Return empty schema when there is no result set. Fixes #744

Author: bgrainger

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

@@ -300,12 +300,12 @@ public override long GetChars(int ordinal, long dataOffset, char[]? buffer, int
 
 		public ReadOnlyCollection<DbColumn> GetColumnSchema()
 		{
-			var columnDefinitions = GetResultSet().ColumnDefinitions;
-			if (columnDefinitions is null)
-				throw new InvalidOperationException("There is no current result set.");
-			return columnDefinitions
-				.Select((c, n) => (DbColumn) new MySqlDbColumn(n, c, Connection!.AllowZeroDateTime, GetResultSet().ColumnTypes![n]))
-				.ToList().AsReadOnly();
+			var columnDefinitions = m_resultSet?.ColumnDefinitions;
+			var hasNoSchema = columnDefinitions is null || m_resultSet!.ContainsCommandParameters;
+			return hasNoSchema ? new List<DbColumn>().AsReadOnly() :
+				columnDefinitions!
+					.Select((c, n) => (DbColumn) new MySqlDbColumn(n, c, Connection!.AllowZeroDateTime, GetResultSet().ColumnTypes![n]))
+					.ToList().AsReadOnly();
 		}
 
 		public override T GetFieldValue<T>(int ordinal)
@@ -411,11 +411,11 @@ internal static async Task<MySqlDataReader> CreateAsync(CommandListPosition comm
 #if !NETSTANDARD1_3
 		internal DataTable BuildSchemaTable()
 		{
-			var colDefinitions = GetResultSet().ColumnDefinitions;
-			if (colDefinitions is null)
-				throw new InvalidOperationException("There is no current result set.");
-			DataTable schemaTable = new DataTable("SchemaTable");
-			schemaTable.Locale = CultureInfo.InvariantCulture;
+			var schemaTable = new DataTable("SchemaTable") { Locale = CultureInfo.InvariantCulture };
+
+			var colDefinitions = m_resultSet?.ColumnDefinitions;
+			if (colDefinitions is null || m_resultSet!.ContainsCommandParameters)
+				return schemaTable;
 			schemaTable.MinimumCapacity = colDefinitions.Length;
 
 			var columnName = new DataColumn(SchemaTableColumn.ColumnName, typeof(string));

tests/Conformance.Tests/DataReaderTests.cs

@@ -12,5 +12,8 @@ public DataReaderTests(SelectValueFixture fixture)
 
 		[Fact(Skip = "Deliberately throws InvalidCastException")]
 		public override void GetTextReader_returns_empty_for_null_String() { }
+
+		[Fact(Skip = "https://github.com/mysql-net/MySqlConnector/issues/744")]
+		public override void GetSchemaTable_throws_after_Delete() { }
 	}
 }

tests/SideBySide/DataTypes.cs

@@ -1174,7 +1174,10 @@ public void GetSchemaTableAfterNextResult()
 #if BASELINE
 			Assert.Null(reader.GetSchemaTable());
 #else
-			Assert.Throws<InvalidOperationException>(() => reader.GetSchemaTable());
+			table = reader.GetSchemaTable();
+			Assert.NotNull(table);
+			Assert.Empty(table.Rows);
+			Assert.Empty(table.Columns);
 #endif
 		}
 #endif

tests/SideBySide/QueryTests.cs

@@ -792,7 +792,7 @@ public void GetColumnSchemaAfterNextResult()
 			cmd.CommandText = "select 1;";
 			using var reader = cmd.ExecuteReader();
 			Assert.False(reader.NextResult());
-			Assert.Throws<InvalidOperationException>(() => reader.GetColumnSchema());
+			Assert.Empty(reader.GetColumnSchema());
 		}
 #endif
 

tests/SideBySide/StoredProcedureTests.cs

@@ -172,7 +172,33 @@ public async Task GetSchemaTableForNoResultSet()
 			using (var reader = await cmd.ExecuteReaderAsync())
 			{
 				Assert.False(await reader.ReadAsync());
-				Assert.Throws<InvalidOperationException>(() => reader.GetSchemaTable());
+				var table = reader.GetSchemaTable();
+				Assert.NotNull(table);
+				Assert.Empty(table.Rows);
+				Assert.Empty(table.Columns);
+				Assert.False(await reader.NextResultAsync());
+			}
+		}
+#endif
+
+#if !BASELINE
+		[Fact]
+		public async Task GetColumnSchemaForNoResultSet()
+		{
+			using var cmd = m_database.Connection.CreateCommand();
+			cmd.CommandText = "out_string";
+			cmd.CommandType = CommandType.StoredProcedure;
+			cmd.Parameters.Add(new MySqlParameter
+			{
+				ParameterName = "@value",
+				DbType = DbType.String,
+				Direction = ParameterDirection.Output,
+			});
+
+			using (var reader = (MySqlDataReader) await cmd.ExecuteReaderAsync())
+			{
+				Assert.False(await reader.ReadAsync());
+				Assert.Empty(reader.GetColumnSchema());
 				Assert.False(await reader.NextResultAsync());
 			}
 		}