fix: Make the instance variable of child serializer point to the correct list object instead of the entire list when validating ListSerializer

tests/test_serializer.py

@@ -3,6 +3,7 @@ import pickle
 import re
 import sys
 import unittest
+
 from collections import ChainMap
 from collections.abc import Mapping
 
@@ -11,6 +12,7 @@ from django.db import models
 
 from rest_framework import exceptions, fields, relations, serializers
 from rest_framework.fields import Field
+
 from .models import (
     ForeignKeyTarget, NestedForeignKeySource, NullableForeignKeySource
 )
@@ -843,3 +845,63 @@ class TestMultipleObjectsValidation(unittest.TestCase):
                 many=True,
                 partial=True,
             )
+
+
+class MyClass(models.Model):
+    name = models.CharField(max_length=100)
+    value = models.CharField(max_length=100, blank=True)
+
+    app_label = "test"
+
+    @property
+    def is_valid(self):
+        return self.name == 'valid'
+
+
+class MyClassSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = MyClass
+        fields = ('id', 'name', 'value')
+
+    def validate_value(self, value):
+        if value and not self.instance.is_valid:
+            raise serializers.ValidationError(
+                'Status cannot be set for invalid instance')
+        return value
+
+
+class TestMultipleObjectsValidation(unittest.TestCase):
+    def setUp(self):
+        self.objs = [
+            MyClass(name='valid'),
+            MyClass(name='invalid'),
+            MyClass(name='other'),
+        ]
+
+    def test_multiple_objects_are_validated_separately(self):
+
+        serializer = MyClassSerializer(
+            data=[{'value': 'set', 'id': instance.id} for instance in
+                  self.objs],
+            instance=self.objs,
+            many=True,
+            partial=True,
+        )
+
+        assert not serializer.is_valid()
+        assert serializer.errors == [
+            {},
+            {'value': ['Status cannot be set for invalid instance']},
+            {'value': ['Status cannot be set for invalid instance']}
+        ]
+
+    def test_exception_raised_when_data_and_instance_length_different(self):
+
+        with self.assertRaises(AssertionError):
+            serializer = MyClassSerializer(
+                data=[{'value': 'set', 'id': instance.id} for instance in
+                      self.objs],
+                instance=self.objs[:-1],
+                many=True,
+                partial=True,
+            )