Modify JsonResult to generate results in UTF8 without BOM by default

Fixes #577

src/Microsoft.AspNet.Mvc.Core/ActionResults/JsonResult.cs

@@ -4,18 +4,19 @@
 using System;
 using System.IO;
 using System.Text;
-using System.Threading.Tasks;
-using Microsoft.AspNet.Http;
 using Newtonsoft.Json;
 
 namespace Microsoft.AspNet.Mvc
 {
     public class JsonResult : ActionResult
     {
+        private const int BufferSize = 1024;
+        private static readonly Encoding UTF8EncodingWithoutBOM 
+            = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false);
         private readonly object _returnValue;
 
         private JsonSerializerSettings _jsonSerializerSettings;
-        private Encoding _encoding = Encoding.UTF8;
+        private Encoding _encoding = UTF8EncodingWithoutBOM;
 
         public JsonResult(object returnValue)
         {
@@ -64,16 +65,15 @@ namespace Microsoft.AspNet.Mvc
 
         public override void ExecuteResult([NotNull] ActionContext context)
         {
-            HttpResponse response = context.HttpContext.Response;
-
-            Stream writeStream = response.Body;
+            var response = context.HttpContext.Response;
+            var writeStream = response.Body;
 
             if (response.ContentType == null)
             {
                 response.ContentType = "application/json";
             }
 
-            using (var writer = new StreamWriter(writeStream, Encoding, 1024, leaveOpen: true))
+            using (var writer = new StreamWriter(writeStream, Encoding, BufferSize, leaveOpen: true))
             {
                 var formatter = new JsonOutputFormatter(SerializerSettings, Indent);
                 formatter.WriteObject(writer, _returnValue);

test/Microsoft.AspNet.Mvc.Core.Test/JsonResultTest.cs

@@ -0,0 +1,75 @@
+// 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.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Http;
+using Microsoft.AspNet.Routing;
+using Moq;
+using Xunit;
+
+
+namespace Microsoft.AspNet.Mvc
+{
+    public class JsonResultTest
+    {
+        private static readonly byte[] _abcdUTF8Bytes 
+            = new byte[] { 123, 34, 102, 111, 111, 34, 58, 34, 97, 98, 99, 100, 34, 125 };
+
+        [Fact]
+        public async Task ExecuteResult_GeneratesResultsWithoutBOMByDefault()
+        {
+            // Arrange
+            var expected = _abcdUTF8Bytes;
+            var memoryStream = new MemoryStream();
+            var response = new Mock<HttpResponse>();
+            response.SetupGet(r => r.Body)
+                   .Returns(memoryStream);
+            var context = new Mock<HttpContext>();
+            context.SetupGet(c => c.Response)
+                   .Returns(response.Object);
+            var actionContext = new ActionContext(context.Object, 
+                                                  Mock.Of<IRouter>(),
+                                                  new Dictionary<string, object>(), 
+                                                  new ActionDescriptor());
+            var result = new JsonResult(new { foo = "abcd" });
+
+            // Act
+            await result.ExecuteResultAsync(actionContext);
+
+            // Assert
+            Assert.Equal(expected, memoryStream.ToArray());
+        }
+
+        [Fact]
+        public async Task ExecuteResult_UsesEncoderIfSpecified()
+        {
+            // Arrange
+            var expected = Enumerable.Concat(Encoding.UTF8.GetPreamble(), _abcdUTF8Bytes);
+            var memoryStream = new MemoryStream();
+            var response = new Mock<HttpResponse>();
+            response.SetupGet(r => r.Body)
+                   .Returns(memoryStream);
+            var context = new Mock<HttpContext>();
+            context.SetupGet(c => c.Response)
+                   .Returns(response.Object);
+            var actionContext = new ActionContext(context.Object,
+                                                  Mock.Of<IRouter>(),
+                                                  new Dictionary<string, object>(),
+                                                  new ActionDescriptor());
+            var result = new JsonResult(new { foo = "abcd" })
+            {
+                Encoding = Encoding.UTF8
+            };
+
+            // Act
+            await result.ExecuteResultAsync(actionContext);
+
+            // Assert
+            Assert.Equal(expected, memoryStream.ToArray());
+        }
+    }
+}