Use ExceptionDispatchInfo to preserve the stack trace.

This avoid unnecessarily rewrapping a MySqlException in another MySqlException.

Author: bgrainger

src/MySqlConnector/Core/ResultSet.cs

@@ -4,6 +4,7 @@
 using System.Data;
 using System.Globalization;
 using System.IO;
+using System.Runtime.ExceptionServices;
 using System.Threading;
 using System.Threading.Tasks;
 using MySqlConnector.Protocol;
@@ -110,7 +111,7 @@ public async Task ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 						catch (Exception ex)
 						{
 							// store the exception, to be thrown after reading the response packet from the server
-							ReadResultSetHeaderException = new("Error during LOAD DATA LOCAL INFILE", ex);
+							ReadResultSetHeaderException = ExceptionDispatchInfo.Capture(new MySqlException("Error during LOAD DATA LOCAL INFILE", ex));
 						}
 
 						await Session.SendReplyAsync(EmptyPayload.Instance, ioBehavior, CancellationToken.None).ConfigureAwait(false);
@@ -166,7 +167,7 @@ int ReadColumnCount(ReadOnlySpan<byte> span)
 			}
 			catch (Exception ex)
 			{
-				ReadResultSetHeaderException = ex;
+				ReadResultSetHeaderException = ExceptionDispatchInfo.Capture(ex);
 			}
 			finally
 			{
@@ -425,7 +426,7 @@ public Row GetCurrentRow()
 		}
 
 		public readonly MySqlDataReader DataReader;
-		public Exception? ReadResultSetHeaderException { get; private set; }
+		public ExceptionDispatchInfo? ReadResultSetHeaderException { get; private set; }
 		public IMySqlCommand Command => DataReader.Command!;
 		public MySqlConnection Connection => DataReader.Connection!;
 		public ServerSession Session => DataReader.Session!;

src/MySqlConnector/MySqlDataReader.cs

@@ -7,6 +7,7 @@
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Runtime.ExceptionServices;
 using System.Threading;
 using System.Threading.Tasks;
 using MySqlConnector.Core;
@@ -117,12 +118,12 @@ private void ActivateResultSet(CancellationToken cancellationToken)
 		{
 			if (m_resultSet!.ReadResultSetHeaderException is not null)
 			{
-				var mySqlException = m_resultSet.ReadResultSetHeaderException as MySqlException;
+				var mySqlException = m_resultSet.ReadResultSetHeaderException.SourceException as MySqlException;
 
 				// for any exception not created from an ErrorPayload, mark the session as failed (because we can't guarantee that all data
 				// has been read from the connection and that the socket is still usable)
 				if (mySqlException?.SqlState is null)
-					Command!.Connection!.SetSessionFailed(m_resultSet.ReadResultSetHeaderException);
+					Command!.Connection!.SetSessionFailed(m_resultSet.ReadResultSetHeaderException.SourceException);
 
 				if (mySqlException?.ErrorCode == MySqlErrorCode.QueryInterrupted && cancellationToken.IsCancellationRequested)
 					throw new OperationCanceledException(mySqlException.Message, mySqlException, cancellationToken);
@@ -131,9 +132,9 @@ private void ActivateResultSet(CancellationToken cancellationToken)
 					throw MySqlException.CreateForTimeout(mySqlException);
 
 				if (mySqlException is not null)
-					throw new MySqlException(mySqlException.ErrorCode, mySqlException.SqlState, mySqlException.Message, mySqlException);
+					m_resultSet.ReadResultSetHeaderException.Throw();
 
-				throw new MySqlException("Failed to read the result set.", m_resultSet.ReadResultSetHeaderException);
+				throw new MySqlException("Failed to read the result set.", m_resultSet.ReadResultSetHeaderException.SourceException);
 			}
 
 			Command!.SetLastInsertedId(m_resultSet.LastInsertId);

tests/MySqlConnector.Tests/CancellationTests.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Data;
 using System.Diagnostics;
+using System.Net.Sockets;
 using System.Threading;
 using System.Threading.Tasks;
 using Xunit;
@@ -224,6 +225,7 @@ public void Test(int step, int method)
 				Assert.InRange(stopwatch.ElapsedMilliseconds, 2900, 3500);
 				Assert.Equal(MySqlErrorCode.CommandTimeoutExpired, ex.ErrorCode);
 				Assert.True(ex.IsTransient);
+				Assert.Null(ex.InnerException);
 
 				// connection is unusable
 				Assert.Equal(ConnectionState.Closed, connection.State);
@@ -245,6 +247,7 @@ public async Task Test(int step, int method)
 				var ex = await Assert.ThrowsAsync<MySqlException>(async () => await s_executeAsyncMethods[method](command, default));
 				Assert.InRange(stopwatch.ElapsedMilliseconds, 2900, 3500);
 				Assert.Equal(MySqlErrorCode.CommandTimeoutExpired, ex.ErrorCode);
+				Assert.IsType<SocketException>(ex.InnerException);
 
 				// connection is unusable
 				Assert.Equal(ConnectionState.Closed, connection.State);
@@ -267,6 +270,7 @@ public void Test(int step, int method)
 				var ex = Assert.Throws<MySqlException>(() => s_executeMethods[method](command));
 				Assert.InRange(stopwatch.ElapsedMilliseconds, 900, 1500);
 				Assert.Equal(MySqlErrorCode.CommandTimeoutExpired, ex.ErrorCode);
+				Assert.Null(ex.InnerException);
 
 				// connection is unusable
 				Assert.Equal(ConnectionState.Closed, connection.State);
@@ -289,6 +293,7 @@ public async Task Test(int step, int method)
 				var ex = await Assert.ThrowsAsync<MySqlException>(async () => await s_executeAsyncMethods[method](command, default));
 				Assert.InRange(stopwatch.ElapsedMilliseconds, 900, 1500);
 				Assert.Equal(MySqlErrorCode.CommandTimeoutExpired, ex.ErrorCode);
+				Assert.IsType<SocketException>(ex.InnerException);
 
 				// connection is unusable
 				Assert.Equal(ConnectionState.Closed, connection.State);