Modifying to use rounding direction in RoundedDecimalField.

drf_braces/fields/custom.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import, print_function, unicode_literals
 import inspect
+from decimal import Decimal, getcontext
 
 import pytz
 import six
@@ -69,8 +70,9 @@ class RoundedDecimalField(fields.DecimalField):
     to two decimal places.
     """
 
-    def __init__(self, max_digits=None, decimal_places=2, *args, **kwargs):
-        max_digits = max_digits or self.MAX_STRING_LENGTH
+    def __init__(self, max_digits=None, decimal_places=2, rounding=None, *args, **kwargs):
+        self.rounding = rounding
+
         super(RoundedDecimalField, self).__init__(
             max_digits=max_digits,
             decimal_places=decimal_places,
@@ -83,6 +85,24 @@ def to_internal_value(self, data):
     def validate_precision(self, data):
         return data
 
+    def quantize(self, data):
+        """
+        Quantize the decimal value to the configured precision.
+        """
+        if self.decimal_places is None:
+            return data
+
+        context = getcontext().copy()
+
+        if self.max_digits is not None:
+            context.prec = self.max_digits
+        if self.rounding is not None:
+            context.rounding = self.rounding
+        return data.quantize(
+            Decimal('.1') ** self.decimal_places,
+            context=context
+        )
+
 
 __all__ = [name for name, value in locals().items()
            if inspect.isclass(value) and issubclass(value, fields.Field)]

drf_braces/tests/fields/test_custom.py

@@ -1,7 +1,7 @@
 from __future__ import absolute_import, print_function, unicode_literals
 import unittest
 from collections import OrderedDict
-from decimal import Decimal
+from decimal import ROUND_DOWN, Decimal
 
 import mock
 import pytz
@@ -62,8 +62,11 @@ def test_to_internal_value(self):
 class TestRoundedDecimalField(unittest.TestCase):
     def test_init(self):
         field = RoundedDecimalField()
-        self.assertIsNotNone(field.max_digits)
         self.assertEqual(field.decimal_places, 2)
+        self.assertIsNone(field.rounding)
+
+        new_field = RoundedDecimalField(rounding=ROUND_DOWN)
+        self.assertEqual(new_field.rounding, ROUND_DOWN)
 
     def test_to_internal_value(self):
         field = RoundedDecimalField()
@@ -83,3 +86,9 @@ def test_to_internal_value(self):
         self.assertEqual(field.to_internal_value(Decimal('5.2345')), Decimal('5.23'))
         self.assertEqual(field.to_internal_value(Decimal('5.2356')), Decimal('5.24'))
         self.assertEqual(field.to_internal_value(Decimal('4.2399')), Decimal('4.24'))
+
+        floored_field = RoundedDecimalField(rounding=ROUND_DOWN)
+        self.assertEqual(floored_field.to_internal_value(5.2345), Decimal('5.23'))
+        self.assertEqual(floored_field.to_internal_value(5.2356), Decimal('5.23'))
+        self.assertEqual(floored_field.to_internal_value(Decimal('5.2345')), Decimal('5.23'))
+        self.assertEqual(floored_field.to_internal_value(Decimal('5.2356')), Decimal('5.23'))