From 7c491dfcb1448b102598f0e3e8e0468de6077cc6 Mon Sep 17 00:00:00 2001
From: Amandeep vishwkarma <amandeepvishwkarma07@gmail.com>
Date: Mon, 18 May 2026 20:43:07 +0530
Subject: [PATCH] Fix map/groupby filters ignoring default=None for missing
 attributes

---
 src/jinja2/filters.py | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/jinja2/filters.py b/src/jinja2/filters.py
index c46e20c10..a1864b71c 100644
--- a/src/jinja2/filters.py
+++ b/src/jinja2/filters.py
@@ -55,11 +55,15 @@ def ignore_case(value: V) -> V:
     return value
 
 
+_MISSING = object()
+"""Sentinel to distinguish 'no default given' from ``default=None``."""
+
+
 def make_attrgetter(
     environment: "Environment",
     attribute: str | int | None,
     postprocess: t.Callable[[t.Any], t.Any] | None = None,
-    default: t.Any | None = None,
+    default: t.Any = _MISSING,
 ) -> t.Callable[[t.Any], t.Any]:
     """Returns a callable that looks up the given attribute from a
     passed object with the rules of the environment.  Dots are allowed
@@ -72,7 +76,7 @@ def attrgetter(item: t.Any) -> t.Any:
         for part in parts:
             item = environment.getitem(item, part)
 
-            if default is not None and isinstance(item, Undefined):
+            if default is not _MISSING and isinstance(item, Undefined):
                 item = default
 
         if postprocess is not None:
@@ -1199,7 +1203,7 @@ def sync_do_groupby(
     environment: "Environment",
     value: "t.Iterable[V]",
     attribute: str | int,
-    default: t.Any | None = None,
+    default: t.Any = _MISSING,
     case_sensitive: bool = False,
 ) -> "list[_GroupTuple]":
     """Group a sequence of objects by an attribute using Python's
@@ -1283,7 +1287,7 @@ async def do_groupby(
     environment: "Environment",
     value: "t.AsyncIterable[V] | t.Iterable[V]",
     attribute: str | int,
-    default: t.Any | None = None,
+    default: t.Any = _MISSING,
     case_sensitive: bool = False,
 ) -> "list[_GroupTuple]":
     expr = make_attrgetter(
@@ -1720,7 +1724,7 @@ def prepare_map(
 ) -> t.Callable[[t.Any], t.Any]:
     if not args and "attribute" in kwargs:
         attribute = kwargs.pop("attribute")
-        default = kwargs.pop("default", None)
+        default = kwargs.pop("default", _MISSING)
 
         if kwargs:
             raise FilterArgumentError(