Set MySqlCommand.CommandText to empty string by default. Fixes #743

Author: bgrainger

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

@@ -40,7 +40,7 @@ public MySqlCommand(string? commandText, MySqlConnection? connection, MySqlTrans
 		{
 			GC.SuppressFinalize(this);
 			m_commandId = ICancellableCommandExtensions.GetNextId();
-			CommandText = commandText;
+			m_commandText = commandText ?? "";
 			Connection = connection;
 			Transaction = transaction;
 			CommandType = CommandType.Text;
@@ -144,14 +144,15 @@ private bool NeedsPrepare(out Exception? exception)
 			return Connection.Session.TryGetPreparedStatement(CommandText!) is null;
 		}
 
-		public override string? CommandText
+		[AllowNull]
+		public override string CommandText
 		{
 			get => m_commandText;
 			set
 			{
 				if (m_connection?.HasActiveReader ?? false)
 					throw new InvalidOperationException("Cannot set MySqlCommand.CommandText when there is an open DataReader for this command; it must be closed first.");
-				m_commandText = value;
+				m_commandText = value ?? "";
 			}
 		}
 
@@ -360,7 +361,7 @@ private bool IsValid([NotNullWhen(false)] out Exception? exception)
 		readonly int m_commandId;
 		bool m_isDisposed;
 		MySqlConnection? m_connection;
-		string? m_commandText;
+		string m_commandText;
 		MySqlParameterCollection? m_parameterCollection;
 		int? m_commandTimeout;
 		CommandType m_commandType;

tests/SideBySide/CommandTests.cs

@@ -14,6 +14,36 @@ public CommandTests(DatabaseFixture database)
 			m_database = database;
 		}
 
+		[Fact]
+		public void CommandTextIsEmptyStringByDefault()
+		{
+			using var command = new MySqlCommand();
+			Assert.Equal("", command.CommandText);
+		}
+
+		[Fact]
+		public void InitializeWithNullCommandText()
+		{
+			using var command = new MySqlCommand(default(string));
+			Assert.Equal("", command.CommandText);
+		}
+
+		[Fact]
+		public void SetCommandTextToNull()
+		{
+			using var command = new MySqlCommand();
+			command.CommandText = null;
+			Assert.Equal("", command.CommandText);
+		}
+
+		[Fact]
+		public void SetCommandTextToEmptyString()
+		{
+			using var command = new MySqlCommand();
+			command.CommandText = "";
+			Assert.Equal("", command.CommandText);
+		}
+
 		[Fact]
 		public void CreateCommandSetsConnection()
 		{