Robust uniqueness checks. (#4217)

* Robust uniqueness checks
* Add master to test matrix (allow_failures)

.travis.yml

@@ -19,13 +19,16 @@ env:
     - TOX_ENV=py27-django110
     - TOX_ENV=py35-django110
     - TOX_ENV=py34-django110
+    - TOX_ENV=py27-djangomaster
+    - TOX_ENV=py34-djangomaster
+    - TOX_ENV=py35-djangomaster
 
 matrix:
     fast_finish: true
     allow_failures:
-      - TOX_ENV=py27-djangomaster
-      - TOX_ENV=py34-djangomaster
-      - TOX_ENV=py35-djangomaster
+      - env: TOX_ENV=py27-djangomaster
+      - env: TOX_ENV=py34-djangomaster
+      - env: TOX_ENV=py35-djangomaster
 
 install:
     # Virtualenv < 14 is required to keep the Python 3.2 builds running.

rest_framework/validators.py

@@ -8,6 +8,7 @@ object creation, and makes it possible to switch between using the implicit
 """
 from __future__ import unicode_literals
 
+from django.db import DataError
 from django.utils.translation import ugettext_lazy as _
 
 from rest_framework.compat import unicode_to_repr
@@ -15,6 +16,24 @@ from rest_framework.exceptions import ValidationError
 from rest_framework.utils.representation import smart_repr
 
 
+# Robust filter and exist implementations. Ensures that queryset.exists() for
+# an invalid value returns `False`, rather than raising an error.
+# Refs https://github.com/tomchristie/django-rest-framework/issues/3381
+
+def qs_exists(queryset):
+    try:
+        return queryset.exists()
+    except (TypeError, ValueError, DataError):
+        return False
+
+
+def qs_filter(queryset, **kwargs):
+    try:
+        return queryset.filter(**kwargs)
+    except (TypeError, ValueError, DataError):
+        return queryset.none()
+
+
 class UniqueValidator(object):
     """
     Validator that corresponds to `unique=True` on a model field.
@@ -44,7 +63,7 @@ class UniqueValidator(object):
         Filter the queryset to all instances matching the given attribute.
         """
         filter_kwargs = {self.field_name: value}
-        return queryset.filter(**filter_kwargs)
+        return qs_filter(queryset, **filter_kwargs)
 
     def exclude_current_instance(self, queryset):
         """
@@ -59,7 +78,7 @@ class UniqueValidator(object):
         queryset = self.queryset
         queryset = self.filter_queryset(value, queryset)
         queryset = self.exclude_current_instance(queryset)
-        if queryset.exists():
+        if qs_exists(queryset):
             raise ValidationError(self.message)
 
     def __repr__(self):
@@ -124,7 +143,7 @@ class UniqueTogetherValidator(object):
             field_name: attrs[field_name]
             for field_name in self.fields
         }
-        return queryset.filter(**filter_kwargs)
+        return qs_filter(queryset, **filter_kwargs)
 
     def exclude_current_instance(self, attrs, queryset):
         """
@@ -145,7 +164,7 @@ class UniqueTogetherValidator(object):
         checked_values = [
             value for field, value in attrs.items() if field in self.fields
         ]
-        if None not in checked_values and queryset.exists():
+        if None not in checked_values and qs_exists(queryset):
             field_names = ', '.join(self.fields)
             raise ValidationError(self.message.format(field_names=field_names))
 
@@ -209,7 +228,7 @@ class BaseUniqueForValidator(object):
         queryset = self.queryset
         queryset = self.filter_queryset(attrs, queryset)
         queryset = self.exclude_current_instance(attrs, queryset)
-        if queryset.exists():
+        if qs_exists(queryset):
             message = self.message.format(date_field=self.date_field)
             raise ValidationError({self.field: message})
 
@@ -234,7 +253,7 @@ class UniqueForDateValidator(BaseUniqueForValidator):
         filter_kwargs['%s__day' % self.date_field_name] = date.day
         filter_kwargs['%s__month' % self.date_field_name] = date.month
         filter_kwargs['%s__year' % self.date_field_name] = date.year
-        return queryset.filter(**filter_kwargs)
+        return qs_filter(queryset, **filter_kwargs)
 
 
 class UniqueForMonthValidator(BaseUniqueForValidator):
@@ -247,7 +266,7 @@ class UniqueForMonthValidator(BaseUniqueForValidator):
         filter_kwargs = {}
         filter_kwargs[self.field_name] = value
         filter_kwargs['%s__month' % self.date_field_name] = date.month
-        return queryset.filter(**filter_kwargs)
+        return qs_filter(queryset, **filter_kwargs)
 
 
 class UniqueForYearValidator(BaseUniqueForValidator):
@@ -260,4 +279,4 @@ class UniqueForYearValidator(BaseUniqueForValidator):
         filter_kwargs = {}
         filter_kwargs[self.field_name] = value
         filter_kwargs['%s__year' % self.date_field_name] = date.year
-        return queryset.filter(**filter_kwargs)
+        return qs_filter(queryset, **filter_kwargs)

tests/test_validators.py

@@ -48,6 +48,18 @@ class AnotherUniquenessSerializer(serializers.ModelSerializer):
         fields = '__all__'
 
 
+class IntegerFieldModel(models.Model):
+    integer = models.IntegerField()
+
+
+class UniquenessIntegerSerializer(serializers.Serializer):
+    # Note that this field *deliberately* does not correspond with the model field.
+    # This allows us to ensure that `ValueError`, `TypeError` or `DataError` etc
+    # raised by a uniqueness check does not trigger a deceptive "this field is not unique"
+    # validation failure.
+    integer = serializers.CharField(validators=[UniqueValidator(queryset=IntegerFieldModel.objects.all())])
+
+
 class TestUniquenessValidation(TestCase):
     def setUp(self):
         self.instance = UniquenessModel.objects.create(username='existing')
@@ -100,6 +112,10 @@ class TestUniquenessValidation(TestCase):
         rs = RelatedModelSerializer(data=data)
         self.assertTrue(rs.is_valid())
 
+    def test_value_error_treated_as_not_unique(self):
+        serializer = UniquenessIntegerSerializer(data={'integer': 'abc'})
+        assert serializer.is_valid()
+
 
 # Tests for `UniqueTogetherValidator`
 # -----------------------------------