fix #1589 premature disposal of request state when using async which caused the end result not being traced

Author: Mpdreamz

Diff for: src/Elasticsearch.Net/Connection/RequestState/TransportRequestState.cs

@@ -205,12 +205,15 @@ public void SetResult(ElasticsearchResponse<T> result)
 			this._result = result;
 
 		}
-
+			
+		public bool IsDisposed { get; private set; }
 		public void Dispose()
 		{
-			if (!_traceEnabled || this._result == null)
+			if (IsDisposed || !_traceEnabled || this._result == null)
 				return;
 
+			this.IsDisposed = true;
+
             string traceMessage = string.Format(
                 "NEST end:{0} {1} {2} ({3}):\r\n{4}"
                 , this._requestId

Diff for: src/Elasticsearch.Net/Connection/Transport.cs

@@ -346,20 +346,18 @@ public ElasticsearchResponse<T> DoRequest<T>(string method, string path, object
 
 		public Task<ElasticsearchResponse<T>> DoRequestAsync<T>(string method, string path, object data = null, IRequestParameters requestParameters = null)
 		{
-			using (var requestState = new TransportRequestState<T>(this.Settings, requestParameters, method, path))
-			{
-				return this._requestHandlerAsync.RequestAsync(requestState, data)
-					.ContinueWith<ElasticsearchResponse<T>>(t =>
+			var requestState = new TransportRequestState<T>(this.Settings, requestParameters, method, path);
+			return this._requestHandlerAsync.RequestAsync(requestState, data)
+				.ContinueWith<ElasticsearchResponse<T>>(t =>
+				{
+					requestState.Dispose();
+					if (t.IsFaulted && t.Exception != null)
 					{
-						if (t.IsFaulted && t.Exception != null)
-						{
-							t.Exception.Flatten().InnerException.RethrowKeepingStackTrace();
-							return null; //won't be hit
+						t.Exception.Flatten().InnerException.RethrowKeepingStackTrace();
+						return null; //won't be hit
 						}
-
-						return t.Result;
-					});
-			}
+					return t.Result;
+				});
 		}
 	}
 }

Diff for: src/Tests/Nest.Tests.Unit/Settings/UseTraceWriterTests.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Text;
+using System.Threading.Tasks;
 using Elasticsearch.Net;
 using Elasticsearch.Net.Connection;
 using FluentAssertions;
@@ -29,5 +30,24 @@ public void EnableTraceShouldWriteToPassedTextWriter()
 			lines[0].Should().StartWith("NEST start:");
 			lines[1].Should().StartWith("NEST end:");
 		}
+
+		[Test]
+		public async Task EnableTraceShouldWriteToPassedTextWriterAsync()
+		{
+			var stringBuilder = new StringBuilder();
+			using (var writer = new StringWriter(stringBuilder))
+			{
+				var settings = new ConnectionSettings(UnitTestDefaults.Uri, UnitTestDefaults.DefaultIndex)
+					.EnableTrace(true, writer);
+				var connection = new InMemoryConnection(settings);
+				var client = new ElasticClient(settings, connection);
+
+				var r = await client.ClusterHealthAsync(h => h.Level(Level.Cluster));
+			}
+
+			var lines = stringBuilder.ToString().Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
+			lines[0].Should().StartWith("NEST start:");
+			lines[1].Should().StartWith("NEST end:");
+		}
 	}
 }