Fix incorrect NumericPrecision. Fixes #356

Author: bgrainger

docs/content/tutorials/migrating-from-connector-net.md

@@ -95,3 +95,4 @@ property doesn't reference the active transaction. See [#333](https://github.com
 * [#86263](https://bugs.mysql.com/bug.php?id=86263): Transaction isolation level affects all transactions in session
 * [#87868](https://bugs.mysql.com/bug.php?id=87868): `ColumnSize` in schema table is incorrect for `CHAR(36)` and `BLOB` columns
 * [#87876](https://bugs.mysql.com/bug.php?id=87876): `IsLong` is schema table is incorrect for `LONGTEXT` and `LONGBLOB` columns
+* [#88058](https://bugs.mysql.com/bug.php?id=88058): `decimal(n, 0)` has wrong `NumericPrecision`

src/MySqlConnector/MySqlClient/MySqlDbColumn.cs

@@ -35,7 +35,13 @@ internal MySqlDbColumn(int ordinal, ColumnDefinitionPayload column, Type type, s
 			IsReadOnly = false;
 			IsUnique = (column.ColumnFlags & ColumnFlags.UniqueKey) != 0;
 			if (column.ColumnType == ColumnType.Decimal || column.ColumnType == ColumnType.NewDecimal)
-				NumericPrecision = (int) (column.ColumnLength - 2 + ((column.ColumnFlags & ColumnFlags.Unsigned) != 0 ? 1 : 0));
+			{
+				NumericPrecision = (int) column.ColumnLength;
+				if ((column.ColumnFlags & ColumnFlags.Unsigned) == 0)
+					NumericPrecision--;
+				if (column.Decimals > 0)
+					NumericPrecision--;
+			}
 			NumericScale = column.Decimals;
 			ProviderType = (int) column.ColumnType;
 		}

tests/SideBySide/DataTypes.cs

@@ -648,7 +648,33 @@ public void InsertLargeBlobSync(string column, int size)
 		[InlineData("Timestamp", "datatypes_times", 26, typeof(DateTime), "N", 0, 6)]
 		[InlineData("Time", "datatypes_times", 17, typeof(TimeSpan), "N", 0, 6)]
 		[InlineData("Year", "datatypes_times", 4, typeof(int), "N", 0, 0)]
-		public void GetSchemaTable(string column, string table, int columnSize, Type dataType, string flags, int precision, int scale)
+		public void GetSchemaTable(string column, string table, int columnSize, Type dataType, string flags, int precision, int scale) =>
+			DoGetSchemaTable(column, table, columnSize, dataType, flags, precision, scale);
+
+		[Theory]
+		[InlineData("`decimal-type` decimal(10,0) NOT NULL", "decimal-type", 11, typeof(decimal), "", 10, 0
+#if BASELINE
+			, Skip = "https://bugs.mysql.com/bug.php?id=88058"
+#endif
+			)]
+		[InlineData("`decimal-type` decimal(10,1) NOT NULL", "decimal-type", 12, typeof(decimal), "", 10, 1)]
+		[InlineData("`decimal-type` decimal(10,0) UNSIGNED NOT NULL", "decimal-type", 10, typeof(decimal), "", 10, 0
+#if BASELINE
+			, Skip = "https://bugs.mysql.com/bug.php?id=88058"
+#endif
+			)]
+		[InlineData("`decimal-type` decimal(10,1) UNSIGNED NOT NULL", "decimal-type", 11, typeof(decimal), "", 10, 1)]
+		[InlineData("`decimal-type` decimal(65,30) NOT NULL", "decimal-type", 67, typeof(decimal), "", 65, 30)]
+		[InlineData("`decimal-type` decimal(1,1) NOT NULL", "decimal-type", 3, typeof(decimal), "", 1, 1)]
+		public void GetSchemaTableForNewColumn(string createColumn, string column, int columnSize, Type dataType, string flags, int precision, int scale)
+		{
+			m_database.Connection.Execute($@"drop table if exists schema_table;
+create table schema_table({createColumn});");
+
+			DoGetSchemaTable(column, "schema_table", columnSize, dataType, flags, precision, scale);
+		}
+
+		private void DoGetSchemaTable(string column, string table, int columnSize, Type dataType, string flags, int precision, int scale)
 		{
 			if (table == "datatypes_json_core" && !AppConfig.SupportsJson)
 				return;