vfs: make lchown update symlink metadata

Route mounted lchown operations through VFS lchown handling and add
memory provider support that does not follow the final symlink.
Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.5
PR-URL: #64573Fixes: #64572
Reviewed-By: Aviv Keller <me@aviv.sh>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: trivikr

doc/api/vfs.md

@@ -156,6 +156,7 @@ signatures as their [`node:fs`][] counterparts:
 *`linkSync(existingPath, newPath)`
 *`chmodSync(path, mode)`
 *`chownSync(path, uid, gid)`
+*`lchownSync(path, uid, gid)`
 *`utimesSync(path, atime, mtime)`
 *`lutimesSync(path, atime, mtime)`
 *`mkdtempSync(prefix)`

lib/internal/vfs/file_system.js

@@ -506,6 +506,11 @@ class VirtualFileSystem {
 this[kProvider].chownSync(providerPath,uid,gid);
 }
 
+lchownSync(filePath,uid,gid){
+constproviderPath=this.#toProviderPath(filePath);
+this[kProvider].lchownSync(providerPath,uid,gid);
+}
+
 utimesSync(filePath,atime,mtime){
 constproviderPath=this.#toProviderPath(filePath);
 this[kProvider].utimesSync(providerPath,atime,mtime);
@@ -1234,7 +1239,7 @@ class VirtualFileSystem {
 
 asynclchown(filePath,uid,gid){
 constproviderPath=toProviderPath(filePath);
-provider.chownSync(providerPath,uid,gid);
+provider.lchownSync(providerPath,uid,gid);
 },
 
 asyncutimes(filePath,atime,mtime){

lib/internal/vfs/provider.js

@@ -235,6 +235,18 @@ class VirtualProvider {
 thrownewERR_METHOD_NOT_IMPLEMENTED('renameSync');
 }
 
+/**
+ * Changes ownership of a path without following the final symbolic link.
+ * Providers with symlink support should override this.
+ * @param {string} path The path
+ * @param {number} uid The user id
+ * @param {number} gid The group id
+ * @returns {void}
+ */
+lchownSync(path,uid,gid){
+returnthis.chownSync(path,uid,gid);
+}
+
 // === DEFAULT IMPLEMENTATIONS (built on primitives) ===
 
 /**

lib/internal/vfs/providers/memory.js

@@ -986,6 +986,13 @@ class MemoryProvider extends VirtualProvider {
 entry.ctime=DateNow();
 }
 
+lchownSync(path,uid,gid){
+constentry=this.#getEntry(path,'chown',false);
+if(uid>=0)entry.uid=uid;
+if(gid>=0)entry.gid=gid;
+entry.ctime=DateNow();
+}
+
 utimesSync(path,atime,mtime){
 constentry=this.#getEntry(path,'utime',true);
 entry.atime=toMs(atime);

lib/internal/vfs/setup.js

@@ -343,7 +343,7 @@ function createVfsHandlers() {
 vfsOpVoid(path,(vfs,n)=>vfs.symlinkSync(target,n,type)),
 chmodSync: (path,mode)=>vfsOpVoid(path,(vfs,n)=>vfs.chmodSync(n,mode)),
 chownSync: (path,uid,gid)=>vfsOpVoid(path,(vfs,n)=>vfs.chownSync(n,uid,gid)),
-lchownSync: (path,uid,gid)=>vfsOpVoid(path,(vfs,n)=>vfs.chownSync(n,uid,gid)),
+lchownSync: (path,uid,gid)=>vfsOpVoid(path,(vfs,n)=>vfs.lchownSync(n,uid,gid)),
 utimesSync: (path,atime,mtime)=>
 vfsOpVoid(path,(vfs,n)=>vfs.utimesSync(n,atime,mtime)),
 lutimesSync: (path,atime,mtime)=>

test/parallel/test-vfs-lchown-symlink.js

@@ -0,0 +1,48 @@
+// Flags: --experimental-vfs
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert');
+constfs=require('fs');
+constfsp=require('fs/promises');
+constpath=require('path');
+constvfs=require('node:vfs');
+
+constmountPoint=path.resolve('/tmp/vfs-lchown-'+process.pid);
+constmyVfs=vfs.create();
+myVfs.writeFileSync('/sync-target.txt','target');
+myVfs.symlinkSync('/sync-target.txt','/sync-link.txt');
+myVfs.writeFileSync('/async-target.txt','target');
+myVfs.symlinkSync('/async-target.txt','/async-link.txt');
+myVfs.writeFileSync('/promise-target.txt','target');
+myVfs.symlinkSync('/promise-target.txt','/promise-link.txt');
+myVfs.mount(mountPoint);
+
+functionassertOwnership(filePath,uid,gid){
+conststats=fs.lstatSync(path.join(mountPoint,filePath));
+assert.strictEqual(stats.uid,uid);
+assert.strictEqual(stats.gid,gid);
+}
+
+(async()=>{
+try{
+fs.lchownSync(path.join(mountPoint,'sync-link.txt'),123,456);
+assertOwnership('/sync-target.txt',0,0);
+assertOwnership('/sync-link.txt',123,456);
+
+awaitnewPromise((resolve,reject)=>{
+fs.lchown(path.join(mountPoint,'async-link.txt'),234,567,(err)=>{
+if(err)reject(err);
+elseresolve();
+});
+});
+assertOwnership('/async-target.txt',0,0);
+assertOwnership('/async-link.txt',234,567);
+
+awaitfsp.lchown(path.join(mountPoint,'promise-link.txt'),345,678);
+assertOwnership('/promise-target.txt',0,0);
+assertOwnership('/promise-link.txt',345,678);
+}finally{
+myVfs.unmount();
+}
+})().then(common.mustCall());