TagHelpers attribute targeting - part 2

src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs

@@ -90,22 +90,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             return string.Format(CultureInfo.CurrentCulture, GetString("InputTagHelper_ValueRequired"), p0, p1, p2, p3);
         }
 
-        /// <summary>
-        /// Cannot determine body for {0}. '{2}' must be null if '{1}' is null.
-        /// </summary>
-        internal static string SelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified
-        {
-            get { return GetString("SelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified"); }
-        }
-
-        /// <summary>
-        /// Cannot determine body for {0}. '{2}' must be null if '{1}' is null.
-        /// </summary>
-        internal static string FormatSelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified(object p0, object p1, object p2)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("SelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified"), p0, p1, p2);
-        }
-
         /// <summary>
         /// The {2} was unable to provide metadata about '{1}' expression value '{3}' for {0}.
         /// </summary>

src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx

@@ -132,9 +132,6 @@
   <data name="InputTagHelper_ValueRequired" xml:space="preserve">
     <value>'{1}' must not be null for {0} if '{2}' is '{3}'.</value>
   </data>
-  <data name="SelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified" xml:space="preserve">
-    <value>Cannot determine body for {0}. '{2}' must be null if '{1}' is null.</value>
-  </data>
   <data name="TagHelpers_NoProvidedMetadata" xml:space="preserve">
     <value>The {2} was unable to provide metadata about '{1}' expression value '{3}' for {0}.</value>
   </data>

src/Microsoft.AspNet.Mvc.TagHelpers/SelectTagHelper.cs

@@ -14,6 +14,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
     /// <summary>
     /// <see cref="ITagHelper"/> implementation targeting &lt;select&gt; elements with an <c>asp-for</c> attribute.
     /// </summary>
+    [TargetElement("select", Attributes = ForAttributeName)]
     public class SelectTagHelper : TagHelper
     {
         private const string ForAttributeName = "asp-for";
@@ -57,63 +58,47 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            if (For == null)
+            // Note null or empty For.Name is allowed because TemplateInfo.HtmlFieldPrefix may be sufficient.
+            // IHtmlGenerator will enforce name requirements.
+            var metadata = For.Metadata;
+            if (metadata == null)
             {
-                // Regular HTML <select/> element. Just make sure Items wasn't specified.
+                throw new InvalidOperationException(Resources.FormatTagHelpers_NoProvidedMetadata(
-                if (Items != null)
+                    "<select>",
-                {
+                    ForAttributeName,
-                    var message = Resources.FormatSelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified(
+                    nameof(IModelMetadataProvider),
-                        "<select>",
+                    For.Name));
-                        ForAttributeName,
-                        ItemsAttributeName);
-                    throw new InvalidOperationException(message);
-                }
             }
-            else
+
+            // Base allowMultiple on the instance or declared type of the expression to avoid a
+            // "SelectExpressionNotEnumerable" InvalidOperationException during generation.
+            // Metadata.IsCollectionType() is similar but does not take runtime type into account.
+            var realModelType = For.ModelExplorer.ModelType;
+            var allowMultiple = typeof(string) != realModelType && typeof(IEnumerable).IsAssignableFrom(realModelType);
+
+            // Ensure GenerateSelect() _never_ looks anything up in ViewData.
+            var items = Items ?? Enumerable.Empty<SelectListItem>();
+
+            ICollection<string> selectedValues;
+            var tagBuilder = Generator.GenerateSelect(
+                ViewContext,
+                For.ModelExplorer,
+                optionLabel: null,
+                expression: For.Name,
+                selectList: items,
+                allowMultiple: allowMultiple,
+                htmlAttributes: null,
+                selectedValues: out selectedValues);
+
+            if (tagBuilder != null)
             {
-                // Note null or empty For.Name is allowed because TemplateInfo.HtmlFieldPrefix may be sufficient.
+                output.MergeAttributes(tagBuilder);
-                // IHtmlGenerator will enforce name requirements.
+                output.PostContent.Append(tagBuilder.InnerHtml);
-                var metadata = For.Metadata;
-                if (metadata == null)
-                {
-                    throw new InvalidOperationException(Resources.FormatTagHelpers_NoProvidedMetadata(
-                        "<select>",
-                        ForAttributeName,
-                        nameof(IModelMetadataProvider),
-                        For.Name));
-                }
-
-                // Base allowMultiple on the instance or declared type of the expression to avoid a
-                // "SelectExpressionNotEnumerable" InvalidOperationException during generation.
-                // Metadata.IsCollectionType() is similar but does not take runtime type into account.
-                var realModelType = For.ModelExplorer.ModelType;
-                var allowMultiple =
-                        typeof(string) != realModelType && typeof(IEnumerable).IsAssignableFrom(realModelType);
-
-                // Ensure GenerateSelect() _never_ looks anything up in ViewData.
-                var items = Items ?? Enumerable.Empty<SelectListItem>();
-
-                ICollection<string> selectedValues;
-                var tagBuilder = Generator.GenerateSelect(
-                    ViewContext,
-                    For.ModelExplorer,
-                    optionLabel: null,
-                    expression: For.Name,
-                    selectList: items,
-                    allowMultiple: allowMultiple,
-                    htmlAttributes: null,
-                    selectedValues: out selectedValues);
-
-                if (tagBuilder != null)
-                {
-                    output.MergeAttributes(tagBuilder);
-                    output.PostContent.Append(tagBuilder.InnerHtml);
-                }
-
-                // Whether or not (not being highly unlikely) we generate anything, could update contained <option/>
-                // elements. Provide selected values for <option/> tag helpers. They'll run next.
-                ViewContext.FormContext.FormData[SelectedValuesFormDataKey] = selectedValues;
             }
+
+            // Whether or not (not being highly unlikely) we generate anything, could update contained <option/>
+            // elements. Provide selected values for <option/> tag helpers. They'll run next.
+            ViewContext.FormContext.FormData[SelectedValuesFormDataKey] = selectedValues;
         }
     }
 }

src/Microsoft.AspNet.Mvc.TagHelpers/TextAreaTagHelper.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
     /// <summary>
     /// <see cref="ITagHelper"/> implementation targeting &lt;textarea&gt; elements with an <c>asp-for</c> attribute.
     /// </summary>
-    [TargetElement("textarea")]
+    [TargetElement("textarea", Attributes = ForAttributeName)]
     public class TextAreaTagHelper : TagHelper
     {
         private const string ForAttributeName = "asp-for";
@@ -33,23 +33,20 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            if (For != null)
+            var tagBuilder = Generator.GenerateTextArea(
+                ViewContext,
+                For.ModelExplorer,
+                For.Name,
+                rows: 0,
+                columns: 0,
+                htmlAttributes: null);
+
+            if (tagBuilder != null)
             {
-                var tagBuilder = Generator.GenerateTextArea(
+                // Overwrite current Content to ensure expression result round-trips correctly.
-                    ViewContext,
+                output.Content.SetContent(tagBuilder.InnerHtml);
-                    For.ModelExplorer,
-                    For.Name,
-                    rows: 0,
-                    columns: 0,
-                    htmlAttributes: null);
 
-                if (tagBuilder != null)
+                output.MergeAttributes(tagBuilder);
-                {
-                    // Overwrite current Content to ensure expression result round-trips correctly.
-                    output.Content.SetContent(tagBuilder.InnerHtml);
-
-                    output.MergeAttributes(tagBuilder);
-                }
             }
         }
     }

test/Microsoft.AspNet.Mvc.TagHelpers.Test/SelectTagHelperTest.cs

@@ -603,37 +603,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Same(selectedValues, keyValuePair.Value);
         }
 
-        [Fact]
-        public async Task ProcessAsync_Throws_IfForNotBoundButItemsIs()
-        {
-            // Arrange
-            var contextAttributes = new Dictionary<string, object>();
-            var originalAttributes = new Dictionary<string, string>();
-            var expectedTagName = "select";
-            var expectedMessage = "Cannot determine body for <select>. 'asp-items' must be null if 'asp-for' is null.";
-
-            var tagHelperContext = new TagHelperContext(
-                contextAttributes,
-                items: new Dictionary<object, object>(),
-                uniqueId: "test",
-                getChildContentAsync: () =>
-                {
-                    var tagHelperContent = new DefaultTagHelperContent();
-                    tagHelperContent.SetContent("Something");
-                    return Task.FromResult<TagHelperContent>(tagHelperContent);
-                });
-            var output = new TagHelperOutput(expectedTagName, originalAttributes);
-            var tagHelper = new SelectTagHelper
-            {
-                Items = Enumerable.Empty<SelectListItem>(),
-            };
-
-            // Act & Assert
-            var exception = await Assert.ThrowsAsync<InvalidOperationException>(
-                () => tagHelper.ProcessAsync(tagHelperContext, output));
-            Assert.Equal(expectedMessage, exception.Message);
-        }
-
         public class NameAndId
         {
             public NameAndId(string name, string id)

test/Microsoft.AspNet.Mvc.TagHelpers.Test/TextAreaTagHelperTest.cs

@@ -154,67 +154,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal(expectedTagName, output.TagName);
         }
 
-        [Fact]
-        public async Task TagHelper_LeavesOutputUnchanged_IfForNotBound()
-        {
-            // Arrange
-            var expectedAttributes = new Dictionary<string, string>
-            {
-                { "class", "form-control" },
-            };
-            var expectedPreContent = "original pre-content";
-            var expectedContent = "original content";
-            var expectedPostContent = "original post-content";
-            var expectedTagName = "textarea";
-
-            var metadataProvider = new TestModelMetadataProvider();
-            var modelExplorer = metadataProvider
-                .GetModelExplorerForType(typeof(Model), model: null)
-                .GetExplorerForProperty(nameof(Model.Text));
-
-            var modelExpression = new ModelExpression(nameof(Model.Text), modelExplorer);
-            var tagHelper = new TextAreaTagHelper();
-
-            var tagHelperContext = new TagHelperContext(
-                allAttributes: new Dictionary<string, object>(),
-                items: new Dictionary<object, object>(),
-                uniqueId: "test",
-                getChildContentAsync: () =>
-                {
-                    var tagHelperContent = new DefaultTagHelperContent();
-                    tagHelperContent.SetContent("Something");
-                    return Task.FromResult<TagHelperContent>(tagHelperContent);
-                });
-            var output = new TagHelperOutput(expectedTagName, expectedAttributes)
-            {
-                SelfClosing = true,
-            };
-            output.PreContent.SetContent(expectedPreContent);
-            output.Content.SetContent(expectedContent);
-            output.PostContent.SetContent(expectedPostContent);
-
-            var htmlGenerator = new TestableHtmlGenerator(metadataProvider)
-            {
-                ValidationAttributes =
-                {
-                    {  "valid", "from validation attributes" },
-                }
-            };
-            Model model = null;
-            var viewContext = TestableHtmlGenerator.GetViewContext(model, htmlGenerator, metadataProvider);
-            tagHelper.ViewContext = viewContext;
-            tagHelper.Generator = htmlGenerator;
-
-            // Act
-            await tagHelper.ProcessAsync(tagHelperContext, output);
-
-            // Assert
-            Assert.Equal(expectedAttributes, output.Attributes);
-            Assert.Equal(expectedContent, output.Content.GetContent());
-            Assert.True(output.SelfClosing);
-            Assert.Equal(expectedTagName, output.TagName);
-        }
-
         public class NameAndId
         {
             public NameAndId(string name, string id)