Prevent the same reader being closed twice. Fixes #423

Dispose(bool) calls DoClose then (on certain frameworks) base.Dispose(bool) calls Close, which calls DoClose again.

This normally wouldn't be a problem except that when a stored procedure has OUT parameters, they are read from a nested MySqlDataReader. This reentrancy allows a reader to be closed twice if an exception is thrown, which masks the underlying exception and throws InvalidOperationExcepion "Expected state to be Failed but was Connected" instead.

Author: bgrainger

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

@@ -396,8 +396,10 @@ private MySqlDataReader(MySqlCommand command, CommandBehavior behavior)
 
 		private void DoClose()
 		{
-			if (Command != null)
+			if (!m_closed)
 			{
+				m_closed = true;
+
 				if (m_resultSet != null)
 				{
 					Command.Connection.Session.SetTimeout(Constants.InfiniteTimeout);
@@ -443,6 +445,7 @@ private ResultSet GetResultSet()
 		}
 
 		readonly CommandBehavior m_behavior;
+		bool m_closed;
 		int? m_recordsAffected;
 		ResultSet m_resultSet;
 		ResultSet m_resultSetBuffered;

tests/SideBySide/StoredProcedureFixture.cs

@@ -1,4 +1,4 @@
-using Dapper;
+using Dapper;
 
 namespace SideBySide
 {
@@ -48,6 +48,13 @@ OUT shape VARCHAR(63)
 					SELECT 'circle' INTO shape;
 					SELECT CONCAT(name, shape);
 				END");
+			Connection.Execute(@"DROP PROCEDURE IF EXISTS out_string;
+				CREATE PROCEDURE out_string(
+					OUT value VARCHAR(100)
+				)
+				BEGIN
+					SELECT 'test value' INTO value;
+				END");
 			Connection.Execute(@"drop table if exists sproc_multiple_rows;
 				create table sproc_multiple_rows (
 					value integer not null primary key auto_increment,

tests/SideBySide/StoredProcedureTests.cs

@@ -117,6 +117,24 @@ public async Task StoredProcedureEchoException(string procedureType)
 			}
 		}
 
+		[Fact]
+		public async Task StoredProcedureOutIncorrectType()
+		{
+			using (var cmd = m_database.Connection.CreateCommand())
+			{
+				cmd.CommandText = "out_string";
+				cmd.CommandType = CommandType.StoredProcedure;
+				cmd.Parameters.Add(new MySqlParameter
+				{
+					ParameterName = "@value",
+					DbType = DbType.Double,
+					Direction = ParameterDirection.Output,
+				});
+
+				await Assert.ThrowsAsync<FormatException>(cmd.ExecuteNonQueryAsync);
+			}
+		}
+
 		[Theory]
 		[InlineData("NonQuery")]
 		[InlineData("Scalar")]