From c9c8e802a7ead380fcc60c6c7baa5924e8713db8 Mon Sep 17 00:00:00 2001
From: "N. Taylor Mullen" <nimullen@microsoft.com>
Date: Mon, 13 Apr 2015 12:22:25 -0700
Subject: [PATCH] Add PreElement and PostElement to TagHelperOutput.

- These two new properties will enable TagHelper authors to render content before and after the TagHelper's HTML element.
- Added tests to correspond with existing test coverage.
- Modified existing tests to double check for TagHelperOutput.Pre/PostElement.
- Refactored all DefaultTagHelperContent pieces of TagHelperOutput to be get only properties.

#341
---
 .../TagHelpers/TagHelperOutput.cs             | 49 +++++++------------
 .../TagHelpers/TagHelperOutputTest.cs         | 48 +++++++++++++++++-
 2 files changed, 66 insertions(+), 31 deletions(-)

diff --git a/src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperOutput.cs b/src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperOutput.cs
index 6da8128e25..0d6d0d33e6 100644
--- a/src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperOutput.cs
+++ b/src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperOutput.cs
@@ -12,10 +12,6 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
     /// </summary>
     public class TagHelperOutput
     {
-        private readonly DefaultTagHelperContent _preContent;
-        private readonly DefaultTagHelperContent _content;
-        private readonly DefaultTagHelperContent _postContent;
-
         // Internal for testing
         internal TagHelperOutput(string tagName)
             : this(tagName, new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase))
@@ -33,9 +29,6 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         {
             TagName = tagName;
             Attributes = new Dictionary<string, object>(attributes, StringComparer.OrdinalIgnoreCase);
-            _preContent = new DefaultTagHelperContent();
-            _content = new DefaultTagHelperContent();
-            _postContent = new DefaultTagHelperContent();
         }
 
         /// <summary>
@@ -46,42 +39,36 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         /// </remarks>
         public string TagName { get; set; }
 
+        /// <summary>
+        /// Content that precedes the HTML element.
+        /// </summary>
+        /// <remarks>Value is rendered before the HTML element.</remarks>
+        public TagHelperContent PreElement { get; } = new DefaultTagHelperContent();
+
         /// <summary>
         /// The HTML element's pre content.
         /// </summary>
         /// <remarks>Value is prepended to the <see cref="ITagHelper"/>'s final output.</remarks>
-        public TagHelperContent PreContent
-        {
-            get
-            {
-                return _preContent;
-            }
-        }
+        public TagHelperContent PreContent { get; } = new DefaultTagHelperContent();
 
         /// <summary>
         /// The HTML element's main content.
         /// </summary>
         /// <remarks>Value occurs in the <see cref="ITagHelper"/>'s final output after <see cref="PreContent"/> and
         /// before <see cref="PostContent"/></remarks>
-        public TagHelperContent Content
-        {
-            get
-            {
-                return _content;
-            }
-        }
+        public TagHelperContent Content { get; } = new DefaultTagHelperContent();
 
         /// <summary>
         /// The HTML element's post content.
         /// </summary>
         /// <remarks>Value is appended to the <see cref="ITagHelper"/>'s final output.</remarks>
-        public TagHelperContent PostContent
-        {
-            get
-            {
-                return _postContent;
-            }
-        }
+        public TagHelperContent PostContent { get; } = new DefaultTagHelperContent();
+
+        /// <summary>
+        /// Content that follows the HTML element.
+        /// </summary>
+        /// <remarks>Value is rendered after the HTML element.</remarks>
+        public TagHelperContent PostElement { get; } = new DefaultTagHelperContent();
 
         /// <summary>
         /// <c>true</c> if <see cref="Content"/> has been set, <c>false</c> otherwise.
@@ -113,15 +100,17 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         /// Changes <see cref="TagHelperOutput"/> to generate nothing.
         /// </summary>
         /// <remarks>
-        /// Sets <see cref="TagName"/> to <c>null</c>, and clears <see cref="PreContent"/>, <see cref="Content"/>,
-        /// and <see cref="PostContent"/> to suppress output.
+        /// Sets <see cref="TagName"/> to <c>null</c>, and clears <see cref="PreElement"/>, <see cref="PreContent"/>, 
+        /// <see cref="Content"/>, <see cref="PostContent"/>, and <see cref="PostElement"/> to suppress output.
         /// </remarks>
         public void SuppressOutput()
         {
             TagName = null;
+            PreElement.Clear();
             PreContent.Clear();
             Content.Clear();
             PostContent.Clear();
+            PostElement.Clear();
         }
     }
 }
\ No newline at end of file
diff --git a/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperOutputTest.cs b/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperOutputTest.cs
index f100c90fe0..39d7912f13 100644
--- a/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperOutputTest.cs
+++ b/test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperOutputTest.cs
@@ -8,6 +8,38 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
     public class TagHelperOutputTest
     {
+        [Fact]
+        public void PreElement_SetContent_ChangesValue()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p");
+            tagHelperOutput.PreElement.SetContent("Hello World");
+
+            // Act & Assert
+            Assert.NotNull(tagHelperOutput.PreElement);
+            Assert.NotNull(tagHelperOutput.PreContent);
+            Assert.NotNull(tagHelperOutput.Content);
+            Assert.NotNull(tagHelperOutput.PostContent);
+            Assert.NotNull(tagHelperOutput.PostElement);
+            Assert.Equal("Hello World", tagHelperOutput.PreElement.GetContent());
+        }
+
+        [Fact]
+        public void PostElement_SetContent_ChangesValue()
+        {
+            // Arrange
+            var tagHelperOutput = new TagHelperOutput("p");
+            tagHelperOutput.PostElement.SetContent("Hello World");
+
+            // Act & Assert
+            Assert.NotNull(tagHelperOutput.PreElement);
+            Assert.NotNull(tagHelperOutput.PreContent);
+            Assert.NotNull(tagHelperOutput.Content);
+            Assert.NotNull(tagHelperOutput.PostContent);
+            Assert.NotNull(tagHelperOutput.PostElement);
+            Assert.Equal("Hello World", tagHelperOutput.PostElement.GetContent());
+        }
+
         [Fact]
         public void TagName_CanSetToNullInCtor()
         {
@@ -39,9 +71,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             tagHelperOutput.PreContent.SetContent("Hello World");
 
             // Act & Assert
+            Assert.NotNull(tagHelperOutput.PreElement);
             Assert.NotNull(tagHelperOutput.PreContent);
             Assert.NotNull(tagHelperOutput.Content);
             Assert.NotNull(tagHelperOutput.PostContent);
+            Assert.NotNull(tagHelperOutput.PostElement);
             Assert.Equal("Hello World", tagHelperOutput.PreContent.GetContent());
         }
 
@@ -53,9 +87,11 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             tagHelperOutput.Content.SetContent("Hello World");
 
             // Act & Assert
+            Assert.NotNull(tagHelperOutput.PreElement);
             Assert.NotNull(tagHelperOutput.PreContent);
             Assert.NotNull(tagHelperOutput.Content);
             Assert.NotNull(tagHelperOutput.PostContent);
+            Assert.NotNull(tagHelperOutput.PostElement);
             Assert.Equal("Hello World", tagHelperOutput.Content.GetContent());
         }
 
@@ -67,14 +103,16 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             tagHelperOutput.PostContent.SetContent("Hello World");
 
             // Act & Assert
+            Assert.NotNull(tagHelperOutput.PreElement);
             Assert.NotNull(tagHelperOutput.PreContent);
             Assert.NotNull(tagHelperOutput.Content);
             Assert.NotNull(tagHelperOutput.PostContent);
+            Assert.NotNull(tagHelperOutput.PostElement);
             Assert.Equal("Hello World", tagHelperOutput.PostContent.GetContent());
         }
 
         [Fact]
-        public void SuppressOutput_Sets_TagName_Content_PreContent_PostContent_ToNull()
+        public void SuppressOutput_Sets_AllContent_ToNullOrEmpty()
         {
             // Arrange
             var tagHelperOutput = new TagHelperOutput("p");
@@ -87,12 +125,16 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             Assert.Null(tagHelperOutput.TagName);
+            Assert.NotNull(tagHelperOutput.PreElement);
+            Assert.Empty(tagHelperOutput.PreElement.GetContent());
             Assert.NotNull(tagHelperOutput.PreContent);
             Assert.Empty(tagHelperOutput.PreContent.GetContent());
             Assert.NotNull(tagHelperOutput.Content);
             Assert.Empty(tagHelperOutput.Content.GetContent());
             Assert.NotNull(tagHelperOutput.PostContent);
             Assert.Empty(tagHelperOutput.PostContent.GetContent());
+            Assert.NotNull(tagHelperOutput.PostElement);
+            Assert.Empty(tagHelperOutput.PostElement.GetContent());
         }
 
         [Fact]
@@ -113,12 +155,16 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             tagHelperOutput.SuppressOutput();
 
             // Assert
+            Assert.NotNull(tagHelperOutput.PreElement);
+            Assert.Empty(tagHelperOutput.PreElement.GetContent());
             Assert.NotNull(tagHelperOutput.PreContent);
             Assert.Empty(tagHelperOutput.PreContent.GetContent());
             Assert.NotNull(tagHelperOutput.Content);
             Assert.Empty(tagHelperOutput.Content.GetContent());
             Assert.NotNull(tagHelperOutput.PostContent);
             Assert.Empty(tagHelperOutput.PostContent.GetContent());
+            Assert.NotNull(tagHelperOutput.PostElement);
+            Assert.Empty(tagHelperOutput.PostElement.GetContent());
         }
 
         [Theory]