Implement StreamResponse (#110)

Implements the `StreamResponse` class that provides direct access to the
response content stream.

Author: flobernd

src/Elastic.Transport/Components/Pipeline/DefaultResponseBuilder.cs

@@ -12,8 +12,10 @@
 using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
+
 using Elastic.Transport.Diagnostics;
 using Elastic.Transport.Extensions;
+
 using static Elastic.Transport.ResponseBuilderDefaults;
 
 namespace Elastic.Transport;
@@ -26,7 +28,6 @@ internal static class ResponseBuilderDefaults
 	{
 		typeof(StringResponse), typeof(BytesResponse), typeof(VoidResponse), typeof(DynamicResponse)
 	};
-
 }
 
 /// <summary>
@@ -225,7 +226,7 @@ private async ValueTask<TResponse> SetBodyCoreAsync<TResponse>(bool isAsync,
 
 		using (responseStream)
 		{
-			if (SetSpecialTypes<TResponse>(mimeType, bytes, requestData.MemoryStreamFactory, out var r)) return r;
+			if (SetSpecialTypes<TResponse>(mimeType, bytes, responseStream, requestData.MemoryStreamFactory, out var r)) return r;
 
 			if (details.HttpStatusCode.HasValue &&
 				requestData.SkipDeserializationForStatusCodes.Contains(details.HttpStatusCode.Value))
@@ -288,7 +289,7 @@ private async ValueTask<TResponse> SetBodyCoreAsync<TResponse>(bool isAsync,
 		}
 	}
 
-	private static bool SetSpecialTypes<TResponse>(string mimeType, byte[] bytes,
+	private static bool SetSpecialTypes<TResponse>(string mimeType, byte[] bytes, Stream responseStream,
 		MemoryStreamFactory memoryStreamFactory, out TResponse cs)
 		where TResponse : TransportResponse, new()
 	{
@@ -298,6 +299,8 @@ private static bool SetSpecialTypes<TResponse>(string mimeType, byte[] bytes,
 
 		if (responseType == typeof(StringResponse))
 			cs = new StringResponse(bytes.Utf8String()) as TResponse;
+		else if (responseType == typeof(StreamResponse))
+			cs = new StreamResponse(responseStream, mimeType) as TResponse;
 		else if (responseType == typeof(BytesResponse))
 			cs = new BytesResponse(bytes) as TResponse;
 		else if (responseType == typeof(VoidResponse))

src/Elastic.Transport/Components/TransportClient/HttpRequestInvoker.cs

@@ -118,6 +118,7 @@ private async ValueTask<TResponse> RequestCoreAsync<TResponse>(bool isAsync, Req
 					responseMessage = client.SendAsync(requestMessage, HttpCompletionOption.ResponseHeadersRead, cancellationToken).GetAwaiter().GetResult();
 #endif
 
+				receive = responseMessage;
 				statusCode = (int)responseMessage.StatusCode;
 			}
 
@@ -152,8 +153,11 @@ private async ValueTask<TResponse> RequestCoreAsync<TResponse>(bool isAsync, Req
 		{
 			ex = e;
 		}
-		using (receive)
-		using (responseStream ??= Stream.Null)
+
+		var isStreamResponse = typeof(TResponse) == typeof(StreamResponse);
+
+		using (isStreamResponse ? DiagnosticSources.SingletonDisposable : receive)
+		using (isStreamResponse ? Stream.Null : responseStream ??= Stream.Null)
 		{
 			TResponse response;
 
@@ -165,6 +169,10 @@ private async ValueTask<TResponse> RequestCoreAsync<TResponse>(bool isAsync, Req
 				response = requestData.ConnectionSettings.ProductRegistration.ResponseBuilder.ToResponse<TResponse>
 						(requestData, ex, statusCode, responseHeaders, responseStream, mimeType, contentLength, threadPoolStats, tcpStats);
 
+			// Defer disposal of the response message
+			if (response is StreamResponse sr)
+				sr.Finalizer = () => receive.Dispose();
+
 			if (!OpenTelemetry.CurrentSpanIsElasticTransportOwnedAndHasListeners || (!(Activity.Current?.IsAllDataRequested ?? false)))
 				return response;
 

src/Elastic.Transport/Responses/Special/StreamResponse.cs

@@ -0,0 +1,40 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System;
+using System.IO;
+
+namespace Elastic.Transport;
+
+/// <summary>
+/// A response that exposes the response <see cref="TransportResponse{T}.Body"/> as <see cref="Stream"/>.
+/// <para>
+///		Must be disposed after use.
+/// </para>
+/// </summary>
+public sealed class StreamResponse :
+	TransportResponse<Stream>,
+	IDisposable
+{
+	internal Action? Finalizer { get; set; }
+
+	/// <summary>
+	/// The MIME type of the response, if present.
+	/// </summary>
+	public string MimeType { get; }
+
+	/// <inheritdoc cref="StreamResponse"/>
+	public StreamResponse(Stream body, string? mimeType)
+	{
+		Body = body;
+		MimeType = mimeType ?? string.Empty;
+	}
+
+	/// <inheritdoc cref="IDisposable.Dispose"/>
+	public void Dispose()
+	{
+		Body.Dispose();
+		Finalizer?.Invoke();
+	}
+}