update way to extract m2m fields on bulk lists

backend/metagenedb/apps/catalog/serializers/bulk_list.py

+from collections import defaultdict
+
 from rest_framework import serializers
 from rest_framework.exceptions import ValidationError, ErrorDetail
 from rest_framework.fields import SkipField
@@ -7,13 +9,20 @@ from rest_framework.utils import html, model_meta
 
 class BulkListSerializer(serializers.ListSerializer):
 
-    def _extract_many_to_many(self, validated_data, info):
-        many_to_many = [{} for v in validated_data]
+    def _extract_many_to_many(self, validated_data, info, lookup_field):
+        many_to_many = {
+            'keys': set(),
+            'values': defaultdict(list)
+        }
         for field_name, relation_info in info.relations.items():
             if relation_info.to_many:
-                for data_item, many_to_many_item in zip(validated_data, many_to_many):
+                for data_item in validated_data:
                     if field_name in data_item:
-                        many_to_many_item[field_name] = data_item.pop(field_name)
+                        many_to_many['keys'].add(field_name)
+                        many_to_many['values'][field_name].append({
+                            field_name: data_item.pop(field_name),
+                            lookup_field: data_item[lookup_field]
+                        })
         return many_to_many
 
     def _get_db_index_fields(self, info):
@@ -93,9 +102,15 @@ class BulkListSerializer(serializers.ListSerializer):
 
     def create(self, validated_data):
         ModelClass = self.Meta.model
+        info = model_meta.get_field_info(ModelClass)
+        lookup_field = self._get_db_index_fields(info)[0]
+        many_to_many = self._extract_many_to_many(validated_data, info, lookup_field)
         instances = ModelClass.objects.bulk_create(
             [ModelClass(**item) for item in validated_data]
         )
+        if many_to_many:
+            for field in many_to_many['keys']:
+                getattr(self, f'_handle_{field}', None)(many_to_many['values'][field])
         return instances
 
     def update(self, instances, validated_data):
@@ -105,8 +120,8 @@ class BulkListSerializer(serializers.ListSerializer):
         """
         ModelClass = self.Meta.model
         info = model_meta.get_field_info(ModelClass)
-        db_index_fields = self._get_db_index_fields(info)
-        lookup_field = db_index_fields[0]
+        lookup_field = self._get_db_index_fields(info)[0]
+        many_to_many = self._extract_many_to_many(validated_data, info, lookup_field)
         updated_keys = self._get_all_key_fields(validated_data)
         validated_data = {item.pop(lookup_field): item for item in validated_data}
         for item_id, validated_data_element in validated_data.items():
@@ -116,6 +131,10 @@ class BulkListSerializer(serializers.ListSerializer):
             list(instances.values()),
             updated_keys
         )
+        # Link existing many-to-many relationships.
+        if many_to_many:
+            for field in many_to_many['keys']:
+                getattr(self, f'_handle_{field}', None)(many_to_many['values'][field])
         return list(instances.values())
 
     class Meta:

backend/metagenedb/apps/catalog/serializers/test_bulk_list.py

@@ -24,8 +24,8 @@ class BaseTestBulkListSerializerMethods(TestCase):
 
     def setUp(self):
         self.data = [
-            {'field1': 'value1', 'field2': 'value2'},
-            {'field1': 'value3', 'field2': 'value4'}
+            {'id': 'entry_1', 'field1': 'value1', 'field2': 'value2'},
+            {'id': 'entry_2', 'field1': 'value3', 'field2': 'value4'}
         ]
         self.bulk_list_serializer = BulkListSerializerTestExtractManyToMany()
         self.info = Mock()
@@ -39,12 +39,17 @@ class TestExtractManyToMany(BaseTestBulkListSerializerMethods):
             'field2': Mock(to_many=False)
         }
         ori_list = deepcopy(self.data)
-        expected_list = [
-            {'field1': 'value1'},
-            {'field1': 'value3'}
-        ]
-        tested_list = self.bulk_list_serializer._extract_many_to_many(self.data, self.info)
-        self.assertListEqual(tested_list, expected_list)
+        expected_dict = {
+            'keys': {'field1'},
+            'values': {
+                'field1': [
+                    {'field1': 'value1', 'id': 'entry_1'},
+                    {'field1': 'value3', 'id': 'entry_2'}
+                ]
+            }
+        }
+        tested_dict = self.bulk_list_serializer._extract_many_to_many(self.data, self.info, 'id')
+        self.assertDictEqual(tested_dict, expected_dict)
         self.assertNotEqual(ori_list, self.data)
 
     def test_extract_no_many_to_many(self):
@@ -53,12 +58,12 @@ class TestExtractManyToMany(BaseTestBulkListSerializerMethods):
             'field2': Mock(to_many=False)
         }
         ori_list = deepcopy(self.data)
-        expected_list = [
-            {},
-            {}
-        ]
-        tested_list = self.bulk_list_serializer._extract_many_to_many(self.data, self.info)
-        self.assertListEqual(tested_list, expected_list)
+        expected_dict = {
+            'keys': set(),
+            'values': {}
+        }
+        tested_dict = self.bulk_list_serializer._extract_many_to_many(self.data, self.info, 'id')
+        self.assertDictEqual(tested_dict, expected_dict)
         self.assertListEqual(ori_list, self.data)