From 2d32420f01f3a755c068b68d4162e30b1bdaa003 Mon Sep 17 00:00:00 2001
From: Doug Bunting <dougbu@microsoft.com>
Date: Fri, 7 Nov 2014 14:08:00 -0800
Subject: [PATCH] Add `<option/>` tag helper - #1423

---
 .../OptionTagHelper.cs                        |  99 +++++++
 .../OptionTagHelperTest.cs                    | 255 ++++++++++++++++++
 2 files changed, 354 insertions(+)
 create mode 100644 src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs
 create mode 100644 test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs

diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs
new file mode 100644
index 0000000000..b1701904dc
--- /dev/null
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/OptionTagHelper.cs
@@ -0,0 +1,99 @@
+// 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 System.Collections.Generic;
+using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+using Microsoft.AspNet.Razor.TagHelpers;
+
+namespace Microsoft.AspNet.Mvc.TagHelpers
+{
+    /// <summary>
+    /// <see cref="ITagHelper"/> implementation targeting &lt;option&gt; elements.
+    /// </summary>
+    /// <remarks>
+    /// This <see cref="ITagHelper"/> works in conjunction with <see cref="SelectTagHelper"/>. It has
+    /// <see cref="ContentBehavior.Modify"/> in order to read element's content but does not modify that content. The
+    /// only modification it makes is to add a <c>selected</c> attribute in some cases.
+    /// </remarks>
+    [ContentBehavior(ContentBehavior.Modify)]
+    public class OptionTagHelper : TagHelper
+    {
+        // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
+        [Activate]
+        protected internal IHtmlGenerator Generator { get; set; }
+
+        // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
+        [Activate]
+        protected internal ViewContext ViewContext { get; set; }
+
+        /// <summary>
+        /// Specifies that this &lt;option&gt; is pre-selected.
+        /// </summary>
+        /// <remarks>
+        /// Passed through to the generated HTML in all cases.
+        /// </remarks>
+        public string Selected { get; set; }
+
+        /// <summary>
+        /// Specifies a value for the &lt;option&gt; element.
+        /// </summary>
+        /// <remarks>
+        /// Passed through to the generated HTML in all cases.
+        /// </remarks>
+        public string Value { get; set; }
+
+        /// <inheritdoc />
+        /// <remarks>
+        /// Does nothing unless <see cref="FormContext.FormData"/> contains a
+        /// <see cref="SelectTagHelper.SelectedValuesFormDataKey"/> entry and that entry is a non-empty
+        /// <see cref="ICollection{string}"/> instance. Also does nothing if the associated &lt;option&gt; is already
+        /// selected.
+        /// </remarks>
+        public override void Process(TagHelperContext context, TagHelperOutput output)
+        {
+            // Pass through attributes that are also well-known HTML attributes.
+            if (Value != null)
+            {
+                output.CopyHtmlAttribute(nameof(Value), context);
+            }
+
+            if (Selected != null)
+            {
+                // This <option/> will always be selected.
+                output.CopyHtmlAttribute(nameof(Selected), context);
+            }
+            else
+            {
+                // Is this <option/> element a child of a <select/> element the SelectTagHelper targeted?
+                object formDataEntry;
+                ViewContext.FormContext.FormData.TryGetValue(
+                    SelectTagHelper.SelectedValuesFormDataKey,
+                    out formDataEntry);
+
+                // ... And did the SelectTagHelper determine any selected values?
+                var selectedValues = formDataEntry as ICollection<string>;
+                if (selectedValues != null && selectedValues.Count != 0)
+                {
+                    // Encode all selected values for comparison with element content.
+                    var encodedValues = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+                    foreach (var selectedValue in selectedValues)
+                    {
+                        encodedValues.Add(Generator.Encode(selectedValue));
+                    }
+
+                    // Select this <option/> element if value attribute or content matches a selected value. Callers
+                    // encode values as-needed before setting TagHelperOutput.Content. But TagHelperOutput itself
+                    // encodes attribute values later, when GenerateStartTag() is called.
+                    var text = output.Content;
+                    var selected = (Value != null) ? selectedValues.Contains(Value) : encodedValues.Contains(text);
+                    if (selected)
+                    {
+                        output.Attributes.Add("selected", "selected");
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs
new file mode 100644
index 0000000000..a4a13790e5
--- /dev/null
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/OptionTagHelperTest.cs
@@ -0,0 +1,255 @@
+// 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.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.TagHelpers
+{
+    public class OptionTagHelperTest
+    {
+        // Original content, selected attribute, value attribute, selected values (to place in FormContext.FormData)
+        // and expected output (concatenation of TagHelperOutput generations).
+        public static TheoryData<string, string, string, ICollection<string>, string> GeneratesExpectedDataSet
+        {
+            get
+            {
+                return new TheoryData<string, string, string, ICollection<string>, string>
+                {
+                    { null, null, null, null,
+                        "<not-option label=\"my-label\"></not-option>" },
+                    { null, string.Empty, "value", null,
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"\"></not-option>" },
+                    { null, "selected", "value", null,
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"selected\"></not-option>" },
+                    { null, null, "value", new string[0],
+                        "<not-option label=\"my-label\" value=\"value\"></not-option>" },
+                    { null, null, "value", new [] { string.Empty, },
+                        "<not-option label=\"my-label\" value=\"value\"></not-option>" },
+                    { null, string.Empty, "value", new [] { string.Empty, },
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"\"></not-option>" },
+                    { null, null, "value", new [] { "value", },
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"selected\"></not-option>" },
+                    { null, null, "value", new [] { string.Empty, "value", },
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"selected\"></not-option>" },
+
+                    { string.Empty, null, null, null,
+                        "<not-option label=\"my-label\"></not-option>" },
+                    { string.Empty, string.Empty, null, null,
+                        "<not-option label=\"my-label\" selected=\"\"></not-option>" },
+                    { string.Empty, "selected", null, null,
+                        "<not-option label=\"my-label\" selected=\"selected\"></not-option>" },
+                    { string.Empty, null, null, new string[0],
+                        "<not-option label=\"my-label\"></not-option>" },
+                    { string.Empty, null, null, new [] { string.Empty, },
+                        "<not-option label=\"my-label\" selected=\"selected\"></not-option>" },
+                    { string.Empty, string.Empty, null, new [] { string.Empty, },
+                        "<not-option label=\"my-label\" selected=\"\"></not-option>" },
+                    { string.Empty, null, null, new [] { "text", },
+                        "<not-option label=\"my-label\"></not-option>" },
+                    { string.Empty, null, null, new [] { string.Empty, "text", },
+                        "<not-option label=\"my-label\" selected=\"selected\"></not-option>" },
+
+                    { "text", null, null, null,
+                        "<not-option label=\"my-label\">text</not-option>" },
+                    { "text", string.Empty, null, null,
+                        "<not-option label=\"my-label\" selected=\"\">text</not-option>" },
+                    { "text", "selected", null, null,
+                        "<not-option label=\"my-label\" selected=\"selected\">text</not-option>" },
+                    { "text", null, null, new string[0],
+                        "<not-option label=\"my-label\">text</not-option>" },
+                    { "text", null, null, new [] { string.Empty, },
+                        "<not-option label=\"my-label\">text</not-option>" },
+                    { "text", null, null, new [] { "text", },
+                        "<not-option label=\"my-label\" selected=\"selected\">text</not-option>" },
+                    { "text", string.Empty, null, new [] { "text", },
+                        "<not-option label=\"my-label\" selected=\"\">text</not-option>" },
+                    { "text", null, null, new [] { string.Empty, "text", },
+                        "<not-option label=\"my-label\" selected=\"selected\">text</not-option>" },
+
+                    { "text", string.Empty, "value", null,
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"\">text</not-option>" },
+                    { "text", "selected", "value", null,
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"selected\">text</not-option>" },
+                    { "text", null, "value", new string[0],
+                        "<not-option label=\"my-label\" value=\"value\">text</not-option>" },
+                    { "text", null, "value", new [] { string.Empty, },
+                        "<not-option label=\"my-label\" value=\"value\">text</not-option>" },
+                    { "text", string.Empty, "value", new [] { string.Empty, },
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"\">text</not-option>" },
+                    { "text", null, "value", new [] { "text", },
+                        "<not-option label=\"my-label\" value=\"value\">text</not-option>" },
+                    { "text", null, "value", new [] { "value", },
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"selected\">text</not-option>" },
+                    { "text", null, "value", new [] { string.Empty, "value", },
+                        "<not-option label=\"my-label\" value=\"value\" selected=\"selected\">text</not-option>" },
+                };
+            }
+        }
+
+        // Original content, selected attribute, value attribute, selected values (to place in FormContext.FormData)
+        // and expected output (concatenation of TagHelperOutput generations). Excludes non-null selected attribute,
+        // null selected values, and empty selected values cases.
+        public static IEnumerable<object []> DoesNotUseGeneratorDataSet
+        {
+            get
+            {
+                return GeneratesExpectedDataSet.Where(
+                    entry => (entry[1] != null || entry[3] == null || (entry[3] as ICollection<string>).Count == 0));
+            }
+        }
+
+        // Original content, selected attribute, value attribute, selected values (to place in FormContext.FormData)
+        // and expected output (concatenation of TagHelperOutput generations). Excludes non-null selected attribute
+        // cases.
+        public static IEnumerable<object[]> DoesNotUseViewContextDataSet
+        {
+            get
+            {
+                return GeneratesExpectedDataSet.Where(entry => entry[1] != null);
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(GeneratesExpectedDataSet))]
+        public async Task ProcessAsync_GeneratesExpectedOutput(
+            string originalContent,
+            string selected,
+            string value,
+            ICollection<string> selectedValues,
+            string expectedOutput)
+        {
+            // Arrange
+            var originalAttributes = new Dictionary<string, string>
+            {
+                { "label", "my-label" },
+            };
+            var originalTagName = "not-option";
+
+            var contextAttributes = new Dictionary<string, object>
+            {
+                { "label", "my-label" },
+                { "selected", selected },
+                { "value", value },
+            };
+            var tagHelperContext = new TagHelperContext(contextAttributes);
+            var output = new TagHelperOutput(originalTagName, originalAttributes, originalContent)
+            {
+                SelfClosing = false,
+            };
+
+            var metadataProvider = new EmptyModelMetadataProvider();
+            var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
+            var viewContext = TestableHtmlGenerator.GetViewContext(
+                model: null,
+                htmlGenerator: htmlGenerator,
+                metadataProvider: metadataProvider);
+            viewContext.FormContext.FormData[SelectTagHelper.SelectedValuesFormDataKey] = selectedValues;
+            var tagHelper = new OptionTagHelper
+            {
+                Generator = htmlGenerator,
+                Selected = selected,
+                Value = value,
+                ViewContext = viewContext,
+            };
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            Assert.Equal(
+                expectedOutput,
+                output.GenerateStartTag() + output.GenerateContent() + output.GenerateEndTag());
+        }
+
+        [Theory]
+        [MemberData(nameof(DoesNotUseGeneratorDataSet))]
+        public async Task ProcessAsync_DoesNotUseGenerator_IfSelectedNullOrNoSelectedValues(
+            string originalContent,
+            string selected,
+            string value,
+            ICollection<string> selectedValues,
+            string ignored)
+        {
+            // Arrange
+            var originalAttributes = new Dictionary<string, string>
+            {
+                { "label", "my-label" },
+            };
+            var originalTagName = "not-option";
+
+            var contextAttributes = new Dictionary<string, object>
+            {
+                { "label", "my-label" },
+                { "selected", selected },
+                { "value", value },
+            };
+            var tagHelperContext = new TagHelperContext(contextAttributes);
+            var output = new TagHelperOutput(originalTagName, originalAttributes, originalContent)
+            {
+                SelfClosing = false,
+            };
+
+            var metadataProvider = new EmptyModelMetadataProvider();
+            var htmlGenerator = new TestableHtmlGenerator(metadataProvider);
+            var viewContext = TestableHtmlGenerator.GetViewContext(
+                model: null,
+                htmlGenerator: htmlGenerator,
+                metadataProvider: metadataProvider);
+            viewContext.FormContext.FormData[SelectTagHelper.SelectedValuesFormDataKey] = selectedValues;
+            var tagHelper = new OptionTagHelper
+            {
+                Selected = selected,
+                Value = value,
+                ViewContext = viewContext,
+            };
+
+            // Act & Assert
+            // Tag helper would throw an NRE if it used Generator value.
+            await Assert.DoesNotThrowAsync(() => tagHelper.ProcessAsync(tagHelperContext, output));
+        }
+
+        [Theory]
+        [MemberData(nameof(DoesNotUseViewContextDataSet))]
+        public async Task ProcessAsync_DoesNotUseViewContext_IfSelectedNotNull(
+            string originalContent,
+            string selected,
+            string value,
+            ICollection<string> ignoredValues,
+            string ignoredOutput)
+        {
+            // Arrange
+            var originalAttributes = new Dictionary<string, string>
+            {
+                { "label", "my-label" },
+            };
+            var originalTagName = "not-option";
+
+            var contextAttributes = new Dictionary<string, object>
+            {
+                { "label", "my-label" },
+                { "selected", selected },
+                { "value", value },
+            };
+            var tagHelperContext = new TagHelperContext(contextAttributes);
+            var output = new TagHelperOutput(originalTagName, originalAttributes, originalContent)
+            {
+                SelfClosing = false,
+            };
+
+            var tagHelper = new OptionTagHelper
+            {
+                Selected = selected,
+                Value = value,
+            };
+
+            // Act & Assert
+            // Tag helper would throw an NRE if it used ViewContext or Generator values.
+            await Assert.DoesNotThrowAsync(() => tagHelper.ProcessAsync(tagHelperContext, output));
+        }
+    }
+}