Keep the server count for INSERT ... RETURNING

Firebird classifies INSERT ... RETURNING and DML inside an execute
block as stored procedure execution, so the statement-type switch
reported -1 for them and the reader stopped reporting the insert count
it used to report. Count stored procedure execution only when the
server reports a positive count, so procedures that change no rows
keep -1.

Also set RecordsAffected to -1 in the FbDataReader constructor instead
of the field initializer, as requested in review.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

Author: alaricd

src/FirebirdSql.Data.FirebirdClient.Tests/FbDataReaderTests.cs

@@ -549,4 +549,46 @@ public async Task RecordsAffectedIsMinusOneForSelectTest()
 			Assert.AreEqual(-1, reader.RecordsAffected);
 		}
 	}
+
+	[Test]
+	public async Task RecordsAffectedForInsertReturningTest()
+	{
+		// INSERT ... RETURNING is classified by Firebird as a stored procedure execution, not as an INSERT.
+		await using (var transaction = await Connection.BeginTransactionAsync())
+		{
+			await using (var command = new FbCommand("insert into test (int_field) values (100001) returning int_field", Connection, transaction))
+			{
+				await using (var reader = await command.ExecuteReaderAsync())
+				{
+					while (await reader.ReadAsync())
+					{ }
+					Assert.AreEqual(1, reader.RecordsAffected);
+				}
+			}
+			await transaction.RollbackAsync();
+		}
+	}
+
+	[Test]
+	public async Task ExecuteNonQueryForStatementWithoutRowChangesIsMinusOneTest()
+	{
+		// Stored procedure execution that changes no rows keeps the -1 of "all other types of statements".
+		await using (var command = new FbCommand("execute block as begin end", Connection))
+		{
+			Assert.AreEqual(-1, await command.ExecuteNonQueryAsync());
+		}
+	}
+
+	[Test]
+	public async Task ExecuteNonQueryForInsertReturningTest()
+	{
+		await using (var transaction = await Connection.BeginTransactionAsync())
+		{
+			await using (var command = new FbCommand("insert into test (int_field) values (100002) returning int_field", Connection, transaction))
+			{
+				Assert.AreEqual(1, await command.ExecuteNonQueryAsync());
+			}
+			await transaction.RollbackAsync();
+		}
+	}
 }

src/FirebirdSql.Data.FirebirdClient/FirebirdClient/FbCommand.cs

@@ -266,6 +266,8 @@ internal int RecordsAffected
 	/// <summary>
 	/// The rows an INSERT, UPDATE or DELETE affected, or -1 for any other statement (DbCommand.ExecuteNonQuery: "For all
 	/// other types of statements, the return value is -1"; DbDataReader.RecordsAffected: "-1 for SELECT statements").
+	/// Firebird classifies INSERT ... RETURNING and DML inside an execute block as stored procedure execution; the server's
+	/// count is reported for those only when it is positive, so procedures that change no rows keep -1.
 	/// </summary>
 	internal int StatementRecordsAffected
 	{
@@ -276,6 +278,7 @@ internal int StatementRecordsAffected
 				DbStatementType.Insert => RecordsAffected,
 				DbStatementType.Update => RecordsAffected,
 				DbStatementType.Delete => RecordsAffected,
+				DbStatementType.StoredProcedure when RecordsAffected > 0 => RecordsAffected,
 				_ => -1,
 			};
 		}

src/FirebirdSql.Data.FirebirdClient/FirebirdClient/FbDataReader.cs

@@ -51,7 +51,7 @@ public sealed class FbDataReader : DbDataReader
 	private bool _eof;
 	private bool _isClosed;
 	private int _position;
-	private int _recordsAffected = -1;
+	private int _recordsAffected;
 	private Dictionary<string, int> _columnsIndexesOrdinal;
 	private Dictionary<string, int> _columnsIndexesOrdinalCI;
 
@@ -84,6 +84,7 @@ internal FbDataReader(FbCommand command, FbConnection connection, CommandBehavio
 		_connection = connection;
 		_commandBehavior = commandBehavior;
 		_fields = _command.GetFieldsDescriptor();
+		_recordsAffected = -1;
 
 		UpdateRecordsAffected();
 	}