Fix: Do not overwrite content-type header if explicitly set in multipart upload scenario (#3830)

Author: peterrsongg

generator/.DevConfigs/6817cff6-2165-4dbb-ad6e-30d0f34fd3dc.json

@@ -0,0 +1,11 @@
+{
+    "services": [
+        {
+            "serviceName": "S3",
+            "type": "patch",
+            "changeLogMessages": [
+                "Fix: Fixed a bug where Content-Type header was being overwritten in multipart upload scenarios."
+            ]
+        }
+    ]
+}

sdk/src/Services/S3/Custom/Transfer/Internal/MultipartUploadCommand.cs

@@ -354,7 +354,21 @@ private InitiateMultipartUploadRequest ConstructInitiateMultipartUploadRequest(R
             if (this._fileTransporterRequest.Metadata != null && this._fileTransporterRequest.Metadata.Count > 0)
                 initRequest.Metadata = this._fileTransporterRequest.Metadata;
             if (this._fileTransporterRequest.Headers != null && this._fileTransporterRequest.Headers.Count > 0)
-                initRequest.Headers = this._fileTransporterRequest.Headers;
+            {
+                foreach (var headerKey in this._fileTransporterRequest.Headers.Keys)
+                {
+                    // InitiateMultipartUploadRequest already has its content-type header set.
+                    // don't copy the Content-Type if it's set already as to not overwrite the original content-type
+                    if (string.Equals(headerKey, HeaderKeys.ContentTypeHeader) && this._fileTransporterRequest.IsSetContentType())
+                    {
+                        continue;
+                    }
+                    else
+                    {
+                        initRequest.Headers[headerKey] = this._fileTransporterRequest.Headers[headerKey];
+                    }
+                }
+            }
 
             return initRequest;
         }

sdk/test/Services/S3/IntegrationTests/TransferUtilityTests.cs

@@ -11,6 +11,7 @@
 using Amazon.S3.Util;
 using AWSSDK_DotNet.IntegrationTests.Utils;
 using Amazon.Util;
+using System.Net.Mime;
 
 namespace AWSSDK_DotNet.IntegrationTests.Tests.S3
 {
@@ -1011,6 +1012,32 @@ public void TestZeroLengthDownloadToNonExistingPath()
             Assert.IsTrue(File.Exists(filePath));
         }
 
+        [TestMethod]
+        [TestCategory("S3")]
+        public void TestMultipartUploadWithSetContentTypeNotOverwritten()
+        {
+            // 20 MB stream
+            var fileName = UtilityMethods.GenerateName(@"SetContentType");
+            var path = Path.Combine(BasePath, fileName);
+            var fileSize = 20 * MEG_SIZE;
+            UtilityMethods.GenerateFile(path, 20 * MEG_SIZE);
+            var transferUtilityRequest = new TransferUtilityUploadRequest
+            {
+                BucketName = bucketName,
+                FilePath = path,
+                Key = "test-content-type",
+                ContentType = MediaTypeNames.Text.Plain,
+                Headers =
+                {
+                    ContentEncoding = "gzip",
+                },
+            };
+            var tu = new TransferUtility(Client);
+            tu.Upload(transferUtilityRequest);
+            var downloadPath = path + ".download";
+            var metadata = Client.GetObjectMetadata(new GetObjectMetadataRequest { BucketName = bucketName, Key = "test-content-type" });
+            Assert.IsTrue(metadata.Headers.ContentType.Equals(MediaTypeNames.Text.Plain));
+        }
 #if ASYNC_AWAIT
 
         [TestMethod]