From f75daed0a07dd013650dca7b5db6dfb34890f5d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebasti=C3=A1n=20Ram=C3=ADrez?= <tiangolo@gmail.com>
Date: Fri, 12 Dec 2025 15:08:49 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20extracting=20attributes=20?=
 =?UTF-8?q?for=20old=20Pydantic=20versions?=
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---
 fastapi/_compat/v2.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fastapi/_compat/v2.py b/fastapi/_compat/v2.py
index d7150498f..eb5c06edd 100644
--- a/fastapi/_compat/v2.py
+++ b/fastapi/_compat/v2.py
@@ -78,10 +78,15 @@ _Attrs = {
 
 # TODO: remove when dropping support for Pydantic < v2.12.3
 def asdict(field_info: FieldInfo) -> Dict[str, Any]:
+    attributes = {}
+    for attr in _Attrs:
+        value = getattr(field_info, attr, Undefined)
+        if value is not Undefined:
+            attributes[attr] = value
     return {
         "annotation": field_info.annotation,
         "metadata": field_info.metadata,
-        "attributes": {attr: getattr(field_info, attr) for attr in _Attrs},
+        "attributes": attributes,
     }