Add InputTagHelper

- also make `TagHelperOutputExtensions.MergeAttributes()` case-insensitive

nits:
- deliniate attribute names in all resource strings
- update validation messages in TagHelperSample.Web

Author: dougbu

samples/TagHelperSample.Web/Views/Home/Create.cshtml

@@ -37,7 +37,7 @@
             <div class="col-md-10">
                 @* will automatically infer type="date" (reused HTML attribute) and format="{0:d}" (optional bound attribute) *@
                 <input for="DateOfBirth" />
-                <span validation-for="DateOfBirth">How old are you?</span>
+                <span validation-for="DateOfBirth">When were you born?</span>
             </div>
         </div>
         <div class="form-group">

samples/TagHelperSample.Web/Views/Home/Edit.cshtml

@@ -20,7 +20,7 @@
             <label for="DateOfBirth" class="control-label col-md-2" />
             <div class="col-md-10">
                 <input type="date" for="DateOfBirth" format="{0:d}" />
-                <span validation-for="DateOfBirth">How old are you?</span>
+                <span validation-for="DateOfBirth" />
             </div>
         </div>
         <div class="form-group">

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

@@ -118,15 +118,27 @@
     <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
   <data name="AnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified" xml:space="preserve">
-    <value>Cannot determine an {4} for {0}. An {0} with a specified {1} must not have an {2} or {3} attribute.</value>
+    <value>Cannot determine an '{4}' for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
   </data>
   <data name="AnchorTagHelper_CannotOverrideSpecifiedHref" xml:space="preserve">
-    <value>Cannot determine an {8} for {0}. An {0} with a specified {8} must not have attributes starting with {7} or an {1}, {2}, {3}, {4}, {5} or {6} attribute.</value>
+    <value>Cannot determine an '{8}' for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.</value>
+  </data>
+  <data name="InputTagHelper_InvalidExpressionResult" xml:space="preserve">
+    <value>Unexpected '{1}' expression result type '{2}' for {0}. '{1}' must be of type '{3}' if '{4}' is '{5}'.</value>
+  </data>
+  <data name="InputTagHelper_UnableToFormat" xml:space="preserve">
+    <value>Unable to format without a '{1}' expression for {0}. '{2}' must be null if '{1}' is null.</value>
+  </data>
+  <data name="InputTagHelper_ValueRequired" xml:space="preserve">
+    <value>'{1}' must not be null for {0} if '{2}' is '{3}'.</value>
   </data>
   <data name="FormTagHelper_CannotDetermineAction" xml:space="preserve">
-    <value>Cannot determine an {1} for {0}. A {0} with a URL-based {1} must not have attributes starting with {3} or a {2} attribute.</value>
+    <value>Cannot determine an '{1}' for {0}. A {0} with a URL-based '{1}' must not have attributes starting with '{3}' or a '{2}' attribute.</value>
   </data>
   <data name="ValidationSummaryTagHelper_InvalidValidationSummaryValue" xml:space="preserve">
     <value>Cannot parse '{1}' value '{2}' for {0}. Acceptable values are '{3}', '{4}' and '{5}'.</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>
 </root>

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

@@ -89,7 +89,9 @@ public static void MergeAttributes(this TagHelperOutput tagHelperOutput, TagBuil
         {
             foreach (var attribute in tagBuilder.Attributes)
             {
-                if (!tagHelperOutput.Attributes.ContainsKey(attribute.Key))
+                // TODO: Use Attributes.ContainsKey once aspnet/Razor#186 is fixed.
+                if (!tagHelperOutput.Attributes.Any(
+                    item => string.Equals(attribute.Key, item.Key, StringComparison.OrdinalIgnoreCase)))
                 {
                     tagHelperOutput.Attributes.Add(attribute.Key, attribute.Value);
                 }

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

@@ -4,6 +4,7 @@
     "warningsAsErrors": true
   },
   "dependencies": {
+    "Microsoft.AspNet.Mvc.Common": { "version": "6.0.0-*", "type": "build" },
     "Microsoft.AspNet.Mvc.Razor": ""
   },
   "frameworks": {

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

@@ -176,9 +176,9 @@ public async Task ProcessAsync_ThrowsIfHrefConflictsWithBoundAttributes(string p
                 typeof(AnchorTagHelper).GetProperty(propertyName).SetValue(anchorTagHelper, "Home");
             }
 
-            var expectedErrorMessage = "Cannot determine an href for <a>. An <a> with a specified href must not " +
-                                       "have attributes starting with route- or an action, controller, route, " +
-                                       "protocol, host or fragment attribute.";
+            var expectedErrorMessage = "Cannot determine an 'href' for <a>. An <a> with a specified 'href' must not " +
+                                       "have attributes starting with 'route-' or an 'action', 'controller', " +
+                                       "'route', 'protocol', 'host', or 'fragment' attribute.";
 
             // Act & Assert
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(
@@ -202,8 +202,8 @@ public async Task ProcessAsync_ThrowsIfRouteAndActionOrControllerProvided(string
                 "a",
                 attributes: new Dictionary<string, string>(),
                 content: string.Empty);
-            var expectedErrorMessage = "Cannot determine an href for <a>. An <a> with a " +
-                                       "specified route must not have an action or controller attribute.";
+            var expectedErrorMessage = "Cannot determine an 'href' for <a>. An <a> with a " +
+                                       "specified 'route' must not have an 'action' or 'controller' attribute.";
 
             // Act & Assert
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(

src/Microsoft.AspNet.Mvc.TagHelpers/project.json

@@ -301,8 +301,8 @@ public async Task ProcessAsync_ThrowsIfActionIsUrlWithSpecifiedController()
                 Controller = "Home",
                 Method = "POST"
             };
-            var expectedErrorMessage = "Cannot determine an action for <form>. A <form> with a URL-based action " +
-                                       "must not have attributes starting with route- or a controller attribute.";
+            var expectedErrorMessage = "Cannot determine an 'action' for <form>. A <form> with a URL-based 'action' " +
+                                       "must not have attributes starting with 'route-' or a 'controller' attribute.";
             var tagHelperOutput = new TagHelperOutput(
                 "form",
                 attributes: new Dictionary<string, string>(),
@@ -324,8 +324,8 @@ public async Task ProcessAsync_ThrowsIfActionIsUrlWithSpecifiedRoutes()
                 Action = "http://www.contoso.com",
                 Method = "POST"
             };
-            var expectedErrorMessage = "Cannot determine an action for <form>. A <form> with a URL-based action " +
-                                       "must not have attributes starting with route- or a controller attribute.";
+            var expectedErrorMessage = "Cannot determine an 'action' for <form>. A <form> with a URL-based 'action' " +
+                                       "must not have attributes starting with 'route-' or a 'controller' attribute.";
             var tagHelperOutput = new TagHelperOutput(
                 "form",
                 attributes: new Dictionary<string, string>