From 818b2eeaa922143eab7588389b2b44e326819bb0 Mon Sep 17 00:00:00 2001
From: Andrew El-Kadi <aelkadi@google.com>
Date: Tue, 28 Oct 2025 11:47:10 -0700
Subject: [PATCH] Allow negative indices in `daglish_extensions.parse_path`.

PiperOrigin-RevId: 825139895
---
 fiddle/_src/daglish_extensions.py      | 2 +-
 fiddle/_src/daglish_extensions_test.py | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fiddle/_src/daglish_extensions.py b/fiddle/_src/daglish_extensions.py
index b65b474d..4f37ab4e 100644
--- a/fiddle/_src/daglish_extensions.py
+++ b/fiddle/_src/daglish_extensions.py
@@ -122,7 +122,7 @@ def is_unshareable(value: Any) -> bool:
         "|".join([
             r"\.(?P<attr_name>[\w_]+)",
             # future improvement: support escape sequences.
-            r"\[(?P<key>\d+|'[^']+'|\"[^\"]+\")\]",
+            r"\[(?P<key>-?\d+|'[^']+'|\"[^\"]+\")\]",
         ])
     )
 )
diff --git a/fiddle/_src/daglish_extensions_test.py b/fiddle/_src/daglish_extensions_test.py
index 5925f2d9..8ac5a1c1 100644
--- a/fiddle/_src/daglish_extensions_test.py
+++ b/fiddle/_src/daglish_extensions_test.py
@@ -94,6 +94,14 @@ def fn(x: int) -> int:
               daglish.Key("bar"),
           ),
       },
+      {
+          "path": "[-1][0].foo",
+          "expected": (
+              daglish.Key(-1),
+              daglish.Key(0),
+              daglish.Attr("foo"),
+          ),
+      },
   )
   def test_parse_path(self, path, expected):
     actual = daglish_extensions.parse_path(path)