Handle duplicated manual classification creation

arkindex/documents/api/ml.py

@@ -170,6 +170,14 @@ class ClassificationCreate(CreateAPIView):
                 'internal': False,
             }
         )
+        if Classification.objects.filter(
+            element_id=serializer.validated_data['element'],
+            source_id=data_source.id,
+            ml_class_id=serializer.validated_data['ml_class']
+        ).exists():
+            raise ValidationError(
+                {'__all__': ['A manual classification already exists for this `element` and this `class`']}
+            )
         serializer.save(
             source=data_source,
             moderator=self.request.user,

arkindex/documents/tests/test_moderation.py

@@ -40,6 +40,27 @@ class TestClasses(FixtureAPITestCase):
         self.assertEqual(response.data['confidence'], 1)
         self.assertEqual(response.data['best'], True)
 
+    def test_classification_exists(self):
+        """
+        If a classification exists, creation must respond a 400_BAD_REQUEST
+        with an explicit message
+        """
+        self.client.force_login(self.user)
+        request = (
+            reverse('api:classification-create'),
+            {
+                'element': str(self.element.id),
+                'ml_class': str(self.text.id)
+            }
+        )
+        response = self.client.post(*request)
+        self.assertEqual(response.status_code, status.HTTP_201_CREATED)
+        response = self.client.post(*request)
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertDictEqual(response.json(), {
+            '__all__': ['A manual classification already exists for this `element` and this `class`']
+        })
+
     def test_classification_ignored_params(self):
         """
         Ensure confidence and best attribute  cannot be changed