perf: use str.replace in Pointer escape/unescape

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:

tests/test_pointer.py

@@ -1,6 +1,6 @@
 import pytest
 
-from patchdiff.pointer import Pointer
+from patchdiff.pointer import Pointer, escape, unescape
 
 
 def test_pointer_get():
@@ -48,6 +48,34 @@ 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
+
+
 def test_pointer_evaluate_raises_on_missing_dict_key():
     with pytest.raises(KeyError):
         Pointer(["missing", "key"]).evaluate({"present": 1})