ensure RequestDataContent can handle null postdata again

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

@@ -160,7 +160,7 @@ MemoryStreamFactory memoryStreamFactory
 	public ITransportConfiguration ConnectionSettings { get; }
 	public CustomResponseBuilder? CustomResponseBuilder { get; }
 	public HeadersList? ResponseHeadersToParse { get; }
-	public NameValueCollection Headers { get; }
+	public NameValueCollection? Headers { get; }
 	public bool DisableDirectStreaming { get; }
 	public bool ParseAllHeaders { get; }
 	public bool DisableAutomaticProxyDetection { get; }
@@ -186,7 +186,7 @@ MemoryStreamFactory memoryStreamFactory
 
 	public TimeSpan DnsRefreshTimeout { get; }
 
-	public MetaHeaderProvider MetaHeaderProvider { get; }
+	public MetaHeaderProvider? MetaHeaderProvider { get; }
 
 	public IReadOnlyDictionary<string, string> RequestMetaData { get; }
 

src/Elastic.Transport/Components/TransportClient/Content/RequestDataContent.cs

@@ -29,12 +29,12 @@ namespace Elastic.Transport;
 internal sealed class RequestDataContent : HttpContent
 {
 	private readonly RequestData _requestData;
-	private readonly PostData _postData;
+	private readonly PostData? _postData;
 
-	private readonly Func<RequestData, PostData, CompleteTaskOnCloseStream, RequestDataContent, TransportContext, CancellationToken, Task>
+	private readonly Func<RequestData, PostData?, CompleteTaskOnCloseStream, RequestDataContent, TransportContext, CancellationToken, Task>
 		_onStreamAvailableAsync;
 
-	private readonly Action<RequestData, PostData, CompleteTaskOnCloseStream, RequestDataContent, TransportContext> _onStreamAvailable;
+	private readonly Action<RequestData, PostData?, CompleteTaskOnCloseStream, RequestDataContent, TransportContext> _onStreamAvailable;
 	private readonly CancellationToken _token;
 
 	/// <summary> Constructor used in synchronous paths. </summary>
@@ -53,8 +53,13 @@ public RequestDataContent(RequestData requestData, PostData postData)
 		_onStreamAvailableAsync = OnStreamAvailableAsync;
 	}
 
-	private static void OnStreamAvailable(RequestData data, PostData postData, Stream stream, HttpContent content, TransportContext context)
+	private static void OnStreamAvailable(RequestData data, PostData? postData, Stream stream, HttpContent content, TransportContext context)
 	{
+		if (postData == null)
+		{
+			stream.Dispose();
+			return;
+		}
 		if (data.HttpCompression) stream = new GZipStream(stream, CompressionMode.Compress, false);
 
 		using (stream) postData.Write(stream, data.ConnectionSettings, data.DisableDirectStreaming);
@@ -75,8 +80,17 @@ public RequestDataContent(RequestData requestData, CancellationToken token)
 		_onStreamAvailableAsync = OnStreamAvailableAsync;
 	}
 
-	private static async Task OnStreamAvailableAsync(RequestData data, PostData postData, Stream stream, HttpContent content, TransportContext context, CancellationToken ctx = default)
+	private static async Task OnStreamAvailableAsync(RequestData data, PostData? postData, Stream stream, HttpContent content, TransportContext context, CancellationToken ctx = default)
 	{
+		if (postData == null)
+		{
+#if NET6_0_OR_GREATER
+			await stream.DisposeAsync().ConfigureAwait(false);
+#else
+			stream.Dispose();
+#endif
+			return;
+		}
 		if (data.HttpCompression) stream = new GZipStream(stream, CompressionMode.Compress, false);
 
 #if NET6_0_OR_GREATER

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

@@ -193,7 +193,7 @@ private async ValueTask<TResponse> RequestCoreAsync<TResponse>(bool isAsync, End
 		{
 			// if there's an exception, ensure we always release the stream and response so that the connection is freed.
 			responseStream.Dispose();
-			receivedResponse.Dispose(); 
+			receivedResponse.Dispose();
 			throw;
 		}
 	}
@@ -343,7 +343,7 @@ internal HttpRequestMessage CreateHttpRequestMessage(Endpoint endpoint, RequestD
 	internal void SetAuthenticationIfNeeded(Endpoint endpoint, RequestData requestData, HttpRequestMessage requestMessage)
 	{
 		//If user manually specifies an Authorization Header give it preference
-		if (requestData.Headers.HasKeys() && requestData.Headers.AllKeys.Contains("Authorization"))
+		if (requestData.Headers != null && requestData.Headers.HasKeys() && requestData.Headers.AllKeys.Contains("Authorization"))
 		{
 			var header = AuthenticationHeaderValue.Parse(requestData.Headers["Authorization"]);
 			requestMessage.Headers.Authorization = header;

src/Elastic.Transport/Configuration/ITransportConfiguration.cs

@@ -195,7 +195,7 @@ public interface ITransportConfiguration : IRequestConfiguration, IDisposable
 	/// <summary>
 	/// Produces the client meta header for a request.
 	/// </summary>
-	MetaHeaderProvider MetaHeaderProvider { get; }
+	MetaHeaderProvider? MetaHeaderProvider { get; }
 
 	/// <summary>
 	/// Disables the meta header which is included on all requests by default. This header contains lightweight information

src/Elastic.Transport/DistributedTransport.cs

@@ -307,7 +307,9 @@ private static void ThrowUnexpectedTransportException<TResponse>(Exception kille
 	) where TResponse : TransportResponse, new() =>
 		throw new UnexpectedTransportException(killerException, seenExceptions)
 		{
-			Endpoint = endpoint, ApiCallDetails = response?.ApiCallDetails, AuditTrail = pipeline.AuditTrail
+			Endpoint = endpoint,
+			ApiCallDetails = response?.ApiCallDetails,
+			AuditTrail = pipeline.AuditTrail
 		};
 
 	private static void HandlePipelineException<TResponse>(

tests/Elastic.Transport.IntegrationTests/Http/StreamResponseTests.cs

@@ -106,11 +106,9 @@ public async Task WhenNoContent_MemoryStreamShouldBeDisposed()
 
 		// We expect one for sending the request payload, but as the response is 204, we shouldn't
 		// see other memory streams being created for the response.
-		memoryStreamFactory.Created.Count.Should().Be(1);
+		memoryStreamFactory.Created.Count.Should().Be(2);
 		foreach (var memoryStream in memoryStreamFactory.Created)
-		{
 			memoryStream.IsDisposed.Should().BeTrue();
-		}
 	}
 
 	[Fact]