Add MySqlConnection.InfoMessage event. Fixes #594

Author: bgrainger

src/MySqlConnector/Core/ResultSet.cs

@@ -28,6 +28,7 @@ public async Task<ResultSet> ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 			ColumnTypes = null;
 			LastInsertId = 0;
 			RecordsAffected = null;
+			WarningCount = 0;
 			State = ResultSetState.None;
 			m_columnDefinitionPayloadUsedBytes = 0;
 			m_readBuffer.Clear();
@@ -47,6 +48,7 @@ public async Task<ResultSet> ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 						var ok = OkPayload.Create(payload.AsSpan());
 						RecordsAffected = (RecordsAffected ?? 0) + ok.AffectedRowCount;
 						LastInsertId = unchecked((long) ok.LastInsertId);
+						WarningCount = ok.WarningCount;
 						if (ok.NewSchema != null)
 							Connection.Session.DatabaseOverride = ok.NewSchema;
 						ColumnDefinitions = null;
@@ -128,6 +130,7 @@ int ReadColumnCount(ReadOnlySpan<byte> span)
 						}
 
 						LastInsertId = -1;
+						WarningCount = 0;
 						State = ResultSetState.ReadResultSetHeader;
 						break;
 					}
@@ -329,6 +332,7 @@ public Row GetCurrentRow()
 		public MySqlDbType[] ColumnTypes { get; private set; }
 		public long LastInsertId { get; private set; }
 		public int? RecordsAffected { get; private set; }
+		public int WarningCount { get; private set; }
 		public ResultSetState State { get; private set; }
 
 		ResizableArray<byte> m_columnDefinitionPayloads;

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

@@ -309,6 +309,8 @@ private SchemaProvider GetSchemaProvider()
 
 		public override int ConnectionTimeout => m_connectionSettings.ConnectionTimeout;
 
+		public event MySqlInfoMessageEventHandler InfoMessage;
+
 		protected override void Dispose(bool disposing)
 		{
 			try
@@ -444,10 +446,23 @@ internal void SetActiveReader(MySqlDataReader dataReader)
 			m_activeReader = dataReader;
 		}
 
-		internal void FinishQuerying()
+		internal void FinishQuerying(bool hasWarnings)
 		{
 			m_session.FinishQuerying();
 			m_activeReader = null;
+
+			if (hasWarnings && InfoMessage != null)
+			{
+				var errors = new List<MySqlError>();
+				using (var command = new MySqlCommand("SHOW WARNINGS;", this))
+				using (var reader = command.ExecuteReader())
+				{
+					while (reader.Read())
+						errors.Add(new MySqlError(reader.GetString(0), reader.GetInt32(1), reader.GetString(2)));
+				}
+
+				InfoMessage(this, new MySqlInfoMessageEventArgs(errors.ToArray()));
+			}
 		}
 
 		private async ValueTask<ServerSession> CreateSessionAsync(IOBehavior? ioBehavior, CancellationToken cancellationToken)

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

@@ -94,6 +94,7 @@ private void ActivateResultSet(ResultSet resultSet)
 
 			Command.LastInsertedId = resultSet.LastInsertId;
 			m_recordsAffected = m_recordsAffected == null ? resultSet.RecordsAffected : m_recordsAffected.Value + (resultSet.RecordsAffected ?? 0);
+			m_hasWarnings = resultSet.WarningCount != 0;
 		}
 
 		private ValueTask<ResultSet> ScanResultSetAsync(IOBehavior ioBehavior, ResultSet resultSet, CancellationToken cancellationToken)
@@ -431,7 +432,7 @@ private void DoClose()
 				m_resultSetBuffered = null;
 
 				var connection = Command.Connection;
-				connection.FinishQuerying();
+				connection.FinishQuerying(m_hasWarnings);
 
 				Command.ReaderClosed();
 				if ((m_behavior & CommandBehavior.CloseConnection) != 0)
@@ -458,6 +459,7 @@ private ResultSet GetResultSet()
 		readonly CommandBehavior m_behavior;
 		bool m_closed;
 		int? m_recordsAffected;
+		bool m_hasWarnings;
 		ResultSet m_resultSet;
 		ResultSet m_resultSetBuffered;
 #if !NETSTANDARD1_3

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

@@ -0,0 +1,16 @@
+namespace MySql.Data.MySqlClient
+{
+	public sealed class MySqlError
+	{
+		internal MySqlError(string level, int code, string message)
+		{
+			Level = level;
+			Code = code;
+			Message = message;
+		}
+
+		public string Level { get; }
+		public int Code { get; }
+		public string Message { get; }
+	};
+}

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

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+
+namespace MySql.Data.MySqlClient
+{
+	public sealed class MySqlInfoMessageEventArgs : EventArgs
+	{
+		internal MySqlInfoMessageEventArgs(MySqlError[] errors) => this.errors = errors;
+
+		public MySqlError[] errors { get; }
+
+		public IReadOnlyList<MySqlError> Errors => errors;
+	}
+
+	public delegate void MySqlInfoMessageEventHandler(object sender, MySqlInfoMessageEventArgs args);
+}

tests/SideBySide/ConnectionTests.cs

@@ -0,0 +1,58 @@
+using Dapper;
+using MySql.Data.MySqlClient;
+using Xunit;
+
+namespace SideBySide
+{
+	public class ConnectionTests : IClassFixture<DatabaseFixture>
+	{
+		public ConnectionTests(DatabaseFixture database)
+		{
+		}
+
+		[Fact]
+		public void GotInfoMessageForNonExistentTable()
+		{
+			using (var connection = new MySqlConnection(AppConfig.ConnectionString))
+			{
+				connection.Open();
+
+				var gotEvent = false;
+				connection.InfoMessage += (s, a) =>
+				{
+					gotEvent = true;
+					Assert.Single(a.errors);
+					Assert.Equal((int) MySqlErrorCode.BadTable, a.errors[0].Code);
+				};
+
+				connection.Execute(@"drop table if exists table_does_not_exist;");
+				Assert.True(gotEvent);
+			}
+		}
+
+		[Fact]
+		public void NoInfoMessageWhenNotLastStatementInBatch()
+		{
+			using (var connection = new MySqlConnection(AppConfig.ConnectionString))
+			{
+				connection.Open();
+
+				var gotEvent = false;
+				connection.InfoMessage += (s, a) =>
+				{
+					gotEvent = true;
+
+					// seeming bug in Connector/NET raises an event with no errors
+					Assert.Empty(a.errors);
+				};
+
+				connection.Execute(@"drop table if exists table_does_not_exist; select 1;");
+#if BASELINE
+				Assert.True(gotEvent);
+#else
+				Assert.False(gotEvent);
+#endif
+			}
+		}
+	}
+}