Add code to replace restframework_bulk package for bulk create and simplify UserListSerializer

`to_internal_value()` function is not longer overriden in UserListSerializer, this is due to explicitly stating the `id` field in UserSerializer as mentioned in the documentation.
Override `create()` method in UserListSerializer and override `get_serializer()` method in `UserViewSet` to support bulk creation.

2 files changed, 35 insertions, 58 deletions

diff --git a/pydis_site/apps/api/serializers.py b/pydis_site/apps/api/serializers.py
index 0589ce77..21c488a8 100644
--- a/pydis_site/apps/api/serializers.py
+++ b/pydis_site/apps/api/serializers.py
@@ -1,15 +1,13 @@
 """Converters from Django models to data interchange formats and back."""
 from django.db.models.query import QuerySet
 from rest_framework.serializers import (
+    IntegerField,
     ListSerializer,
     ModelSerializer,
     PrimaryKeyRelatedField,
     ValidationError
 )
-from rest_framework.settings import api_settings
-from rest_framework.utils import html
 from rest_framework.validators import UniqueTogetherValidator
-from rest_framework_bulk import BulkSerializerMixin
 
 from .models import (
     BotSetting,
@@ -271,55 +269,18 @@ class TagSerializer(ModelSerializer):
 class UserListSerializer(ListSerializer):
     """List serializer for User model to handle bulk updates."""
 
-    def to_internal_value(self, data: list) -> list:
-        """
-        Overriding `to_internal_value` function with a few changes to support bulk updates.
-
-        ref: https://github.com/miki725/django-rest-framework-bulk/issues/68
+    def create(self, validated_data: list) -> list:
+        """Override create method to optimize django queries."""
+        present_users = User.objects.all()
+        new_users = []
+        present_user_ids = [user.id for user in present_users]
 
-        List of dicts of native values <- List of dicts of primitive datatypes.
-        """
-        if html.is_html_input(data):
-            data = html.parse_html_list(data, default=[])
+        for user_dict in validated_data:
+            if user_dict["id"] in present_user_ids:
+                raise ValidationError({"id": "User already exists."})
+            new_users.append(User(**user_dict))
 
-        if not isinstance(data, list):
-            message = self.error_messages['not_a_list'].format(
-                input_type=type(data).__name__
-            )
-            raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [message]
-            }, code='not_a_list')
-
-        if not self.allow_empty and len(data) == 0:
-            message = self.error_messages['empty']
-            raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [message]
-            }, code='empty')
-
-        ret = []
-        errors = []
-
-        for item in data:
-            # inserted code
-            # -----------------
-            try:
-                self.child.instance = self.instance.get(id=item['id'])
-            except (User.DoesNotExist, AttributeError):
-                self.child.instance = None
-            # -----------------
-            self.child.initial_data = item
-            try:
-                validated = self.child.run_validation(item)
-            except ValidationError as exc:
-                errors.append(exc.detail)
-            else:
-                ret.append(validated)
-                errors.append({})
-
-        if any(errors):
-            raise ValidationError(errors)
-
-        return ret
+        return User.objects.bulk_create(new_users)
 
     def update(self, instance: QuerySet, validated_data: list) -> list:
         """
@@ -331,17 +292,19 @@ class UserListSerializer(ListSerializer):
         data_mapping = {item['id']: item for item in validated_data}
 
         updated = []
-        for book_id, data in data_mapping.items():
-            book = instance_mapping.get(book_id, None)
-            if book is not None:
-                updated.append(self.child.update(book, data))
+        for user_id, data in data_mapping.items():
+            user = instance_mapping.get(user_id, None)
+            if user:
+                updated.append(self.child.update(user, data))
 
         return updated
 
 
-class UserSerializer(BulkSerializerMixin, ModelSerializer):
+class UserSerializer(ModelSerializer):
     """A class providing (de-)serialization of `User` instances."""
 
+    id = IntegerField(min_value=0)
+
     class Meta:
         """Metadata defined for the Django REST Framework."""
 
diff --git a/pydis_site/apps/api/viewsets/bot/user.py b/pydis_site/apps/api/viewsets/bot/user.py
index d64ca113..d015fe71 100644
--- a/pydis_site/apps/api/viewsets/bot/user.py
+++ b/pydis_site/apps/api/viewsets/bot/user.py
@@ -3,8 +3,8 @@ from rest_framework.decorators import action
 from rest_framework.pagination import PageNumberPagination
 from rest_framework.request import Request
 from rest_framework.response import Response
+from rest_framework.serializers import ModelSerializer
 from rest_framework.viewsets import ModelViewSet
-from rest_framework_bulk import BulkCreateModelMixin
 
 from pydis_site.apps.api.models.bot.user import User
 from pydis_site.apps.api.serializers import UserSerializer
@@ -17,7 +17,7 @@ class UserListPagination(PageNumberPagination):
     page_size_query_param = "page_size"
 
 
-class UserViewSet(BulkCreateModelMixin, ModelViewSet):
+class UserViewSet(ModelViewSet):
     """
     View providing CRUD operations on Discord users through the bot.
 
@@ -142,7 +142,14 @@ class UserViewSet(BulkCreateModelMixin, ModelViewSet):
     queryset = User.objects.all()
     pagination_class = UserListPagination
 
-    @action(detail=False, methods=["PATCH"])
+    def get_serializer(self, *args, **kwargs) -> ModelSerializer:
+        """Set Serializer many attribute to True if request body contains a list."""
+        if isinstance(kwargs.get('data', {}), list):
+            kwargs['many'] = True
+
+        return super().get_serializer(*args, **kwargs)
+
+    @action(detail=False, methods=["PATCH"], name='user-bulk-patch')
     def bulk_patch(self, request: Request) -> Response:
         """
         Update multiple User objects in a single request.
@@ -186,6 +193,13 @@ class UserViewSet(BulkCreateModelMixin, ModelViewSet):
 
         filtered_instances = queryset.filter(id__in=object_ids)
 
+        if filtered_instances.count() != len(object_ids):
+            # If all user objects passed in request.body are not present in the database.
+            resp = {
+                "Error": "User object not found."
+            }
+            return Response(resp, status=status.HTTP_404_NOT_FOUND)
+
         serializer = self.get_serializer(
             instance=filtered_instances,
             data=request.data,