Add tests to validate attribute value rendering.

- Exposed internals from Mvc.Razor.Host to Mvc.Razor.Test so it can use the MvcRazorHost override that takes the IFileSystem.
- Added end-to-end code generation tests for TagHelpers with ModelExpression properties.

#1241

Author: N. Taylor Mullen

test/Microsoft.AspNet.Mvc.Razor.Host.Test/CommonTagHelpers.cs

@@ -0,0 +1,24 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    public class InputTestTagHelper : TagHelper
+    {
+        public ModelExpression For { get; set; }
+    }
+}
+
+namespace Microsoft.AspNet.Mvc.Rendering
+{
+    // This is here to mimic the ModelExpression type defined in Microsoft.AspNet.Mvc.Core.
+    // Normally it's understood by the MvcRazorHost via a stringified version of it (will change once we have a DTH)
+    // so we need to provide some polyfill so we can test its functionality in Microsoft.AspNet.Mvc.Razor.Host.Test.
+    public class ModelExpression
+    {
+    }
+}

test/Microsoft.AspNet.Mvc.Razor.Host.Test/MvcRazorHostTest.cs

@@ -12,11 +12,44 @@ namespace Microsoft.AspNet.Mvc.Razor
 {
     public class MvcRazorHostTest
     {
+        [Fact]
+        public void MvcRazorHost_GeneratesTagHelperModelExpressionCode_DesignTime()
+        {
+            // Arrange
+            var host = new MvcRazorHost(new TestFileSystem())
+            {
+                DesignTimeMode = true
+            };
+            var expectedLineMappings = new List<LineMapping>
+            {
+                BuildLineMapping(documentAbsoluteIndex: 7, 
+                                 documentLineIndex: 0,
+                                 documentCharacterIndex: 7, 
+                                 generatedAbsoluteIndex: 444,
+                                 generatedLineIndex: 12,
+                                 generatedCharacterIndex: 7, 
+                                 contentLength: 8),
+                BuildLineMapping(documentAbsoluteIndex: 33,
+                                 documentLineIndex: 2,
+                                 documentCharacterIndex: 14,
+                                 generatedAbsoluteIndex: 823,
+                                 generatedLineIndex: 25,
+                                 generatedCharacterIndex: 14,
+                                 contentLength: 85)
+            };
+
+            // Act and Assert
+            RunDesignTimeTest(host, 
+                              testName: "ModelExpressionTagHelper", 
+                              expectedLineMappings: expectedLineMappings);
+        }
+
         [Theory]
         [InlineData("Basic")]
         [InlineData("Inject")]
         [InlineData("InjectWithModel")]
         [InlineData("Model")]
+        [InlineData("ModelExpressionTagHelper")]
         public void MvcRazorHost_ParsesAndGeneratesCodeForBasicScenarios(string scenarioName)
         {
             // Arrange

test/Microsoft.AspNet.Mvc.Razor.Host.Test/MvcTagHelperAttributeValueCodeRendererTest.cs

@@ -0,0 +1,50 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Reflection;
+using Microsoft.AspNet.Razor.Generator;
+using Microsoft.AspNet.Razor.Generator.Compiler.CSharp;
+using Microsoft.AspNet.Razor.TagHelpers;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    public class MvcTagHelperAttributeValueCodeRendererTest
+    {
+        [Theory]
+        [InlineData("SomeType", "SomeType", "SomeMethod(__model => __model.MyValue)")]
+        [InlineData("SomeType", "SomeType2", "MyValue")]
+        public void RenderAttributeValue_RendersModelExpressionsCorrectly(string modelExpressionType,
+                                                                          string propertyType, 
+                                                                          string expectedValue)
+        {
+            // Arrange
+            var renderer = new MvcTagHelperAttributeValueCodeRenderer(
+                new GeneratedTagHelperAttributeContext
+                {
+                    ModelExpressionTypeName = modelExpressionType,
+                    CreateModelExpressionMethodName = "SomeMethod"
+                });
+            var propertyInfo = new Mock<PropertyInfo>();
+            propertyInfo.Setup(mock => mock.PropertyType.FullName).Returns(propertyType);
+            var attributeDescriptor = new TagHelperAttributeDescriptor("MyAttribute", propertyInfo.Object);
+            var writer = new CSharpCodeWriter();
+            var generatorContext = new CodeGeneratorContext(host: null,
+                                                            className: string.Empty,
+                                                            rootNamespace: string.Empty,
+                                                            sourceFile: string.Empty,
+                                                            shouldGenerateLinePragmas: true);
+            var context = new CodeBuilderContext(generatorContext);
+
+            // Act
+            renderer.RenderAttributeValue(attributeDescriptor, writer, context,
+            (codeWriter) => {
+                codeWriter.Write("MyValue");
+            });
+
+            // Assert
+            Assert.Equal(expectedValue, writer.GenerateCode());
+        }
+    }
+}

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Input/ModelExpressionTagHelper.cshtml

@@ -0,0 +1,5 @@
+@model DateTime
+
+@addtaghelper "Microsoft.AspNet.Mvc.Razor.InputTestTagHelper, Microsoft.AspNet.Mvc.Razor.Host.Test"
+
+<inputTest for="Now" />

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/DesignTime/ModelExpressionTagHelper.cs

@@ -0,0 +1,59 @@
+namespace Asp
+{
+    using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+    using System;
+    using System.Linq;
+    using System.Collections.Generic;
+    using Microsoft.AspNet.Mvc;
+    using Microsoft.AspNet.Mvc.Rendering;
+    using System.Threading.Tasks;
+
+    public class ASPV_TestFiles_Input_ModelExpressionTagHelper_cshtml : Microsoft.AspNet.Mvc.Razor.RazorPage<
+#line 1 "TestFiles/Input/ModelExpressionTagHelper.cshtml"
+       DateTime
+
+#line default
+#line hidden
+    >
+    {
+        private static object @__o;
+        private void @__RazorDesignTimeHelpers__()
+        {
+            #pragma warning disable 219
+            string __tagHelperDirectiveSyntaxHelper = null;
+            __tagHelperDirectiveSyntaxHelper = 
+#line 3 "TestFiles/Input/ModelExpressionTagHelper.cshtml"
+              "Microsoft.AspNet.Mvc.Razor.InputTestTagHelper, Microsoft.AspNet.Mvc.Razor.Host.Test"
+
+#line default
+#line hidden
+            ;
+            #pragma warning restore 219
+        }
+        #line hidden
+        private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperExecutionContext __tagHelperExecutionContext = null;
+        private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperRunner __tagHelperRunner = new Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperRunner();
+        private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperScopeManager __tagHelperScopeManager = new Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperScopeManager();
+        private Microsoft.AspNet.Mvc.Razor.InputTestTagHelper __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper = null;
+        #line hidden
+        public ASPV_TestFiles_Input_ModelExpressionTagHelper_cshtml()
+        {
+        }
+        #line hidden
+        [Microsoft.AspNet.Mvc.ActivateAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<DateTime> Html { get; private set; }
+        [Microsoft.AspNet.Mvc.ActivateAttribute]
+        public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
+        [Microsoft.AspNet.Mvc.ActivateAttribute]
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+
+        #line hidden
+
+        #pragma warning disable 1998
+        public override async Task ExecuteAsync()
+        {
+        }
+        #pragma warning restore 1998
+    }
+}

test/Microsoft.AspNet.Mvc.Razor.Host.Test/TestFiles/Output/Runtime/ModelExpressionTagHelper.cs

@@ -0,0 +1,56 @@
+#pragma checksum "TestFiles/Input/ModelExpressionTagHelper.cshtml" "{ff1816ec-aa5e-4d10-87f7-6f4963833460}" "11088b573392b1db9fe4cac4fff3a9ce68a72c40"
+namespace Asp
+{
+    using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+    using System;
+    using System.Linq;
+    using System.Collections.Generic;
+    using Microsoft.AspNet.Mvc;
+    using Microsoft.AspNet.Mvc.Rendering;
+    using System.Threading.Tasks;
+
+    public class ASPV_TestFiles_Input_ModelExpressionTagHelper_cshtml : Microsoft.AspNet.Mvc.Razor.RazorPage<
+#line 1 "TestFiles/Input/ModelExpressionTagHelper.cshtml"
+       DateTime
+
+#line default
+#line hidden
+    >
+    {
+        #line hidden
+        private System.IO.TextWriter __tagHelperStringValueBuffer = null;
+        private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperExecutionContext __tagHelperExecutionContext = null;
+        private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperRunner __tagHelperRunner = new Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperRunner();
+        private Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperScopeManager __tagHelperScopeManager = new Microsoft.AspNet.Razor.Runtime.TagHelpers.TagHelperScopeManager();
+        private Microsoft.AspNet.Mvc.Razor.InputTestTagHelper __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper = null;
+        #line hidden
+        public ASPV_TestFiles_Input_ModelExpressionTagHelper_cshtml()
+        {
+        }
+        #line hidden
+        [Microsoft.AspNet.Mvc.ActivateAttribute]
+        public Microsoft.AspNet.Mvc.Rendering.IHtmlHelper<DateTime> Html { get; private set; }
+        [Microsoft.AspNet.Mvc.ActivateAttribute]
+        public Microsoft.AspNet.Mvc.IViewComponentHelper Component { get; private set; }
+        [Microsoft.AspNet.Mvc.ActivateAttribute]
+        public Microsoft.AspNet.Mvc.IUrlHelper Url { get; private set; }
+
+        #line hidden
+
+        #pragma warning disable 1998
+        public override async Task ExecuteAsync()
+        {
+            WriteLiteral("\r\n");
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("inputTest");
+            __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper = CreateTagHelper<Microsoft.AspNet.Mvc.Razor.InputTestTagHelper>();
+            __tagHelperExecutionContext.Add(__Microsoft_AspNet_Mvc_Razor_InputTestTagHelper);
+            __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For = CreateModelExpression(__model => __model.Now);
+            __tagHelperExecutionContext.AddTagHelperAttribute("For", __Microsoft_AspNet_Mvc_Razor_InputTestTagHelper.For);
+            __tagHelperExecutionContext.Output = __tagHelperRunner.RunAsync(__tagHelperExecutionContext).Result;
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateStartTag());
+            WriteLiteral(__tagHelperExecutionContext.Output.GenerateEndTag());
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+        }
+        #pragma warning restore 1998
+    }
+}