Fix raising on nullable fields part of UniqueConstraint

tests/test_model_serializer.py

@@ -542,6 +542,15 @@ class Meta:
         unique_together = ("foreign_key", "one_to_one")
 
 
+class NullableUniqueTogetherModel(models.Model):
+    name = models.CharField(max_length=100)
+    field_1 = models.IntegerField(null=True)
+    field_2 = models.TextField(null=True)
+
+    class Meta:
+        unique_together = ("field_1", "field_2")
+
+
 class TestRelationalFieldMappings(TestCase):
     def test_pk_relations(self):
         class TestSerializer(serializers.ModelSerializer):
@@ -731,6 +740,17 @@ class Meta:
         """)
         self.assertEqual(repr(TestSerializer()), expected)
 
+    def test_nullable_unique_together(self):
+        class TestSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = NullableUniqueTogetherModel
+                fields = ('name', 'field_1', 'field_2')
+
+        serializer = TestSerializer(data={"name": "Test"})
+        self.assertTrue(serializer.is_valid(), serializer.errors)
+        instance = serializer.save()
+        assert isinstance(instance, NullableUniqueTogetherModel)
+
 
 class DisplayValueTargetModel(models.Model):
     name = models.CharField(max_length=100)
@@ -1400,3 +1420,28 @@ class Meta:
         serializer.save()
 
         self.assertEqual(instance.char_field, 'value changed by signal')
+
+
+class UniqueConstraintNullableModel(models.Model):
+    title = models.CharField(max_length=100)
+    age = models.IntegerField(null=True)
+    tag = models.CharField(max_length=100, null=True)
+
+    class Meta:
+        constraints = [
+            # Unique constraint on 2 nullable fields
+            models.UniqueConstraint(name='unique_constraint', fields=('age', 'tag'))
+        ]
+
+
+class TestUniqueConstraintWithNullableFields(TestCase):
+    def test_nullable_unique_constraint_fields_are_not_required(self):
+        class UniqueConstraintNullableSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = UniqueConstraintNullableModel
+                fields = ('title', 'age', 'tag')
+
+        serializer = UniqueConstraintNullableSerializer(data={'title': 'Bob'})
+        self.assertTrue(serializer.is_valid(), serializer.errors)
+        result = serializer.save()
+        self.assertIsInstance(result, UniqueConstraintNullableModel)

tests/test_validators.py

@@ -441,6 +441,14 @@ def test_ignore_validation_for_null_fields(self):
         serializer = NullUniquenessTogetherSerializer(data=data)
         assert serializer.is_valid()
 
+    def test_ignore_validation_for_missing_nullable_fields(self):
+        data = {
+            'date': datetime.date(2000, 1, 1),
+            'race_name': 'Paris Marathon',
+        }
+        serializer = NullUniquenessTogetherSerializer(data=data)
+        assert serializer.is_valid(), serializer.errors
+
     def test_do_not_ignore_validation_for_null_fields(self):
         # None values that are not on fields part of the uniqueness constraint
         # do not cause the instance to skip validation.