Bugfix: Fix run validation layer with invalid data

rest_framework/serializers.py

@@ -315,7 +315,8 @@ class BaseSerializer(WritableField):
         self._errors = {}
         if data is not None or files is not None:
             attrs = self.restore_fields(data, files)
-            attrs = self.perform_validation(attrs)
+            if attrs is not None:
+                attrs = self.perform_validation(attrs)
         else:
             self._errors['non_field_errors'] = ['No input provided']
 

rest_framework/tests/test_validation.py

@@ -63,3 +63,16 @@ class TestPreSaveValidationExclusions(TestCase):
         # does not have `blank=True`, so this serializer should not validate.
         serializer = ShouldValidateModelSerializer(data={'renamed': ''})
         self.assertEqual(serializer.is_valid(), False)
+
+
+class FieldValidationSerializer(serializers.Serializer):
+    foo = serializers.CharField()
+
+    def validate_foo(self, attrs, source):
+        raise StandardError("validate_foo was called")
+
+
+class TestFieldValidationWithInvalidData(TestCase):
+    def test_validate_foo_was_not_called(self):
+        serializer = FieldValidationSerializer(data='invalid data')
+        self.assertFalse(serializer.is_valid())