Normalize RECORD paths when writing

src/installer/records.py

@@ -6,7 +6,7 @@
 import os
 from collections.abc import Iterable, Iterator
 from dataclasses import dataclass
-from pathlib import Path
+from pathlib import Path, PureWindowsPath
 from typing import BinaryIO, cast
 
 from installer.utils import copyfileobj_with_hashing, get_stream_length
@@ -106,8 +106,7 @@ def to_row(self, path_prefix: str | None = None) -> tuple[str, str, str]:
             path = self.path
 
         # Convert Windows paths to use / for consistency
-        if os.sep == "\\":
-            path = path.replace("\\", "/")  # pragma: no cover
+        path = PureWindowsPath(path).as_posix()
 
         return (
             path,

tests/test_records.py

@@ -3,6 +3,7 @@
 
 import pytest
 
+import installer.records
 from installer.records import Hash, InvalidRecordEntry, RecordEntry, parse_record_file
 
 
@@ -176,6 +177,34 @@ def test_string_representation_with_prefix(
         )
         assert record.to_row("prefix/") == expected_row
 
+    def test_string_representation_with_backslash_path(self, monkeypatch):
+        monkeypatch.setattr(installer.records.os, "sep", "/")
+        record = RecordEntry.from_elements(
+            r"distribution-1.0.dist-info\RECORD",
+            "",
+            "",
+        )
+
+        assert record.to_row() == (
+            "distribution-1.0.dist-info/RECORD",
+            "",
+            "",
+        )
+
+    def test_string_representation_with_backslash_path_and_prefix(self, monkeypatch):
+        monkeypatch.setattr(installer.records.os, "sep", "/")
+        record = RecordEntry.from_elements(
+            r"bin\script.py",
+            "",
+            "",
+        )
+
+        assert record.to_row("prefix/") == (
+            "prefix/bin/script.py",
+            "",
+            "",
+        )
+
     def test_equality(self):
         record = RecordEntry.from_elements(
             "file.py",