Fix regression in unique_together validation with SerializerMethodField

rest_framework/serializers.py

@@ -1469,12 +1469,13 @@ def get_uniqueness_extra_kwargs(self, field_names, declared_fields, extra_kwargs
                                         model_field.unique_for_year}
 
         unique_constraint_names -= {None}
+        model_fields_names = set(model_fields.keys())
 
         # Include each of the `unique_together` and `UniqueConstraint` field names,
         # so long as all the field names are included on the serializer.
         for unique_together_list, queryset, condition_fields, condition in self.get_unique_together_constraints(model):
             unique_together_list_and_condition_fields = set(unique_together_list) | set(condition_fields)
-            if set(field_names).issuperset(unique_together_list_and_condition_fields):
+            if model_fields_names.issuperset(unique_together_list_and_condition_fields):
                 unique_constraint_names |= unique_together_list_and_condition_fields
 
         # Now we have all the field names that have uniqueness constraints

tests/test_validators.py

@@ -516,6 +516,43 @@ def filter(self, **kwargs):
         validator.filter_queryset(attrs=data, queryset=queryset, serializer=serializer)
         assert queryset.called_with == {'race_name': 'bar', 'position': 1}
 
+    def test_uniq_together_validation_uses_model_fields_method_field(self):
+        class TestSerializer(serializers.ModelSerializer):
+            position = serializers.SerializerMethodField()
+
+            def get_position(self, obj):
+                return obj.position or 0
+
+            class Meta:
+                model = NullUniquenessTogetherModel
+                fields = ['race_name', 'position']
+
+        serializer = TestSerializer()
+        expected = dedent("""
+            TestSerializer():
+                race_name = CharField(max_length=100)
+                position = SerializerMethodField()
+        """)
+        assert repr(serializer) == expected
+
+    def test_uniq_together_validation_uses_model_fields_with_source_field(self):
+        class TestSerializer(serializers.ModelSerializer):
+            pos = serializers.IntegerField(source='position')
+
+            class Meta:
+                model = NullUniquenessTogetherModel
+                fields = ['race_name', 'pos']
+
+        serializer = TestSerializer()
+        expected = dedent("""
+            TestSerializer():
+                race_name = CharField(max_length=100, required=True)
+                pos = IntegerField(source='position')
+                class Meta:
+                    validators = [<UniqueTogetherValidator(queryset=NullUniquenessTogetherModel.objects.all(), fields=('race_name', 'pos'))>]
+        """)
+        assert repr(serializer) == expected
+
 
 class UniqueConstraintModel(models.Model):
     race_name = models.CharField(max_length=100)