Add compat util for DecimalValidator

rest_framework/compat.py

@@ -185,6 +185,11 @@ def apply_markdown(text):
 else:
     DurationField = duration_string = parse_duration = None
 
+try:
+    # DecimalValidator is unavailable in Django < 1.9
+    from django.core.validators import DecimalValidator
+except ImportError:
+    DecimalValidator = None
 
 def set_rollback():
     if hasattr(transaction, 'set_rollback'):

rest_framework/utils/field_mapping.py

@@ -8,6 +8,7 @@
 from django.db import models
 from django.utils.text import capfirst
 
+from rest_framework.compat import DecimalValidator
 from rest_framework.validators import UniqueValidator
 
 NUMERIC_FIELD_TYPES = (
@@ -132,7 +133,7 @@ def get_field_kwargs(field_name, model_field):
     if isinstance(model_field, models.DecimalField):
         validator_kwarg = [
             validator for validator in validator_kwarg
-            if not isinstance(validator, validators.DecimalValidator)
+            if DecimalValidator and not isinstance(validator, DecimalValidator)
         ]
 
     # Ensure that max_length is passed explicitly as a keyword arg,

tests/test_model_serializer.py

@@ -22,7 +22,7 @@
 
 from rest_framework import serializers
 from rest_framework.compat import DurationField as ModelDurationField
-from rest_framework.compat import unicode_repr
+from rest_framework.compat import DecimalValidator, unicode_repr
 
 
 def dedent(blocktext):
@@ -861,3 +861,41 @@ class Meta:
         }]
 
         assert serializer.data == expected
+
+
+class DecimalFieldModel(models.Model):
+    decimal_field = models.DecimalField(
+        max_digits=3,
+        decimal_places=1,
+        validators=[MinValueValidator(1), MaxValueValidator(3)]
+    )
+
+
+class TestDecimalFieldMappings(TestCase):
+    @pytest.mark.skipif(DecimalValidator is not None,
+                        reason='DecimalValidator is available in Django 1.9+')
+    def test_decimal_field_has_no_decimal_validator(self):
+        """
+        Test that a DecimalField has no validators before Django 1.9.
+        """
+        class TestSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = DecimalFieldModel
+
+        serializer = TestSerializer()
+
+        assert len(serializer.fields['decimal_field'].validators) == 0
+
+    @pytest.mark.skipif(DecimalValidator is None,
+                        reason='DecimalValidator is available in Django 1.9+')
+    def test_decimal_field_has_decimal_validator(self):
+        """
+        Test that a DecimalField has DecimalValidator in Django 1.9+.
+        """
+        class TestSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = DecimalFieldModel
+
+        serializer = TestSerializer()
+
+        assert len(serializer.fields['decimal_field'].validators) == 2