Primary Support of UniqueConstraint

rest_framework/serializers.py

@@ -1398,6 +1398,23 @@ def get_extra_kwargs(self):
 
         return extra_kwargs
 
+    def get_unique_together_constraints(self, model):
+        """
+        Returns iterator of (fields, queryset), each entry describes an unique together
+        constraint on `fields` in `queryset`.
+        """
+        for parent_class in [model] + list(model._meta.parents):
+            for unique_together in parent_class._meta.unique_together:
+                yield unique_together, model._default_manager
+            for constraint in parent_class._meta.constraints:
+                if isinstance(constraint, models.UniqueConstraint) and len(constraint.fields) > 1:
+                    yield (
+                        constraint.fields,
+                        model._default_manager
+                        if constraint.condition is None
+                        else model._default_manager.filter(constraint.condition)
+                    )
+
     def get_uniqueness_extra_kwargs(self, field_names, declared_fields, extra_kwargs):
         """
         Return any additional field options that need to be included as a
@@ -1426,12 +1443,11 @@ def get_uniqueness_extra_kwargs(self, field_names, declared_fields, extra_kwargs
 
         unique_constraint_names -= {None}
 
-        # Include each of the `unique_together` field names,
+        # Include each of the `unique_together` and `UniqueConstraint` field names,
         # so long as all the field names are included on the serializer.
-        for parent_class in [model] + list(model._meta.parents):
-            for unique_together_list in parent_class._meta.unique_together:
-                if set(field_names).issuperset(unique_together_list):
-                    unique_constraint_names |= set(unique_together_list)
+        for unique_together_list, queryset in self.get_unique_together_constraints(model):
+            if set(field_names).issuperset(unique_together_list):
+                unique_constraint_names |= set(unique_together_list)
 
         # Now we have all the field names that have uniqueness constraints
         # applied, we can add the extra 'required=...' or 'default=...'
@@ -1526,11 +1542,6 @@ def get_unique_together_validators(self):
         """
         Determine a default set of validators for any unique_together constraints.
         """
-        model_class_inheritance_tree = (
-            [self.Meta.model] +
-            list(self.Meta.model._meta.parents)
-        )
-
         # The field names we're passing though here only include fields
         # which may map onto a model field. Any dotted field name lookups
         # cannot map to a field, and must be a traversal, so we're not
@@ -1556,34 +1567,33 @@ def get_unique_together_validators(self):
         # Note that we make sure to check `unique_together` both on the
         # base model class, but also on any parent classes.
         validators = []
-        for parent_class in model_class_inheritance_tree:
-            for unique_together in parent_class._meta.unique_together:
-                # Skip if serializer does not map to all unique together sources
-                if not set(source_map).issuperset(unique_together):
-                    continue
-
-                for source in unique_together:
-                    assert len(source_map[source]) == 1, (
-                        "Unable to create `UniqueTogetherValidator` for "
-                        "`{model}.{field}` as `{serializer}` has multiple "
-                        "fields ({fields}) that map to this model field. "
-                        "Either remove the extra fields, or override "
-                        "`Meta.validators` with a `UniqueTogetherValidator` "
-                        "using the desired field names."
-                        .format(
-                            model=self.Meta.model.__name__,
-                            serializer=self.__class__.__name__,
-                            field=source,
-                            fields=', '.join(source_map[source]),
-                        )
-                    )
+        for unique_together, queryset in self.get_unique_together_constraints(self.Meta.model):
+            # Skip if serializer does not map to all unique together sources
+            if not set(source_map).issuperset(unique_together):
+                continue
 
-                field_names = tuple(source_map[f][0] for f in unique_together)
-                validator = UniqueTogetherValidator(
-                    queryset=parent_class._default_manager,
-                    fields=field_names
+            for source in unique_together:
+                assert len(source_map[source]) == 1, (
+                    "Unable to create `UniqueTogetherValidator` for "
+                    "`{model}.{field}` as `{serializer}` has multiple "
+                    "fields ({fields}) that map to this model field. "
+                    "Either remove the extra fields, or override "
+                    "`Meta.validators` with a `UniqueTogetherValidator` "
+                    "using the desired field names."
+                    .format(
+                        model=self.Meta.model.__name__,
+                        serializer=self.__class__.__name__,
+                        field=source,
+                        fields=', '.join(source_map[source]),
+                    )
                 )
-                validators.append(validator)
+
+            field_names = tuple(source_map[f][0] for f in unique_together)
+            validator = UniqueTogetherValidator(
+                queryset=queryset,
+                fields=field_names
+            )
+            validators.append(validator)
         return validators
 
     def get_unique_for_date_validators(self):

rest_framework/utils/field_mapping.py

@@ -62,6 +62,29 @@ def get_detail_view_name(model):
     }
 
 
+def get_unique_validators(field_name, model_field):
+    """
+    Returns a list of UniqueValidators that should be applied to the field.
+    """
+    field_set = set([field_name])
+    conditions = {
+        c.condition
+        for c in model_field.model._meta.constraints
+        if isinstance(c, models.UniqueConstraint) and set(c.fields) == field_set
+    }
+    if getattr(model_field, 'unique', False):
+        conditions.add(None)
+    if not conditions:
+        return
+    unique_error_message = get_unique_error_message(model_field)
+    queryset = model_field.model._default_manager
+    for condition in conditions:
+        yield UniqueValidator(
+            queryset=queryset if condition is None else queryset.filter(condition),
+            message=unique_error_message
+        )
+
+
 def get_field_kwargs(field_name, model_field):
     """
     Creates a default instance of a basic non-relational field.
@@ -216,11 +239,7 @@ def get_field_kwargs(field_name, model_field):
             if not isinstance(validator, validators.MinLengthValidator)
         ]
 
-    if getattr(model_field, 'unique', False):
-        validator = UniqueValidator(
-            queryset=model_field.model._default_manager,
-            message=get_unique_error_message(model_field))
-        validator_kwarg.append(validator)
+    validator_kwarg += get_unique_validators(field_name, model_field)
 
     if validator_kwarg:
         kwargs['validators'] = validator_kwarg

tests/test_validators.py

@@ -464,6 +464,106 @@ def filter(self, **kwargs):
         assert queryset.called_with == {'race_name': 'bar', 'position': 1}
 
 
+class UniqueConstraintModel(models.Model):
+    race_name = models.CharField(max_length=100)
+    position = models.IntegerField()
+    global_id = models.IntegerField()
+    fancy_conditions = models.IntegerField(null=True)
+
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(
+                name="unique_constraint_model_global_id_uniq",
+                fields=('global_id',),
+            ),
+            models.UniqueConstraint(
+                name="unique_constraint_model_fancy_1_uniq",
+                fields=('fancy_conditions',),
+                condition=models.Q(global_id__lte=1)
+            ),
+            models.UniqueConstraint(
+                name="unique_constraint_model_fancy_3_uniq",
+                fields=('fancy_conditions',),
+                condition=models.Q(global_id__gte=3)
+            ),
+            models.UniqueConstraint(
+                name="unique_constraint_model_together_uniq",
+                fields=('race_name', 'position'),
+                condition=models.Q(race_name='example'),
+            )
+        ]
+
+
+class UniqueConstraintSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = UniqueConstraintModel
+        fields = '__all__'
+
+
+class TestUniqueConstraintValidation(TestCase):
+    def setUp(self):
+        self.instance = UniqueConstraintModel.objects.create(
+            race_name='example',
+            position=1,
+            global_id=1
+        )
+        UniqueConstraintModel.objects.create(
+            race_name='example',
+            position=2,
+            global_id=2
+        )
+        UniqueConstraintModel.objects.create(
+            race_name='other',
+            position=1,
+            global_id=3
+        )
+
+    def test_repr(self):
+        serializer = UniqueConstraintSerializer()
+        # the order of validators isn't deterministic so delete
+        # fancy_conditions field that has two of them
+        del serializer.fields['fancy_conditions']
+        expected = dedent("""
+            UniqueConstraintSerializer():
+                id = IntegerField(label='ID', read_only=True)
+                race_name = CharField(max_length=100, required=True)
+                position = IntegerField(required=True)
+                global_id = IntegerField(validators=[<UniqueValidator(queryset=UniqueConstraintModel.objects.all())>])
+                class Meta:
+                    validators = [<UniqueTogetherValidator(queryset=<QuerySet [<UniqueConstraintModel: UniqueConstraintModel object (1)>, <UniqueConstraintModel: UniqueConstraintModel object (2)>]>, fields=('race_name', 'position'))>]
+        """)
+        assert repr(serializer) == expected
+
+    def test_unique_together_field(self):
+        """
+        UniqueConstraint fields and condition attributes must be passed
+        to UniqueTogetherValidator as fields and queryset
+        """
+        serializer = UniqueConstraintSerializer()
+        assert len(serializer.validators) == 1
+        validator = serializer.validators[0]
+        assert validator.fields == ('race_name', 'position')
+        assert set(validator.queryset.values_list(flat=True)) == set(
+            UniqueConstraintModel.objects.filter(race_name='example').values_list(flat=True)
+        )
+
+    def test_single_field_uniq_validators(self):
+        """
+        UniqueConstraint with single field must be transformed into
+        field's UniqueValidator
+        """
+        serializer = UniqueConstraintSerializer()
+        assert len(serializer.validators) == 1
+        validators = serializer.fields['global_id'].validators
+        assert len(validators) == 1
+        assert validators[0].queryset == UniqueConstraintModel.objects
+
+        validators = serializer.fields['fancy_conditions'].validators
+        assert len(validators) == 2
+        ids_in_qs = {frozenset(v.queryset.values_list(flat=True)) for v in validators}
+        assert ids_in_qs == {frozenset([1]), frozenset([3])}
+
+
 # Tests for `UniqueForDateValidator`
 # ----------------------------------