fs.cp and fs.cpSync fail to repeatedly copy directory with symlinks

先使用 node:fs 進行重現，並追蹤 node:internal/fs/cp/cp-sync 中的堆疊項目，尤其是 copyDir、onDir 和 getStats。檢查帶有目錄符號連結的重複遞迴複製情況，然後驗證 fs.cpSync、fs.cp 和 fs.promises.cp 在不改變已回報的自身子目錄行為的情況下成功完成第二次複製。

Version

v24.16.0

Platform

Linux machine 7.1.3-cachyos-lto #1-NixOS SMP PREEMPT_DYNAMIC Tue Jan  1 00:00:00 UTC 1980 x86_64 GNU/Linux

Subsystem

fs

What steps will reproduce the bug?

This script reproduces the issue:

root="$(mktemp -d)"
trap 'rm -rf "$root"' EXIT

mkdir "$root/dir" "$root/foo"
ln -s "$root/dir" "$root/foo/link"

ROOT="$root" node <<'NODE'
const fs = require("node:fs");
const root = process.env.ROOT;

fs.cpSync(`${root}/foo`, `${root}/bar`, { recursive: true }); // succeeds
fs.cpSync(`${root}/foo`, `${root}/bar`, { recursive: true }); // throws
NODE

How often does it reproduce? Is there a required condition?

Requires a copying repeatedly a dir containing a symlink to another dir.

What is the expected behavior? Why is that the expected behavior?

The second copy should succeed, replacing bar/link or leaving it unchanged.

What do you see instead?

node:internal/fs/cp/cp-sync:145
    return fsBinding.cpSyncCopyDir(src, dest,
                     ^

Error: Cannot copy /tmp/tmp.61ap1tNPej/dir to a subdirectory of self /tmp/tmp.61ap1tNPej/dir
    at copyDir (node:internal/fs/cp/cp-sync:145:22)
    at onDir (node:internal/fs/cp/cp-sync:137:10)
    at getStats (node:internal/fs/cp/cp-sync:68:12)
    at cpSyncFn (node:internal/fs/cp/cp-sync:58:10)
    at Object.cpSync (node:fs:3158:3)
    at [stdin]:5:4
    at runScriptInThisContext (node:internal/vm:219:10)
    at node:internal/process/execution:451:12
    at [stdin]-wrapper:6:24
    at runScriptInContext (node:internal/process/execution:449:60) {
  code: 'ERR_FS_CP_EINVAL'
}

Node.js v24.16.0

Additional information

Also recreated in:

• Node.js v22.23.1
• Node.js v26.7.0
• Node.js v27.0.0-nightly20260806de333e856d

The result is the same with force: true, force: false, or errorOnExist. fs.cp() and fs.promises.cp() are also affected.

Modifying bar/link, or pointing it to a different directory, makes the second copy succeed.