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Windows: path.parse rebuilds root/dir with backslashes where Node preserves input separators #10407
Description
Found triaging #10385's Windows gap-suite failures (test_gap_node_path).
The divergence
$ node --experimental-strip-types test-files/test_gap_node_path.ts # Node 26.5.1, Windows
/
/home/user
$ ./test_gap_node_path.exe # Perry
\
\home\user
12 of the fixture's 14 lines match; only path.parse('/home/user/file.txt')'s
root and dir differ.
Cause
js_path_win32_parse (crates/perry-runtime/src/path.rs:1578) reconstructs
root and dir from parsed structure with hardcoded separators —
r.push('\\'), d.push('\\'), head_segments.join("\\").
Node's win32.parse never rebuilds: every field is a slice of the input, so
whatever separator the caller wrote is what comes back. Perry is arguably more
"correctly win32" here, which is still a divergence.
The contract, measured on the pinned oracle
require('path').win32.parse(x) on Node 26.5.1 / Windows:
| input | root | dir | base |
|---|---|---|---|
/home/user/file.txt |
/ |
/home/user |
file.txt |
C:/a/b/c.txt |
C:/ |
C:/a/b |
c.txt |
C:\a\b\c.txt |
C:\ |
C:\a\b |
c.txt |
//server/share/f.txt |
//server/share/ |
//server/share/ |
f.txt |
/a |
/ |
/ |
a |
\a\b |
\ |
\a |
b |
C:foo/bar.txt |
C: |
C:foo |
bar.txt |
/a/b/ |
/ |
/a |
b |
C:/a/ |
C:/ |
C:/ |
a |
/ |
/ |
/ |
(empty) |
// |
/ |
/ |
(empty) |
C: |
C: |
C: |
(empty) |
a/b |
(empty) | a |
b |
a |
(empty) | (empty) | a |
| (empty) | (empty) | (empty) | (empty) |
/a/b//c |
/ |
/a/b/ |
c |
C://a//b |
C:/ |
C://a/ |
b |
The rows that make this more than a separator swap: // roots to / (not UNC —
there is no share), repeated separators survive inside dir
(/a/b//c -> /a/b/), and a trailing separator is dropped for base while the
one before it is kept in dir.
Suggested fix
Derive root/dir/base as offsets into the input and slice, the way Node
does, instead of rebuilding from split_win32's components. The table above is
directly usable as a test vector.
Deliberately not attempted in #10385 / PR #10403: the rewrite touches every
Windows path consumer, and trading a known two-line divergence for unverified
behaviour across all of them needed more verification than that pass could give
it.
Context: one of 22 Windows-specific gap failures identified in #10403. The rest
cluster as fs/errno (5), locale/TZ (4), process/os (4), module resolution (2),
misc (5).
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