test: add test for mkdir recursive on read-only fs

mkdirSync with { recursive: true } on a read-only filesystem
incorrectly throws ENOENT instead of the expected EROFS error.
This test demonstrates the bug by mounting a read-only tmpfs
via sudo and verifying the error code.

The test requires passwordless sudo to mount a read-only tmpfs.
In environments without this capability (such as ci.nodejs.org),
the test is skipped with a warning message explaining why.

Refs: nodejs#47098
Refs: nodejs#48105
Signed-off-by: Kenny Yeo <[email protected]>

Author: kennyhyun

test/parallel/test-fs-mkdir.js

@@ -22,6 +22,7 @@
 'use strict';
 const common = require('../common');
 const assert = require('assert');
+const child_process = require('child_process');
 const fs = require('fs');
 const path = require('path');
 const { isMainThread } = require('worker_threads');
@@ -184,6 +185,37 @@ function nextdir() {
   }));
 }
 
+// `mkdirp` when folder was readonly.
+if (common.isLinux) {
+  const roTmpfsPath = path.join(tmpdir.path, 'ro-tmpfs');
+  fs.mkdirSync(roTmpfsPath);
+
+  const { status, stderr } = child_process.spawnSync(
+    'sudo', ['-n', 'mount', '-t', 'tmpfs', '-o', 'ro', 'tmpfs', roTmpfsPath],
+    { stdio: 'pipe', encoding: 'utf8' }
+  );
+
+  if (status !== 0) {
+    console.warn(
+      'Cannot test EROFS: passwordless sudo required to mount read-only tmpfs. ' +
+      `Mount failed with status ${status}: ${stderr.trim()}`
+    );
+  } else {
+    const pathname = path.join(roTmpfsPath, nextdir());
+    assert.throws(
+      () => { fs.mkdirSync(pathname, { recursive: true }); },
+      {
+        code: 'EROFS',
+        message: /EROFS:.*mkdir/,
+        name: 'Error',
+        syscall: 'mkdir',
+      }
+    );
+    child_process.spawnSync('sudo', ['-n', 'umount', roTmpfsPath]);
+  }
+  fs.rmdirSync(roTmpfsPath);
+}
+
 // `mkdirp` when path is a file.
 {
   const pathname = tmpdir.resolve(nextdir(), nextdir());