Implement StreamOutputFormatter

Include Functional tests and unit tests

Resolves #1653

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

@@ -69,6 +69,14 @@ namespace Microsoft.AspNet.Mvc
         public virtual IOutputFormatter SelectFormatter(OutputFormatterContext formatterContext,
                                                        IEnumerable<IOutputFormatter> formatters)
         {
+            if (ContentTypes.Count == 1)
+            {
+                // There is only one content type specified so we can skip looking at the accept headers.
+                return SelectFormatterUsingAnyAcceptableContentType(formatterContext,
+                                                                    formatters,
+                                                                    ContentTypes);
+            }
+
             var incomingAcceptHeaderMediaTypes = formatterContext.ActionContext.HttpContext.Request.GetTypedHeaders().Accept ??
                                                     new MediaTypeHeaderValue[] { };
 
@@ -143,14 +151,6 @@ namespace Microsoft.AspNet.Mvc
                     }
                 }
             }
-            else if (ContentTypes.Count == 1)
-            {
-                // There is only one value that can be supported.
-                selectedFormatter = SelectFormatterUsingAnyAcceptableContentType(
-                                                                            formatterContext,
-                                                                            formatters,
-                                                                            ContentTypes);
-            }
             else
             {
                 if (respectAcceptHeader)

src/Microsoft.AspNet.Mvc.Core/Formatters/StreamOutputFormatter.cs

@@ -0,0 +1,72 @@
+// 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 System.IO;
+using System.Threading.Tasks;
+using Microsoft.Net.Http.Headers;
+
+namespace Microsoft.AspNet.Mvc
+{
+    /// <summary>
+    /// Always copies the stream to the response, regardless of requested content type.
+    /// </summary>
+    public class StreamOutputFormatter : IOutputFormatter
+    {
+        /// <summary>
+        /// Echos the <paramref name="contentType"/> if the <paramref name="runtimeType"/> implements 
+        /// <see cref="Stream"/> and <paramref name="contentType"/> is not <c>null</c>.
+        /// </summary>
+        /// <param name="declaredType">The declared type for which the supported content types are desired.</param>
+        /// <param name="runtimeType">The runtime type for which the supported content types are desired.</param>
+        /// <param name="contentType">
+        /// The content type for which the supported content types are desired, or <c>null</c> if any content
+        /// type can be used.
+        /// </param>
+        /// <returns>Content types which are supported by this formatter.</returns>
+        public IReadOnlyList<MediaTypeHeaderValue> GetSupportedContentTypes(
+            Type declaredType,
+            Type runtimeType,
+            MediaTypeHeaderValue contentType)
+        {
+            if (contentType != null &&
+                runtimeType != null &&
+                typeof(Stream).IsAssignableFrom(runtimeType))
+            {
+                return new[] { contentType };
+            }
+
+            return null;
+        }
+
+        /// <inheritdoc />
+        public bool CanWriteResult([NotNull] OutputFormatterContext context, MediaTypeHeaderValue contentType)
+        {
+            // Ignore the passed in content type, if the object is a Stream.
+            if (context.Object is Stream)
+            {
+                context.SelectedContentType = contentType;
+                return true;
+            }
+
+            return false;
+        }
+
+        /// <inheritdoc />
+        public async Task WriteAsync([NotNull] OutputFormatterContext context)
+        {
+            using (var valueAsStream = ((Stream)context.Object))
+            {
+                var response = context.ActionContext.HttpContext.Response;
+
+                if (context.SelectedContentType != null)
+                {
+                    response.ContentType = context.SelectedContentType.ToString();
+                }
+
+                await valueAsStream.CopyToAsync(response.Body);
+            }
+        }
+    }
+}

src/Microsoft.AspNet.Mvc/MvcOptionsSetup.cs

@@ -44,6 +44,7 @@ namespace Microsoft.AspNet.Mvc
             // Set up default output formatters.
             options.OutputFormatters.Add(new HttpNoContentOutputFormatter());
             options.OutputFormatters.Add(new StringOutputFormatter());
+            options.OutputFormatters.Add(new StreamOutputFormatter());
             options.OutputFormatters.Add(new JsonOutputFormatter());
 
             // Set up default mapping for json extensions to content type

test/Microsoft.AspNet.Mvc.Core.Test/Formatters/StreamOutputFormatterTest.cs

@@ -0,0 +1,89 @@
+// 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.IO;
+using Microsoft.Net.Http.Headers;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc
+{
+    public class StreamOutputFormatterTest
+    {
+        [Theory]
+        [InlineData(typeof(Stream), typeof(FileStream), "text/plain", "text/plain")]
+        [InlineData(typeof(object), typeof(FileStream), "text/plain", "text/plain")]
+        [InlineData(typeof(object), typeof(MemoryStream), "text/plain", "text/plain")]
+        [InlineData(typeof(object), typeof(object), "text/plain", null)]
+        [InlineData(typeof(object), typeof(string), "text/plain", null)]
+        [InlineData(typeof(object), null, "text/plain", null)]
+        [InlineData(typeof(IActionResult), null, "text/plain", null)]
+        [InlineData(typeof(IActionResult), typeof(IActionResult), "text/plain", null)]
+        public void GetSupportedContentTypes_ReturnsAppropriateValues(Type declaredType,
+                                                                      Type runtimeType,
+                                                                      string contentType,
+                                                                      string expected)
+        {
+            // Arrange
+            var formatter = new StreamOutputFormatter();
+            var contentTypeHeader = contentType == null ? null : new MediaTypeHeaderValue(contentType);
+
+            // Act
+            var contentTypes = formatter.GetSupportedContentTypes(declaredType, runtimeType, contentTypeHeader);
+
+            // Assert
+            if (expected == null)
+            {
+                Assert.Null(contentTypes);
+            }
+            else
+            {
+                Assert.Equal(1, contentTypes.Count);
+                Assert.Equal(expected, contentTypes[0].ToString());
+            }
+        }
+
+        [Theory]
+        [InlineData(typeof(object))]
+        [InlineData(typeof(SimplePOCO))]
+        [InlineData(null)]
+        public void CanWriteResult_OnlyActsOnStreams(Type type)
+        {
+            // Arrange
+            var formatter = new StreamOutputFormatter();
+            var context = new OutputFormatterContext();
+            var contentType = new MediaTypeHeaderValue("text/plain");
+
+            context.Object = type != null ? Activator.CreateInstance(type) : null;
+
+            // Act
+            var result = formatter.CanWriteResult(context, contentType);
+
+            // Assert
+            Assert.False(result);
+            Assert.Null(context.SelectedContentType);
+        }
+
+        [Fact]
+        public void CanWriteResult_SetsContentType()
+        {
+            // Arrange
+            var formatter = new StreamOutputFormatter();
+            var contentType = new MediaTypeHeaderValue("text/plain");
+            var context = new OutputFormatterContext();
+            context.Object = new MemoryStream();
+
+            // Act
+            var result = formatter.CanWriteResult(context, contentType);
+
+            // Assert
+            Assert.True(result);
+            Assert.Same(contentType, context.SelectedContentType);
+        }
+
+        private class SimplePOCO
+        {
+            public int Id { get; set; }
+        }
+    }
+}

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

@@ -0,0 +1,40 @@
+// 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.Threading.Tasks;
+using FormatterWebSite;
+using Microsoft.AspNet.Builder;
+using Microsoft.AspNet.TestHost;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.FunctionalTests
+{
+    public class StreamOutputFormatterTest
+    {
+        private readonly IServiceProvider _provider = TestHelper.CreateServices(nameof(FormatterWebSite));
+        private readonly Action<IApplicationBuilder> _app = new Startup().Configure;
+
+        [Theory]
+        [InlineData("SimpleMemoryStream", null)]
+        [InlineData("MemoryStreamWithContentType", "text/html")]
+        [InlineData("MemoryStreamWithContentTypeFromProduces", "text/plain")]
+        [InlineData("MemoryStreamWithContentTypeFromProducesWithMultipleValues", "text/html")]
+        [InlineData("MemoryStreamOverridesContentTypeWithProduces", "text/plain")]
+        public async Task StreamOutputFormatter_ReturnsAppropriateContentAndContentType(string actionName, string contentType)
+        {
+            // Arrange
+            var server = TestServer.Create(_provider, _app);
+            var client = server.CreateClient();
+
+            // Act
+            var response = await client.GetAsync("http://localhost/Stream/" + actionName);
+            var body = await response.Content.ReadAsStringAsync();
+
+            // Assert
+            Assert.Equal(contentType, response.Content.Headers.ContentType?.ToString());
+
+            Assert.Equal("Sample text from a stream", body);
+        }
+    }
+}

test/Microsoft.AspNet.Mvc.Test/MvcOptionsSetupTest.cs

@@ -10,7 +10,7 @@ using Xunit;
 
 namespace Microsoft.AspNet.Mvc
 {
-    public class MvcOptionSetupTest
+    public class MvcOptionsSetupTest
     {
         [Fact]
         public void Setup_SetsUpViewEngines()
@@ -83,10 +83,11 @@ namespace Microsoft.AspNet.Mvc
             setup.Configure(mvcOptions);
 
             // Assert
-            Assert.Equal(3, mvcOptions.OutputFormatters.Count);
+            Assert.Equal(4, mvcOptions.OutputFormatters.Count);
             Assert.IsType<HttpNoContentOutputFormatter>(mvcOptions.OutputFormatters[0].Instance);
             Assert.IsType<StringOutputFormatter>(mvcOptions.OutputFormatters[1].Instance);
-            Assert.IsType<JsonOutputFormatter>(mvcOptions.OutputFormatters[2].Instance);
+            Assert.IsType<StreamOutputFormatter>(mvcOptions.OutputFormatters[2].Instance);
+            Assert.IsType<JsonOutputFormatter>(mvcOptions.OutputFormatters[3].Instance);
         }
 
         [Fact]

test/WebSites/FormatterWebSite/Controllers/StreamController.cs

@@ -0,0 +1,60 @@
+// 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.IO;
+using Microsoft.AspNet.Mvc;
+
+namespace FormatterWebSite
+{
+    public class StreamController : Controller
+    {
+        [HttpGet]
+        public Stream SimpleMemoryStream()
+        {
+            return CreateDefaultStream();
+        }
+
+        [HttpGet]
+        public Stream MemoryStreamWithContentType()
+        {
+            Response.ContentType = "text/html";
+            return CreateDefaultStream();
+        }
+
+        [HttpGet]
+        [Produces("text/plain")]
+        public Stream MemoryStreamWithContentTypeFromProduces()
+        {
+            return CreateDefaultStream();
+        }
+
+        [HttpGet]
+        [Produces("text/html", "text/plain")]
+        public Stream MemoryStreamWithContentTypeFromProducesWithMultipleValues()
+        {
+            return CreateDefaultStream();
+        }
+
+        [HttpGet]
+        [Produces("text/plain")]
+        public Stream MemoryStreamOverridesContentTypeWithProduces()
+        {
+            // Produces will set a ContentType on the implicit ObjectResult and
+            // ContentType on response are overriden by content types from ObjectResult.
+            Response.ContentType = "text/html";
+
+            return CreateDefaultStream();
+        }
+
+        private static Stream CreateDefaultStream()
+        {
+            var stream = new MemoryStream();
+            var writer = new StreamWriter(stream);
+            writer.Write("Sample text from a stream");
+            writer.Flush();
+            stream.Seek(0, SeekOrigin.Begin);
+
+            return stream;
+        }
+    }
+}