Add DecimalField support

4 files changed, 247 insertions, 0 deletions

diff --git a/docs/api-guide/fields.md b/docs/api-guide/fields.md
index 42f89f46..e117c370 100644
--- a/docs/api-guide/fields.md
+++ b/docs/api-guide/fields.md
@@ -248,6 +248,12 @@ A floating point representation.
 
 Corresponds to `django.db.models.fields.FloatField`.
 
+## DecimalField
+
+A decimal representation.
+
+Corresponds to `django.db.models.fields.DecimalField`.
+
 ## FileField
 
 A file representation. Performs Django's standard FileField validation. 
diff --git a/docs/topics/release-notes.md b/docs/topics/release-notes.md
index 609b4504..66022959 100644
--- a/docs/topics/release-notes.md
+++ b/docs/topics/release-notes.md
@@ -42,6 +42,7 @@ You can determine your currently installed version using `pip freeze`:
 
 ### Master
 
+* DecimalField support.
 * OAuth2 authentication no longer requires unneccessary URL parameters in addition to the token.
 * URL hyperlinking in browseable API now handles more cases correctly.
 * Long HTTP headers in browsable API are broken in multiple lines when possible.
diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index f3496b53..a1b9f546 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 
 import copy
 import datetime
+from decimal import Decimal, DecimalException
 import inspect
 import re
 import warnings
@@ -721,6 +722,80 @@ class FloatField(WritableField):
             raise ValidationError(msg)
 
 
+class DecimalField(WritableField):
+    type_name = 'DecimalField'
+    form_field_class = forms.DecimalField
+
+    default_error_messages = {
+        'invalid': _('Enter a number.'),
+        'max_value': _('Ensure this value is less than or equal to %(limit_value)s.'),
+        'min_value': _('Ensure this value is greater than or equal to %(limit_value)s.'),
+        'max_digits': _('Ensure that there are no more than %s digits in total.'),
+        'max_decimal_places': _('Ensure that there are no more than %s decimal places.'),
+        'max_whole_digits': _('Ensure that there are no more than %s digits before the decimal point.')
+    }
+
+    def __init__(self, max_value=None, min_value=None, max_digits=None, decimal_places=None, *args, **kwargs):
+        self.max_value, self.min_value = max_value, min_value
+        self.max_digits, self.decimal_places = max_digits, decimal_places
+        super(DecimalField, self).__init__(self, *args, **kwargs)
+
+        if max_value is not None:
+            self.validators.append(validators.MaxValueValidator(max_value))
+        if min_value is not None:
+            self.validators.append(validators.MinValueValidator(min_value))
+
+    def from_native(self, value):
+        """
+        Validates that the input is a decimal number. Returns a Decimal
+        instance. Returns None for empty values. Ensures that there are no more
+        than max_digits in the number, and no more than decimal_places digits
+        after the decimal point.
+        """
+        if value in validators.EMPTY_VALUES:
+            return None
+        value = smart_text(value).strip()
+        try:
+            value = Decimal(value)
+        except DecimalException:
+            raise ValidationError(self.error_messages['invalid'])
+        return value
+
+    def to_native(self, value):
+        if value is not None:
+            return str(value)
+        return value
+
+    def validate(self, value):
+        super(DecimalField, self).validate(value)
+        if value in validators.EMPTY_VALUES:
+            return
+        # Check for NaN, Inf and -Inf values. We can't compare directly for NaN,
+        # since it is never equal to itself. However, NaN is the only value that
+        # isn't equal to itself, so we can use this to identify NaN
+        if value != value or value == Decimal("Inf") or value == Decimal("-Inf"):
+            raise ValidationError(self.error_messages['invalid'])
+        sign, digittuple, exponent = value.as_tuple()
+        decimals = abs(exponent)
+        # digittuple doesn't include any leading zeros.
+        digits = len(digittuple)
+        if decimals > digits:
+            # We have leading zeros up to or past the decimal point.  Count
+            # everything past the decimal point as a digit.  We do not count
+            # 0 before the decimal point as a digit since that would mean
+            # we would not allow max_digits = decimal_places.
+            digits = decimals
+        whole_digits = digits - decimals
+
+        if self.max_digits is not None and digits > self.max_digits:
+            raise ValidationError(self.error_messages['max_digits'] % self.max_digits)
+        if self.decimal_places is not None and decimals > self.decimal_places:
+            raise ValidationError(self.error_messages['max_decimal_places'] % self.decimal_places)
+        if self.max_digits is not None and self.decimal_places is not None and whole_digits > (self.max_digits - self.decimal_places):
+            raise ValidationError(self.error_messages['max_whole_digits'] % (self.max_digits - self.decimal_places))
+        return value
+
+
 class FileField(WritableField):
     use_files = True
     type_name = 'FileField'
diff --git a/rest_framework/tests/fields.py b/rest_framework/tests/fields.py
index 19c663d8..f833aa32 100644
--- a/rest_framework/tests/fields.py
+++ b/rest_framework/tests/fields.py
@@ -3,12 +3,14 @@ General serializer field tests.
 """
 from __future__ import unicode_literals
 import datetime
+from decimal import Decimal
 
 from django.db import models
 from django.test import TestCase
 from django.core import validators
 
 from rest_framework import serializers
+from rest_framework.serializers import Serializer
 
 
 class TimestampedModel(models.Model):
@@ -481,3 +483,166 @@ class TimeFieldTest(TestCase):
         self.assertEqual('04 - 00 [000000]', result_1)
         self.assertEqual('04 - 59 [000000]', result_2)
         self.assertEqual('04 - 59 [000200]', result_3)
+
+
+class DecimalFieldTest(TestCase):
+    """
+    Tests for the DecimalField from_native() and to_native() behavior
+    """
+
+    def test_from_native_string(self):
+        """
+        Make sure from_native() accepts string values
+        """
+        f = serializers.DecimalField()
+        result_1 = f.from_native('9000')
+        result_2 = f.from_native('1.00000001')
+
+        self.assertEqual(Decimal('9000'), result_1)
+        self.assertEqual(Decimal('1.00000001'), result_2)
+
+    def test_from_native_invalid_string(self):
+        """
+        Make sure from_native() raises ValidationError on passing invalid string
+        """
+        f = serializers.DecimalField()
+
+        try:
+            f.from_native('123.45.6')
+        except validators.ValidationError as e:
+            self.assertEqual(e.messages, ["Enter a number."])
+        else:
+            self.fail("ValidationError was not properly raised")
+
+    def test_from_native_integer(self):
+        """
+        Make sure from_native() accepts integer values
+        """
+        f = serializers.DecimalField()
+        result = f.from_native(9000)
+
+        self.assertEqual(Decimal('9000'), result)
+
+    def test_from_native_float(self):
+        """
+        Make sure from_native() accepts float values
+        """
+        f = serializers.DecimalField()
+        result = f.from_native(1.00000001)
+
+        self.assertEqual(Decimal('1.00000001'), result)
+
+    def test_from_native_empty(self):
+        """
+        Make sure from_native() returns None on empty param.
+        """
+        f = serializers.DecimalField()
+        result = f.from_native('')
+
+        self.assertEqual(result, None)
+
+    def test_from_native_none(self):
+        """
+        Make sure from_native() returns None on None param.
+        """
+        f = serializers.DecimalField()
+        result = f.from_native(None)
+
+        self.assertEqual(result, None)
+
+    def test_to_native(self):
+        """
+        Make sure to_native() returns Decimal as string.
+        """
+        f = serializers.DecimalField()
+
+        result_1 = f.to_native(Decimal('9000'))
+        result_2 = f.to_native(Decimal('1.00000001'))
+
+        self.assertEqual('9000', result_1)
+        self.assertEqual('1.00000001', result_2)
+
+    def test_to_native_none(self):
+        """
+        Make sure from_native() returns None on None param.
+        """
+        f = serializers.DecimalField(required=False)
+        self.assertEqual(None, f.to_native(None))
+
+    def test_valid_serialization(self):
+        """
+        Make sure the serializer works correctly
+        """
+        class DecimalSerializer(Serializer):
+            decimal_field = serializers.DecimalField(max_value=9010,
+                                                     min_value=9000,
+                                                     max_digits=6,
+                                                     decimal_places=2)
+
+        self.assertTrue(DecimalSerializer(data={'decimal_field': '9001'}).is_valid())
+        self.assertTrue(DecimalSerializer(data={'decimal_field': '9001.2'}).is_valid())
+        self.assertTrue(DecimalSerializer(data={'decimal_field': '9001.23'}).is_valid())
+
+        self.assertFalse(DecimalSerializer(data={'decimal_field': '8000'}).is_valid())
+        self.assertFalse(DecimalSerializer(data={'decimal_field': '9900'}).is_valid())
+        self.assertFalse(DecimalSerializer(data={'decimal_field': '9001.234'}).is_valid())
+
+    def test_raise_max_value(self):
+        """
+        Make sure max_value violations raises ValidationError
+        """
+        class DecimalSerializer(Serializer):
+            decimal_field = serializers.DecimalField(max_value=100)
+
+        s = DecimalSerializer(data={'decimal_field': '123'})
+
+        self.assertFalse(s.is_valid())
+        self.assertEqual(s.errors,  {'decimal_field': [u'Ensure this value is less than or equal to 100.']})
+
+    def test_raise_min_value(self):
+        """
+        Make sure min_value violations raises ValidationError
+        """
+        class DecimalSerializer(Serializer):
+            decimal_field = serializers.DecimalField(min_value=100)
+
+        s = DecimalSerializer(data={'decimal_field': '99'})
+
+        self.assertFalse(s.is_valid())
+        self.assertEqual(s.errors,  {'decimal_field': [u'Ensure this value is greater than or equal to 100.']})
+
+    def test_raise_max_digits(self):
+        """
+        Make sure max_digits violations raises ValidationError
+        """
+        class DecimalSerializer(Serializer):
+            decimal_field = serializers.DecimalField(max_digits=5)
+
+        s = DecimalSerializer(data={'decimal_field': '123.456'})
+
+        self.assertFalse(s.is_valid())
+        self.assertEqual(s.errors,  {'decimal_field': [u'Ensure that there are no more than 5 digits in total.']})
+
+    def test_raise_max_decimal_places(self):
+        """
+        Make sure max_decimal_places violations raises ValidationError
+        """
+        class DecimalSerializer(Serializer):
+            decimal_field = serializers.DecimalField(decimal_places=3)
+
+        s = DecimalSerializer(data={'decimal_field': '123.4567'})
+
+        self.assertFalse(s.is_valid())
+        self.assertEqual(s.errors,  {'decimal_field': [u'Ensure that there are no more than 3 decimal places.']})
+
+    def test_raise_max_whole_digits(self):
+        """
+        Make sure max_whole_digits violations raises ValidationError
+        """
+        class DecimalSerializer(Serializer):
+            decimal_field = serializers.DecimalField(max_digits=4, decimal_places=3)
+
+        s = DecimalSerializer(data={'decimal_field': '12345.6'})
+
+        self.assertFalse(s.is_valid())
+        self.assertEqual(s.errors,  {'decimal_field': [u'Ensure that there are no more than 4 digits in total.']})
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