From e22399d1bf31bcd908a0bbb07dc1384c22a172c1 Mon Sep 17 00:00:00 2001
From: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Date: Thu, 27 Nov 2025 10:59:39 +0100
Subject: [PATCH] Fixed #23533 -- Allow defining initial filters on QuerySet
 classes.

Thanks Simon Charette for the implementation idea.
---
 django/db/models/manager.py |  6 ++++--
 django/db/models/query.py   | 24 ++++++++++++++++++++++--
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/django/db/models/manager.py b/django/db/models/manager.py
index 467e79f9b9..b8648d76cd 100644
--- a/django/db/models/manager.py
+++ b/django/db/models/manager.py
@@ -1,6 +1,7 @@
 import copy
 import inspect
-from functools import wraps
+import types
+from functools import partial, wraps
 from importlib import import_module
 
 from django.db import router
@@ -90,7 +91,8 @@ class BaseManager:
 
         new_methods = {}
         for name, method in inspect.getmembers(
-            queryset_class, predicate=inspect.isfunction
+            queryset_class,
+            predicate=lambda member: isinstance(member, (types.FunctionType, partial)),
         ):
             # Only copy missing methods.
             if hasattr(cls, name):
diff --git a/django/db/models/query.py b/django/db/models/query.py
index 73d6717bce..089aa5d914 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -29,7 +29,7 @@ from django.db.models.deletion import Collector
 from django.db.models.expressions import Case, DatabaseDefault, F, Value, When
 from django.db.models.fetch_modes import FETCH_ONE
 from django.db.models.functions import Cast, Trunc
-from django.db.models.query_utils import FilteredRelation, Q
+from django.db.models.query_utils import FilteredRelation, Q, class_or_instance_method
 from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, ROW_COUNT
 from django.db.models.utils import (
     AltersData,
@@ -300,6 +300,8 @@ class FlatValuesListIterable(BaseIterable):
 class QuerySet(AltersData):
     """Represent a lazy database lookup for a set of objects."""
 
+    _initial_filter = None
+
     def __init__(self, model=None, query=None, using=None, hints=None):
         self.model = model
         self._db = using
@@ -323,6 +325,8 @@ class QuerySet(AltersData):
             negate, args, kwargs = self._deferred_filter
             self._filter_or_exclude_inplace(negate, args, kwargs)
             self._deferred_filter = None
+        if self._initial_filter is not None:
+            self._query.add_q(self._initial_filter)
         return self._query
 
     @query.setter
@@ -1618,7 +1622,20 @@ class QuerySet(AltersData):
         """
         return self._chain()
 
-    def filter(self, *args, **kwargs):
+    def _class_filter(cls, *args, **kwargs):
+        if invalid_kwargs := PROHIBITED_FILTER_KWARGS.intersection(kwargs):
+            invalid_kwargs_str = ", ".join(f"'{k}'" for k in sorted(invalid_kwargs))
+            raise TypeError(f"The following kwargs are invalid: {invalid_kwargs_str}")
+        initial_filter = Q(*args, **kwargs)
+        initial_filter_id = id(initial_filter)
+        class_name = f"{cls.__name__}WithFilter{initial_filter_id}"
+        return type(
+            class_name,
+            (cls,),
+            {"_initial_filter": initial_filter},
+        )
+
+    def _instance_filter(self, *args, **kwargs):
         """
         Return a new QuerySet instance with the args ANDed to the existing
         set.
@@ -1626,6 +1643,9 @@ class QuerySet(AltersData):
         self._not_support_combined_queries("filter")
         return self._filter_or_exclude(False, args, kwargs)
 
+    filter = class_or_instance_method(_class_filter, _instance_filter)
+    _class_filter = classmethod(_class_filter)
+
     def exclude(self, *args, **kwargs):
         """
         Return a new QuerySet instance with NOT (args) ANDed to the existing
-- 
2.43.0