From 23b35f1a7b0c46bd573ffc3c02234b25623d3271 Mon Sep 17 00:00:00 2001
From: Berend Klein Haneveld <berendkleinhaneveld@gmail.com>
Date: Tue, 26 May 2026 11:15:27 +0200
Subject: [PATCH] perf: use str.replace in Pointer escape/unescape

Replaces the regex-based escape helpers in patchdiff/pointer.py with
str.replace. For single-character substitutions this is ~3x faster than a
compiled regex, and Pointer.__str__ calls escape() per token on every
serialization.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 patchdiff/pointer.py  | 10 ++--------
 tests/test_pointer.py | 30 +++++++++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/patchdiff/pointer.py b/patchdiff/pointer.py
index cf4dbb1..13b0863 100644
--- a/patchdiff/pointer.py
+++ b/patchdiff/pointer.py
@@ -1,22 +1,16 @@
 from __future__ import annotations
 
-import re
 from typing import Any, Hashable, Iterable
 
 from .types import Diffable
 
-tilde0_re = re.compile("~0")
-tilde1_re = re.compile("~1")
-tilde_re = re.compile("~")
-slash_re = re.compile("/")
-
 
 def unescape(token: str) -> str:
-    return tilde0_re.sub("~", tilde1_re.sub("/", token))
+    return token.replace("~1", "/").replace("~0", "~")
 
 
 def escape(token: str) -> str:
-    return slash_re.sub("~1", tilde_re.sub("~0", token))
+    return token.replace("~", "~0").replace("/", "~1")
 
 
 class Pointer:
diff --git a/tests/test_pointer.py b/tests/test_pointer.py
index 045d7a9..6982557 100644
--- a/tests/test_pointer.py
+++ b/tests/test_pointer.py
@@ -1,4 +1,4 @@
-from patchdiff.pointer import Pointer
+from patchdiff.pointer import Pointer, escape, unescape
 
 
 def test_pointer_get():
@@ -44,3 +44,31 @@ def test_pointer_eq():
 
 def test_pointer_append():
     assert Pointer([1]).append("foo") == Pointer([1, "foo"])
+
+
+def test_escape_unescape_roundtrip():
+    # ~01 is the tricky case: escape must produce ~001, not be confused with
+    # the RFC 6901 escape sequence ~0 followed by '1'.
+    tokens = [
+        "",
+        "plain",
+        "has/slash",
+        "has~tilde",
+        "~/mix",
+        "///",
+        "~~~",
+        "~01",
+    ]
+    expected = {
+        "": "",
+        "plain": "plain",
+        "has/slash": "has~1slash",
+        "has~tilde": "has~0tilde",
+        "~/mix": "~0~1mix",
+        "///": "~1~1~1",
+        "~~~": "~0~0~0",
+        "~01": "~001",
+    }
+    for token in tokens:
+        assert escape(token) == expected[token]
+        assert unescape(escape(token)) == token