Implement SingleRow for multiple result sets. Fixes #681

Author: bgrainger

src/MySqlConnector/MySql.Data.MySqlClient/MySqlDataReader.cs

@@ -55,39 +55,43 @@ internal async Task<bool> NextResultAsync(IOBehavior ioBehavior, CancellationTok
 			VerifyNotDisposed();
 			try
 			{
-				while (true)
+				do
 				{
-					await m_resultSet!.ReadEntireAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
-					await ScanResultSetAsync(ioBehavior, m_resultSet, cancellationToken).ConfigureAwait(false);
-					if (m_hasMoreResults && m_resultSet.ContainsCommandParameters)
-						await ReadOutParametersAsync(Command!, m_resultSet, ioBehavior, cancellationToken).ConfigureAwait(false);
-					else
-						break;
-				}
+					while (true)
+					{
+						await m_resultSet!.ReadEntireAsync(ioBehavior, cancellationToken).ConfigureAwait(false);
+						await ScanResultSetAsync(ioBehavior, m_resultSet, cancellationToken).ConfigureAwait(false);
+						if (m_hasMoreResults && m_resultSet.ContainsCommandParameters)
+							await ReadOutParametersAsync(Command!, m_resultSet, ioBehavior, cancellationToken).ConfigureAwait(false);
+						else
+							break;
+					}
 
-				if (!m_hasMoreResults)
-				{
-					if (m_commandListPosition.CommandIndex < m_commandListPosition.Commands.Count)
+					if (!m_hasMoreResults)
 					{
-						Command = m_commandListPosition.Commands[m_commandListPosition.CommandIndex];
-						using (Command.CancellableCommand.RegisterCancel(cancellationToken))
+						if (m_commandListPosition.CommandIndex < m_commandListPosition.Commands.Count)
 						{
-							var writer = new ByteBufferWriter();
-							if (!Command.Connection!.Session.IsCancelingQuery && m_payloadCreator.WriteQueryCommand(ref m_commandListPosition, m_cachedProcedures!, writer))
+							Command = m_commandListPosition.Commands[m_commandListPosition.CommandIndex];
+							using (Command.CancellableCommand.RegisterCancel(cancellationToken))
 							{
-								using var payload = writer.ToPayloadData();
-								await Command.Connection.Session.SendAsync(payload, ioBehavior, cancellationToken).ConfigureAwait(false);
-								await m_resultSet.ReadResultSetHeaderAsync(ioBehavior).ConfigureAwait(false);
-								ActivateResultSet();
-								m_hasMoreResults = true;
+								var writer = new ByteBufferWriter();
+								if (!Command.Connection!.Session.IsCancelingQuery && m_payloadCreator.WriteQueryCommand(ref m_commandListPosition, m_cachedProcedures!, writer))
+								{
+									using var payload = writer.ToPayloadData();
+									await Command.Connection.Session.SendAsync(payload, ioBehavior, cancellationToken).ConfigureAwait(false);
+									await m_resultSet.ReadResultSetHeaderAsync(ioBehavior).ConfigureAwait(false);
+									ActivateResultSet();
+									m_hasMoreResults = true;
+								}
 							}
 						}
 					}
+					else
+					{
+						ActivateResultSet();
+					}
 				}
-				else
-				{
-					ActivateResultSet();
-				}
+				while (m_hasMoreResults && (Command!.CommandBehavior & CommandBehavior.SingleRow) != 0);
 
 				if (!m_hasMoreResults)
 					m_resultSet.Reset();

tests/SideBySide/QueryTests.cs

@@ -1071,6 +1071,32 @@ public void CommandBehaviorSingleRow()
 			Assert.False(reader.Read());
 		}
 
+		[Fact]
+		public async Task CommandBehaviorSingleRowMultipleResultSets()
+		{
+			using var connection = new MySqlConnection(AppConfig.ConnectionString);
+			connection.Open();
+			connection.Execute(@"drop table if exists command_behavior_single_row;
+create table command_behavior_single_row(id integer not null primary key);");
+
+			using (var cmd = new MySqlCommand("SELECT 1; insert into command_behavior_single_row(id) values(1); SELECT 2;", connection))
+			{
+				using var reader = await cmd.ExecuteReaderAsync(CommandBehavior.SingleRow);
+				Assert.True(await reader.ReadAsync());
+				Assert.Equal(1, reader.GetInt32(0));
+				Assert.False(await reader.ReadAsync());
+#if !BASELINE
+				Assert.False(await reader.NextResultAsync());
+#endif
+			}
+
+			// subsequent commands were still executed (and had effects) even though they didn't return results
+			using (var cmd = new MySqlCommand("select count(*) from command_behavior_single_row;", connection))
+			{
+				Assert.Equal(1L, await cmd.ExecuteScalarAsync());
+			}
+		}
+
 #if !BASELINE
 		[Fact]
 		public void NoBackslashEscapes()