Compression header handling

src/Microsoft.Graph.Core/Requests/Middleware/CompressionHandler.cs

@@ -9,6 +9,7 @@ namespace Microsoft.Graph
     using System.Threading.Tasks;
     using System.Net.Http.Headers;
     using System.IO.Compression;
+    using System.Collections.Generic;
 
     /// <summary>
     /// A <see cref="DelegatingHandler"/> implementation that handles compression.
@@ -53,7 +54,13 @@ protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage
             // Decompress response content when Content-Encoding: gzip header is present.
             if (ShouldDecompressContent(response))
             {
-                response.Content = new StreamContent(new GZipStream(await response.Content.ReadAsStreamAsync(), CompressionMode.Decompress));
+                StreamContent streamContent = new StreamContent(new GZipStream(await response.Content.ReadAsStreamAsync(), CompressionMode.Decompress));
+                // Copy Content Headers to the destination stream content
+                foreach (var httpContentHeader in response.Content.Headers)
+                {
+                    streamContent.Headers.TryAddWithoutValidation(httpContentHeader.Key, httpContentHeader.Value);
+                }
+                response.Content = streamContent;
             }
 
             return response;

tests/Microsoft.Graph.DotnetCore.Core.Test/Requests/Middleware/CompressionHandlerTests.cs

@@ -12,6 +12,9 @@ namespace Microsoft.Graph.DotnetCore.Core.Test.Requests.Middleware
     using System.Threading.Tasks;
     using System.Threading;
     using System.Net.Http.Headers;
+    using System.Linq;
+    using System.Collections.Generic;
+    using Xunit.Abstractions;
 
     public class CompressionHandlerTests : IDisposable
     {
@@ -94,5 +97,55 @@ public async Task CompressionHandler_should_not_decompress_response_without_cont
             Assert.Same(httpRequestMessage, compressedResponse.RequestMessage);
             Assert.NotEqual(stringToCompress, responseContentString);
         }
+
+        /// <summary>
+        /// Compression Handler should keep content headers after decompression
+        /// </summary>
+        /// <returns></returns>
+        [Fact]
+        public async Task CompressionHandler_should_keep_headers_after_decompression()
+        {
+            HttpRequestMessage httpRequestMessage = new HttpRequestMessage(HttpMethod.Get, "http://example.org/foo");
+
+            string stringToCompress = "Microsoft Graph";
+            StringContent stringContent = new StringContent(stringToCompress);
+            stringContent.Headers.ContentType = new MediaTypeHeaderValue(CoreConstants.MimeTypeNames.Application.Json);
+
+            HttpResponseMessage httpResponse = new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new MockCompressedContent(stringContent)
+            };
+            httpResponse.Content.Headers.ContentEncoding.Add(CoreConstants.Encoding.GZip);
+            httpResponse.Headers.CacheControl = new CacheControlHeaderValue { Private = true };
+            // Examples of Custom Headers returned by Microsoft Graph
+            httpResponse.Headers.Add(CoreConstants.Headers.ClientRequestId, Guid.NewGuid().ToString());
+            httpResponse.Headers.Add("request-id", Guid.NewGuid().ToString());
+            httpResponse.Headers.Add("OData-Version", "4.0");
+
+            this.testHttpMessageHandler.SetHttpResponse(httpResponse);
+
+            HttpResponseMessage compressedResponse = await this.invoker.SendAsync(httpRequestMessage, new CancellationToken());
+            string responseContentString = await compressedResponse.Content.ReadAsStringAsync();
+
+            // Ensure that headers in the compressedResponse are the same as in the original, expected response.
+            Assert.NotEmpty(compressedResponse.Headers);
+            Assert.NotEmpty(compressedResponse.Content.Headers);
+            Assert.Equal(httpResponse.Headers, compressedResponse.Headers, new HttpHeaderComparer());
+            Assert.Equal(httpResponse.Content.Headers, compressedResponse.Content.Headers, new HttpHeaderComparer());
+        }
+
+        internal class HttpHeaderComparer : IEqualityComparer<KeyValuePair<string, IEnumerable<string>>>
+        {
+            public bool Equals(KeyValuePair<string, IEnumerable<string>> x, KeyValuePair<string, IEnumerable<string>> y)
+            {
+                // For each key, the collection of header values should be equal.
+                return x.Key == y.Key && x.Value.SequenceEqual(y.Value);
+            }
+
+            public int GetHashCode(KeyValuePair<string, IEnumerable<string>> obj)
+            {
+                return obj.Key.GetHashCode();
+            }
+        }
     }
 }