Populate TransferUtilityDownloadDirectoryResponse with total objects downloaded

stack-info: PR: #4109, branch: GarrettBeatty/stacked/14

Author: GarrettBeatty

generator/.DevConfigs/c49077d9-90b3-437f-b316-6d8d8833ae73.json

@@ -0,0 +1,11 @@
+{
+  "services": [
+    {
+      "serviceName": "S3",
+      "type": "patch",
+      "changeLogMessages": [
+        "Populate TransferUtilityDownloadDirectoryResponse with total objects downloaded"
+      ]
+    }
+  ]
+}

sdk/src/Services/S3/Custom/Transfer/Internal/_bcl+netstandard/DownloadDirectoryCommand.cs

@@ -65,6 +65,7 @@ public override async Task<TransferUtilityDownloadDirectoryResponse> ExecuteAsyn
 
             SemaphoreSlim asyncThrottler = null;
             CancellationTokenSource internalCts = null;
+            int successfulDownloads = 0;
 
             try
             {
@@ -107,13 +108,25 @@ await asyncThrottler.WaitAsync(cancellationToken)
                     var downloadRequest = ConstructTransferUtilityDownloadRequest(s3o, prefixLength);
                     var command = new DownloadCommand(this._s3Client, downloadRequest);
 
-                    var task = ExecuteCommandAsync(command, internalCts, asyncThrottler);
+                    var task = ExecuteCommandAsync(command, internalCts, asyncThrottler)
+                        .ContinueWith(t => {
+                            if (t.Status == TaskStatus.RanToCompletion)
+                            {
+                                Interlocked.Increment(ref successfulDownloads);
+                            }
+                            return t;
+                        }, TaskScheduler.Default)
+                        .Unwrap();
+                    
                     pendingTasks.Add(task);
                 }
                 await WhenAllOrFirstExceptionAsync(pendingTasks, cancellationToken)
                     .ConfigureAwait(continueOnCapturedContext: false);
 
-                return new TransferUtilityDownloadDirectoryResponse();
+                return new TransferUtilityDownloadDirectoryResponse
+                {
+                    ObjectsDownloaded = successfulDownloads
+                };
             }
             finally
             {

sdk/src/Services/S3/Custom/Transfer/TransferUtilityDownloadDirectoryResponse.cs

@@ -22,5 +22,9 @@ namespace Amazon.S3.Transfer
     /// </summary>
     public class TransferUtilityDownloadDirectoryResponse
     {
+        /// <summary>
+        /// The number of objects that have been downloaded
+        /// </summary>
+        public long ObjectsDownloaded { get; set; }
     }
 }