vfs: make lchmod update symlink mode

Use a non-following provider operation for lchmod so it updates the
symbolic link metadata instead of changing the target file mode.

Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.5
PR-URL: #64350
Fixes: #64349
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: trivikr

lib/internal/vfs/file_system.js

@@ -1255,7 +1255,7 @@ class VirtualFileSystem {
 
       async lchmod(filePath, mode) {
         const providerPath = toProviderPath(filePath);
-        provider.chmodSync(providerPath, mode);
+        provider.lchmodSync(providerPath, mode);
       },
 
       watch(filePath, options) {

lib/internal/vfs/providers/memory.js

@@ -957,6 +957,13 @@ class MemoryProvider extends VirtualProvider {
     entry.ctime = DateNow();
   }
 
+  lchmodSync(path, mode) {
+    const entry = this.#getEntry(path, 'chmod', false);
+    // Preserve file type bits, update permission bits
+    entry.mode = (entry.mode & ~0o7777) | (mode & 0o7777);
+    entry.ctime = DateNow();
+  }
+
   chownSync(path, uid, gid) {
     const entry = this.#getEntry(path, 'chown', true);
     if (uid >= 0) entry.uid = uid;

lib/internal/vfs/providers/real.js

@@ -13,6 +13,9 @@ const { VirtualProvider } = require('internal/vfs/provider');
 const { VirtualFileHandle } = require('internal/vfs/file_handle');
 const { getValidatedPath } = require('internal/fs/utils');
 const { setOwnProperty } = require('internal/util');
+const {
+  ERR_METHOD_NOT_IMPLEMENTED,
+} = require('internal/errors').codes;
 const {
   createEACCES,
   createEBADF,
@@ -517,6 +520,14 @@ class RealFSProvider extends VirtualProvider {
     return fs.promises.access(realPath, mode);
   }
 
+  lchmodSync(vfsPath, mode) {
+    if (fs.lchmodSync === undefined) {
+      throw new ERR_METHOD_NOT_IMPLEMENTED('lchmodSync');
+    }
+    const realPath = this.#resolvePath(vfsPath, false);
+    fs.lchmodSync(realPath, mode);
+  }
+
   copyFileSync(srcVfsPath, destVfsPath, mode) {
     const srcRealPath = this.#resolvePath(srcVfsPath);
     const destRealPath = this.#resolvePath(destVfsPath);

test/parallel/test-vfs-fs-promises.js

@@ -75,6 +75,16 @@ const vfs = require('node:vfs');
   await fsp.utimes(p('src/hello.txt'), now, now);
   await fsp.lutimes(p('src/hello.txt'), now, now);
 
+  await fsp.lchmod(p('src/plnk.txt'), 0o700);
+  assert.strictEqual(
+    (await fsp.lstat(p('src/hello.txt'))).mode & 0o777,
+    0o644,
+  );
+  assert.strictEqual(
+    (await fsp.lstat(p('src/plnk.txt'))).mode & 0o777,
+    0o700,
+  );
+
   // FileHandle via fsp.open
   const handle = await fsp.open(p('src/hello.txt'), 'r');
   assert.strictEqual(await handle.readFile('utf8'), 'hello');