResult.Execute(componentContext);