Uniqueness constraints imply a forced 'required=True'. Refs #1945

docs/api-guide/validators.md

@@ -93,6 +93,12 @@ The validator should be applied to *serializer classes*, like so:
                 )
             ]
 
+---
+
+**Note**: The `UniqueTogetherValidation` class always imposes an implicit constraint that all the fields it applies to are always treated as required. Fields with `default` values are an exception to this as they always supply a value even when omitted from user input.
+
+---
+
 ## UniqueForDateValidator
 
 ## UniqueForMonthValidator
@@ -146,6 +152,10 @@ If you want the date field to be entirely hidden from the user, then use `Hidden
 
 ---
 
+**Note**: The `UniqueFor<Range>Validation` classes always imposes an implicit constraint that the fields they are applied to are always treated as required. Fields with `default` values are an exception to this as they always supply a value even when omitted from user input.
+
+---
+
 # Writing custom validators
 
 You can use any of Django's existing validators, or write your own custom validators.

rest_framework/validators.py

@@ -25,6 +25,10 @@ class UniqueValidator:
         self.message = message or self.message
 
     def set_context(self, serializer_field):
+        """
+        This hook is called by the serializer instance,
+        prior to the validation call being made.
+        """
         # Determine the underlying model field name. This may not be the
         # same as the serializer field name if `source=<>` is set.
         self.field_name = serializer_field.source_attrs[0]
@@ -54,6 +58,7 @@ class UniqueTogetherValidator:
     Should be applied to the serializer class, not to an individual field.
     """
     message = _('The fields {field_names} must make a unique set.')
+    missing_message = _('This field is required.')
 
     def __init__(self, queryset, fields, message=None):
         self.queryset = queryset
@@ -62,17 +67,49 @@ class UniqueTogetherValidator:
         self.message = message or self.message
 
     def set_context(self, serializer):
+        """
+        This hook is called by the serializer instance,
+        prior to the validation call being made.
+        """
         # Determine the existing instance, if this is an update operation.
         self.instance = getattr(serializer, 'instance', None)
 
-    def __call__(self, attrs):
-        # Ensure uniqueness.
+    def enforce_required_fields(self, attrs):
+        """
+        The `UniqueTogetherValidator` always forces an implied 'required'
+        state on the fields it applies to.
+        """
+        missing = dict([
+            (field_name, self.missing_message)
+            for field_name in self.fields
+            if field_name not in attrs
+        ])
+        if missing:
+            raise ValidationError(missing)
+
+    def filter_queryset(self, attrs, queryset):
+        """
+        Filter the queryset to all instances matching the given attributes.
+        """
         filter_kwargs = dict([
             (field_name, attrs[field_name]) for field_name in self.fields
         ])
-        queryset = self.queryset.filter(**filter_kwargs)
+        return queryset.filter(**filter_kwargs)
+
+    def exclude_current_instance(self, attrs, queryset):
+        """
+        If an instance is being updated, then do not include
+        that instance itself as a uniqueness conflict.
+        """
         if self.instance is not None:
-            queryset = queryset.exclude(pk=self.instance.pk)
+            return queryset.exclude(pk=self.instance.pk)
+        return queryset
+
+    def __call__(self, attrs):
+        self.enforce_required_fields(attrs)
+        queryset = self.queryset
+        queryset = self.filter_queryset(attrs, queryset)
+        queryset = self.exclude_current_instance(attrs, queryset)
         if queryset.exists():
             field_names = ', '.join(self.fields)
             raise ValidationError(self.message.format(field_names=field_names))
@@ -87,6 +124,7 @@ class UniqueTogetherValidator:
 
 class BaseUniqueForValidator:
     message = None
+    missing_message = _('This field is required.')
 
     def __init__(self, queryset, field, date_field, message=None):
         self.queryset = queryset
@@ -95,6 +133,10 @@ class BaseUniqueForValidator:
         self.message = message or self.message
 
     def set_context(self, serializer):
+        """
+        This hook is called by the serializer instance,
+        prior to the validation call being made.
+        """
         # Determine the underlying model field names. These may not be the
         # same as the serializer field names if `source=<>` is set.
         self.field_name = serializer.fields[self.field].source_attrs[0]
@@ -102,15 +144,36 @@ class BaseUniqueForValidator:
         # Determine the existing instance, if this is an update operation.
         self.instance = getattr(serializer, 'instance', None)
 
-    def get_filter_kwargs(self, attrs):
-        raise NotImplementedError('`get_filter_kwargs` must be implemented.')
+    def enforce_required_fields(self, attrs):
+        """
+        The `UniqueFor<Range>Validator` classes always force an implied
+        'required' state on the fields they are applied to.
+        """
+        missing = dict([
+            (field_name, self.missing_message)
+            for field_name in [self.field, self.date_field]
+            if field_name not in attrs
+        ])
+        if missing:
+            raise ValidationError(missing)
+
+    def filter_queryset(self, attrs, queryset):
+        raise NotImplementedError('`filter_queryset` must be implemented.')
+
+    def exclude_current_instance(self, attrs, queryset):
+        """
+        If an instance is being updated, then do not include
+        that instance itself as a uniqueness conflict.
+        """
+        if self.instance is not None:
+            return queryset.exclude(pk=self.instance.pk)
+        return queryset
 
     def __call__(self, attrs):
-        filter_kwargs = self.get_filter_kwargs(attrs)
-
-        queryset = self.queryset.filter(**filter_kwargs)
-        if self.instance is not None:
-            queryset = queryset.exclude(pk=self.instance.pk)
+        self.enforce_required_fields(attrs)
+        queryset = self.queryset
+        queryset = self.filter_queryset(attrs, queryset)
+        queryset = self.exclude_current_instance(attrs, queryset)
         if queryset.exists():
             message = self.message.format(date_field=self.date_field)
             raise ValidationError({self.field: message})
@@ -127,7 +190,7 @@ class BaseUniqueForValidator:
 class UniqueForDateValidator(BaseUniqueForValidator):
     message = _('This field must be unique for the "{date_field}" date.')
 
-    def get_filter_kwargs(self, attrs):
+    def filter_queryset(self, attrs, queryset):
         value = attrs[self.field]
         date = attrs[self.date_field]
 
@@ -136,30 +199,30 @@ 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 filter_kwargs
+        return queryset.filter(**filter_kwargs)
 
 
 class UniqueForMonthValidator(BaseUniqueForValidator):
     message = _('This field must be unique for the "{date_field}" month.')
 
-    def get_filter_kwargs(self, attrs):
+    def filter_queryset(self, attrs, queryset):
         value = attrs[self.field]
         date = attrs[self.date_field]
 
         filter_kwargs = {}
         filter_kwargs[self.field_name] = value
         filter_kwargs['%s__month' % self.date_field_name] = date.month
-        return filter_kwargs
+        return queryset.filter(**filter_kwargs)
 
 
 class UniqueForYearValidator(BaseUniqueForValidator):
     message = _('This field must be unique for the "{date_field}" year.')
 
-    def get_filter_kwargs(self, attrs):
+    def filter_queryset(self, attrs, queryset):
         value = attrs[self.field]
         date = attrs[self.date_field]
 
         filter_kwargs = {}
         filter_kwargs[self.field_name] = value
         filter_kwargs['%s__year' % self.date_field_name] = date.year
-        return filter_kwargs
+        return queryset.filter(**filter_kwargs)

tests/test_validators.py

@@ -134,6 +134,17 @@ class TestUniquenessTogetherValidation(TestCase):
             'position': 1
         }
 
+    def test_unique_together_is_required(self):
+        """
+        In a unique together validation, all fields are required.
+        """
+        data = {'position': 2}
+        serializer = UniquenessTogetherSerializer(data=data, partial=True)
+        assert not serializer.is_valid()
+        assert serializer.errors == {
+            'race_name': ['This field is required.']
+        }
+
     def test_ignore_excluded_fields(self):
         """
         When model fields are not included in a serializer, then uniqueness