FIX: Setinputsizes() SQL_DECIMAL crash

mssql_python/cursor.py

@@ -885,8 +885,8 @@ def _get_c_type_for_sql_type(self, sql_type: int) -> int:
             ddbc_sql_const.SQL_WCHAR.value: ddbc_sql_const.SQL_C_WCHAR.value,
             ddbc_sql_const.SQL_WVARCHAR.value: ddbc_sql_const.SQL_C_WCHAR.value,
             ddbc_sql_const.SQL_WLONGVARCHAR.value: ddbc_sql_const.SQL_C_WCHAR.value,
-            ddbc_sql_const.SQL_DECIMAL.value: ddbc_sql_const.SQL_C_NUMERIC.value,
-            ddbc_sql_const.SQL_NUMERIC.value: ddbc_sql_const.SQL_C_NUMERIC.value,
+            ddbc_sql_const.SQL_DECIMAL.value: ddbc_sql_const.SQL_C_CHAR.value,
+            ddbc_sql_const.SQL_NUMERIC.value: ddbc_sql_const.SQL_C_CHAR.value,
             ddbc_sql_const.SQL_BIT.value: ddbc_sql_const.SQL_C_BIT.value,
             ddbc_sql_const.SQL_TINYINT.value: ddbc_sql_const.SQL_C_TINYINT.value,
             ddbc_sql_const.SQL_SMALLINT.value: ddbc_sql_const.SQL_C_SHORT.value,
@@ -949,6 +949,14 @@ def _create_parameter_types_list(  # pylint: disable=too-many-arguments,too-many
                 # For non-NULL parameters, determine the appropriate C type based on SQL type
                 c_type = self._get_c_type_for_sql_type(sql_type)
 
+                # Convert Decimal to string for SQL_C_CHAR binding (GH-503)
+                if isinstance(parameter, decimal.Decimal) and sql_type in (
+                    ddbc_sql_const.SQL_DECIMAL.value,
+                    ddbc_sql_const.SQL_NUMERIC.value,
+                ):
+                    parameters_list[i] = format(parameter, "f")
+                    parameter = parameters_list[i]
+
                 # Check if this should be a DAE (data at execution) parameter
                 # For string types with large column sizes
                 if isinstance(parameter, str) and column_size > MAX_INLINE_CHAR:
@@ -2306,17 +2314,20 @@ def executemany(  # pylint: disable=too-many-locals,too-many-branches,too-many-s
                     and parameters_type[i].paramSQLType == ddbc_sql_const.SQL_VARCHAR.value
                 ):
                     processed_row[i] = format(val, "f")
-                # Existing numeric conversion
+                # Convert all values to string for DECIMAL/NUMERIC columns (GH-503)
                 elif parameters_type[i].paramSQLType in (
                     ddbc_sql_const.SQL_DECIMAL.value,
                     ddbc_sql_const.SQL_NUMERIC.value,
-                ) and not isinstance(val, decimal.Decimal):
-                    try:
-                        processed_row[i] = decimal.Decimal(str(val))
-                    except Exception as e:  # pylint: disable=broad-exception-caught
-                        raise ValueError(
-                            f"Failed to convert parameter at row {row}, column {i} to Decimal: {e}"
-                        ) from e
+                ):
+                    if isinstance(val, decimal.Decimal):
+                        processed_row[i] = format(val, "f")
+                    else:
+                        try:
+                            processed_row[i] = format(decimal.Decimal(str(val)), "f")
+                        except Exception as e:  # pylint: disable=broad-exception-caught
+                            raise ValueError(
+                                f"Failed to convert parameter at row {row}, column {i} to Decimal: {e}"
+                            ) from e
             processed_parameters.append(processed_row)
 
         # Now transpose the processed parameters

tests/test_004_cursor.py

@@ -9974,6 +9974,166 @@ def test_cursor_setinputsizes_with_executemany_float(db_connection):
     cursor.execute("DROP TABLE IF EXISTS #test_inputsizes_float")
 
 
+def test_setinputsizes_sql_decimal_with_executemany(db_connection):
+    """Test setinputsizes with SQL_DECIMAL accepts Python Decimal values (GH-503).
+
+    Without this fix, passing SQL_DECIMAL or SQL_NUMERIC via setinputsizes()
+    caused a RuntimeError because Decimal objects were not converted to
+    NumericData before the C binding validated the C type.
+    """
+    cursor = db_connection.cursor()
+
+    cursor.execute("DROP TABLE IF EXISTS #test_sis_decimal")
+    try:
+        cursor.execute("""
+        CREATE TABLE #test_sis_decimal (
+            Name NVARCHAR(100),
+            CategoryID INT,
+            Price DECIMAL(18,2)
+        )
+        """)
+
+        cursor.setinputsizes(
+            [
+                (mssql_python.SQL_WVARCHAR, 100, 0),
+                (mssql_python.SQL_INTEGER, 0, 0),
+                (mssql_python.SQL_DECIMAL, 18, 2),
+            ]
+        )
+
+        cursor.executemany(
+            "INSERT INTO #test_sis_decimal (Name, CategoryID, Price) VALUES (?, ?, ?)",
+            [
+                ("Widget", 1, decimal.Decimal("19.99")),
+                ("Gadget", 2, decimal.Decimal("29.99")),
+                ("Gizmo", 3, decimal.Decimal("0.01")),
+            ],
+        )
+
+        cursor.execute("SELECT Name, CategoryID, Price FROM #test_sis_decimal ORDER BY CategoryID")
+        rows = cursor.fetchall()
+
+        assert len(rows) == 3
+        assert rows[0][0] == "Widget"
+        assert rows[0][1] == 1
+        assert rows[0][2] == decimal.Decimal("19.99")
+        assert rows[1][0] == "Gadget"
+        assert rows[1][1] == 2
+        assert rows[1][2] == decimal.Decimal("29.99")
+        assert rows[2][0] == "Gizmo"
+        assert rows[2][1] == 3
+        assert rows[2][2] == decimal.Decimal("0.01")
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #test_sis_decimal")
+
+
+def test_setinputsizes_sql_numeric_with_executemany(db_connection):
+    """Test setinputsizes with SQL_NUMERIC accepts Python Decimal values (GH-503)."""
+    cursor = db_connection.cursor()
+
+    cursor.execute("DROP TABLE IF EXISTS #test_sis_numeric")
+    try:
+        cursor.execute("""
+        CREATE TABLE #test_sis_numeric (
+            Value NUMERIC(10,4)
+        )
+        """)
+
+        cursor.setinputsizes(
+            [
+                (mssql_python.SQL_NUMERIC, 10, 4),
+            ]
+        )
+
+        cursor.executemany(
+            "INSERT INTO #test_sis_numeric (Value) VALUES (?)",
+            [
+                (decimal.Decimal("123.4567"),),
+                (decimal.Decimal("-99.0001"),),
+                (decimal.Decimal("0.0000"),),
+            ],
+        )
+
+        cursor.execute("SELECT Value FROM #test_sis_numeric ORDER BY Value")
+        rows = cursor.fetchall()
+
+        assert len(rows) == 3
+        assert rows[0][0] == decimal.Decimal("-99.0001")
+        assert rows[1][0] == decimal.Decimal("0.0000")
+        assert rows[2][0] == decimal.Decimal("123.4567")
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #test_sis_numeric")
+
+
+def test_setinputsizes_sql_decimal_with_non_decimal_values(db_connection):
+    """Test setinputsizes with SQL_DECIMAL converts non-Decimal values (int/float) to string (GH-503)."""
+    cursor = db_connection.cursor()
+
+    cursor.execute("DROP TABLE IF EXISTS #test_sis_dec_nondec")
+    try:
+        cursor.execute("CREATE TABLE #test_sis_dec_nondc (Price DECIMAL(18,2))")
+
+        cursor.setinputsizes([(mssql_python.SQL_DECIMAL, 18, 2)])
+
+        # Pass int and float instead of Decimal — exercises the non-Decimal conversion branch
+        cursor.executemany(
+            "INSERT INTO #test_sis_dec_nondc (Price) VALUES (?)",
+            [(42,), (19.99,), (0,)],
+        )
+
+        cursor.execute("SELECT Price FROM #test_sis_dec_nondc ORDER BY Price")
+        rows = cursor.fetchall()
+
+        assert len(rows) == 3
+        assert rows[0][0] == decimal.Decimal("0.00")
+        assert rows[1][0] == decimal.Decimal("19.99")
+        assert rows[2][0] == decimal.Decimal("42.00")
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #test_sis_dec_nondc")
+
+
+def test_setinputsizes_sql_decimal_with_execute(db_connection):
+    """Test setinputsizes with SQL_DECIMAL works with single execute() too (GH-503)."""
+    cursor = db_connection.cursor()
+
+    cursor.execute("DROP TABLE IF EXISTS #test_sis_dec_exec")
+    try:
+        cursor.execute("CREATE TABLE #test_sis_dec_exec (Price DECIMAL(18,2))")
+
+        cursor.setinputsizes([(mssql_python.SQL_DECIMAL, 18, 2)])
+        cursor.execute(
+            "INSERT INTO #test_sis_dec_exec (Price) VALUES (?)",
+            decimal.Decimal("99.95"),
+        )
+
+        cursor.execute("SELECT Price FROM #test_sis_dec_exec")
+        row = cursor.fetchone()
+        assert row[0] == decimal.Decimal("99.95")
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #test_sis_dec_exec")
+
+
+def test_setinputsizes_sql_decimal_null(db_connection):
+    """Test setinputsizes with SQL_DECIMAL handles NULL values correctly (GH-503)."""
+    cursor = db_connection.cursor()
+
+    cursor.execute("DROP TABLE IF EXISTS #test_sis_dec_null")
+    try:
+        cursor.execute("CREATE TABLE #test_sis_dec_null (Price DECIMAL(18,2))")
+
+        cursor.setinputsizes([(mssql_python.SQL_DECIMAL, 18, 2)])
+        cursor.execute(
+            "INSERT INTO #test_sis_dec_null (Price) VALUES (?)",
+            None,
+        )
+
+        cursor.execute("SELECT Price FROM #test_sis_dec_null")
+        row = cursor.fetchone()
+        assert row[0] is None
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #test_sis_dec_null")
+
+
 def test_cursor_setinputsizes_reset(db_connection):
     """Test that setinputsizes is reset after execution"""