Fix for #1681 - Model state errors are wrong with attributes like [FromHeader]

The issue here is that a model state error is added with the model name
'doubled'. This is on a fairly obscure code path and the code dates back
to the original WSR git checkin of webapi. There are no wsr tests that
verify this behavior.

The cause here is that our 'greedy' model binders (like
FromHeaderModelBinder) return 'true' whether or not they successfully
found a model, because they don't want other model binders to run.

This also has an effect on the validation system. That means that
validators will run and attempt to validate the model (which may be null).
That's that rare case where we get to this code path.

src/Microsoft.AspNet.Mvc.ModelBinding/Validation/ModelValidationNode.cs

@@ -190,11 +190,9 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             // If the Model at the current node is null and there is no parent, we cannot validate, and the
             // DataAnnotationsModelValidator will throw. So we intercept here to provide a catch-all value-required
             // validation error
-            var modelStateKey = ModelBindingHelper.CreatePropertyModelName(ModelStateKey,
-                                                                           ModelMetadata.GetDisplayName());
             if (parentNode == null && ModelMetadata.Model == null)
             {
-                modelState.TryAddModelError(modelStateKey, Resources.Validation_ValueNotFound);
+                modelState.TryAddModelError(ModelStateKey, Resources.Validation_ValueNotFound);
                 return;
             }
 

test/Microsoft.AspNet.Mvc.FunctionalTests/ModelBindingFromHeaderTest.cs

@@ -96,10 +96,9 @@ namespace Microsoft.AspNet.Mvc.FunctionalTests
 
             Assert.Null(result.HeaderValue);
             Assert.Null(result.HeaderValues);
-
-            // This is a bug - the model state error key is wrong here.
+            
             var error = Assert.Single(result.ModelStateErrors);
-            Assert.Equal("transactionId.transactionId", error);
+            Assert.Equal("transactionId", error);
         }
 
         // The action that this test hits will echo back the model-bound values

test/Microsoft.AspNet.Mvc.ModelBinding.Test/Validation/ModelValidationNodeTest.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 #if ASPNET50
+using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.Linq;
@@ -245,6 +246,27 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             Assert.Empty(log);
         }
 
+        [Fact]
+        public void Validate_ValidatesIfModelIsNull()
+        {
+            // Arrange
+            var modelMetadata = GetModelMetadata(typeof(ValidateAllPropertiesModel));
+            var node = new ModelValidationNode(modelMetadata, "theKey");
+
+            var context = CreateContext(modelMetadata);
+
+            // Act
+            node.Validate(context);
+
+            // Assert
+            var modelState = Assert.Single(context.ModelState);
+            Assert.Equal("theKey", modelState.Key);
+            Assert.Equal(ModelValidationState.Invalid, modelState.Value.ValidationState);
+
+            var error = Assert.Single(modelState.Value.Errors);
+            Assert.Equal("A value is required but was not present in the request.", error.ErrorMessage);
+        }
+
         [Fact]
         [ReplaceCulture]
         public void Validate_ValidateAllProperties_AddsValidationErrors()
@@ -321,6 +343,11 @@ namespace Microsoft.AspNet.Mvc.ModelBinding
             return new DataAnnotationsModelMetadataProvider().GetMetadataForType(() => o, o.GetType());
         }
 
+        private static ModelMetadata GetModelMetadata(Type type)
+        {
+            return new DataAnnotationsModelMetadataProvider().GetMetadataForType(modelAccessor: null, modelType: type);
+        }
+
         private static ModelValidationContext CreateContext(ModelMetadata metadata = null)
         {
             var providers = new IModelValidatorProvider[]