vfs: fix abort signal, readFile flag, realpath.native, and metadata ops

- Check AbortSignal before VFS fast path in readFile/writeFile/appendFile
- Honor options.flag in readFile/readFileSync on VFS paths
- Route realpath.native/realpathSync.native through VFS handlers
- Implement chmod/chown/utimes/lutimes in MemoryProvider instead of no-ops
- Pass bigint option through VFSStatWatcher to statSync/createZeroStats
- Coerce BigInt positions to Number in MemoryFileHandle read/write
- Track nlink on MemoryEntry, increment on link, decrement on unlink
- Update ctime alongside mtime on content mutations (write/truncate)

Author: mcollina

lib/fs.js

@@ -395,6 +395,7 @@ function readFile(path, options, callback) {
   const h = vfsState.handlers;
   if (h !== null) {
     const opts = typeof options === 'function' ? undefined : options;
+    if (checkAborted(opts?.signal, callback)) return;
     try {
       const result = h.readFileSync(path, opts);
       if (result !== undefined) {
@@ -2611,7 +2612,7 @@ function lchown(path, uid, gid, callback) {
 
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.lchownSync(path);
+    const result = h.lchownSync(path, uid, gid);
     if (result !== undefined) {
       process.nextTick(callback, null);
       return;
@@ -2637,7 +2638,7 @@ function lchownSync(path, uid, gid) {
 
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.lchownSync(path);
+    const result = h.lchownSync(path, uid, gid);
     if (result !== undefined) return;
   }
 
@@ -2717,7 +2718,7 @@ function chown(path, uid, gid, callback) {
 
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.chownSync(path);
+    const result = h.chownSync(path, uid, gid);
     if (result !== undefined) {
       process.nextTick(callback, null);
       return;
@@ -2744,7 +2745,7 @@ function chownSync(path, uid, gid) {
 
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.chownSync(path);
+    const result = h.chownSync(path, uid, gid);
     if (result !== undefined) return;
   }
 
@@ -2882,7 +2883,7 @@ function lutimes(path, atime, mtime, callback) {
 
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.lutimesSync(path);
+    const result = h.lutimesSync(path, atime, mtime);
     if (result !== undefined) {
       process.nextTick(callback, null);
       return;
@@ -2912,7 +2913,7 @@ function lutimesSync(path, atime, mtime) {
 
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.lutimesSync(path);
+    const result = h.lutimesSync(path, atime, mtime);
     if (result !== undefined) return;
   }
 
@@ -2998,6 +2999,7 @@ function writeFile(path, data, options, callback) {
   const h = vfsState.handlers;
   if (h !== null) {
     const opts = typeof options === 'function' ? undefined : options;
+    if (checkAborted(opts?.signal, callback)) return;
     try {
       const result = h.writeFileSync(path, data, opts);
       if (result !== undefined) {
@@ -3137,6 +3139,7 @@ function appendFile(path, data, options, callback) {
   const h = vfsState.handlers;
   if (h !== null) {
     const opts = typeof options === 'function' ? undefined : options;
+    if (checkAborted(opts?.signal, callback)) return;
     try {
       const result = h.appendFileSync(path, data, opts);
       if (result !== undefined) {
@@ -3547,6 +3550,11 @@ function realpathSync(p, options) {
  * @returns {string | Buffer}
  */
 realpathSync.native = (path, options) => {
+  const h = vfsState.handlers;
+  if (h !== null) {
+    const result = h.realpathSync(path, options);
+    if (result !== undefined) return result;
+  }
   options = getOptions(options);
   return binding.realpath(
     getValidatedPath(path),
@@ -3725,6 +3733,19 @@ function realpath(p, options, callback) {
  */
 realpath.native = (path, options, callback) => {
   callback = makeCallback(callback || options);
+  const h = vfsState.handlers;
+  if (h !== null) {
+    try {
+      const result = h.realpathSync(path, options);
+      if (result !== undefined) {
+        process.nextTick(callback, null, result);
+        return;
+      }
+    } catch (err) {
+      process.nextTick(callback, err);
+      return;
+    }
+  }
   options = getOptions(options);
   path = getValidatedPath(path);
   const req = new FSReqCallback();

lib/internal/fs/promises.js

@@ -1186,7 +1186,7 @@ async function lchmod(path, mode) {
 async function lchown(path, uid, gid) {
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.lchownSync(path);
+    const result = h.lchownSync(path, uid, gid);
     if (result !== undefined) return;
   }
 
@@ -1213,7 +1213,7 @@ async function fchown(handle, uid, gid) {
 async function chown(path, uid, gid) {
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.chownSync(path);
+    const result = h.chownSync(path, uid, gid);
     if (result !== undefined) return;
   }
 
@@ -1261,7 +1261,7 @@ async function futimes(handle, atime, mtime) {
 async function lutimes(path, atime, mtime) {
   const h = vfsState.handlers;
   if (h !== null) {
-    const result = h.lutimesSync(path);
+    const result = h.lutimesSync(path, atime, mtime);
     if (result !== undefined) return;
   }
 
@@ -1346,6 +1346,7 @@ async function mkdtempDisposable(prefix, options) {
 async function writeFile(path, data, options) {
   const h = vfsState.handlers;
   if (h !== null) {
+    checkAborted(options?.signal);
     const vfsResult = await h.writeFile(path, data, options);
     if (vfsResult !== undefined) return;
   }
@@ -1388,6 +1389,7 @@ function isCustomIterable(obj) {
 async function appendFile(path, data, options) {
   const h = vfsState.handlers;
   if (h !== null) {
+    checkAborted(options?.signal);
     const vfsResult = await h.appendFile(path, data, options);
     if (vfsResult !== undefined) return;
   }
@@ -1400,6 +1402,7 @@ async function appendFile(path, data, options) {
 async function readFile(path, options) {
   const h = vfsState.handlers;
   if (h !== null) {
+    checkAborted(options?.signal);
     const vfsResult = await h.readFile(path, options);
     if (vfsResult !== undefined) return vfsResult;
   }

lib/internal/vfs/file_handle.js

@@ -4,6 +4,7 @@ const {
   DateNow,
   MathMax,
   MathMin,
+  Number,
   Symbol,
 } = primordials;
 
@@ -363,7 +364,8 @@ class MemoryFileHandle extends VirtualFileHandle {
 
     // Get content (resolves dynamic content providers)
     const content = this.content;
-    const readPos = position !== null && position !== undefined ? position : this.position;
+    const readPos = position !== null && position !== undefined ?
+      Number(position) : this.position;
     const available = content.length - readPos;
 
     if (available <= 0) {
@@ -409,7 +411,8 @@ class MemoryFileHandle extends VirtualFileHandle {
     // In append mode, always write at the end
     const writePos = this.#isAppend() ?
       this.#size :
-      (position !== null && position !== undefined ? position : this.position);
+      (position !== null && position !== undefined ?
+        Number(position) : this.position);
     const data = buffer.subarray(offset, offset + length);
 
     // Expand buffer if needed (geometric doubling for amortized O(1) appends)
@@ -429,10 +432,12 @@ class MemoryFileHandle extends VirtualFileHandle {
       this.#size = neededSize;
     }
 
-    // Update the entry's content and mtime
+    // Update the entry's content, mtime, and ctime
     if (this.#entry) {
+      const now = DateNow();
       this.#entry.content = this.#content.subarray(0, this.#size);
-      this.#entry.mtime = DateNow();
+      this.#entry.mtime = now;
+      this.#entry.ctime = now;
     }
 
     // Update position if not using explicit position
@@ -520,10 +525,12 @@ class MemoryFileHandle extends VirtualFileHandle {
       this.#size = buffer.length;
     }
 
-    // Update the entry's content and mtime
+    // Update the entry's content, mtime, and ctime
     if (this.#entry) {
+      const now = DateNow();
       this.#entry.content = this.#content.subarray(0, this.#size);
-      this.#entry.mtime = DateNow();
+      this.#entry.mtime = now;
+      this.#entry.ctime = now;
     }
 
     this.position = this.#size;
@@ -585,10 +592,12 @@ class MemoryFileHandle extends VirtualFileHandle {
       this.#size = len;
     }
 
-    // Update the entry's content and mtime
+    // Update the entry's content, mtime, and ctime
     if (this.#entry) {
+      const now = DateNow();
       this.#entry.content = this.#content.subarray(0, this.#size);
-      this.#entry.mtime = DateNow();
+      this.#entry.mtime = now;
+      this.#entry.ctime = now;
     }
   }
 

lib/internal/vfs/file_system.js

@@ -640,6 +640,26 @@ class VirtualFileSystem {
     this[kProvider].linkSync(existingProviderPath, newProviderPath);
   }
 
+  chmodSync(filePath, mode) {
+    const providerPath = this.#toProviderPath(filePath);
+    this[kProvider].chmodSync(providerPath, mode);
+  }
+
+  chownSync(filePath, uid, gid) {
+    const providerPath = this.#toProviderPath(filePath);
+    this[kProvider].chownSync(providerPath, uid, gid);
+  }
+
+  utimesSync(filePath, atime, mtime) {
+    const providerPath = this.#toProviderPath(filePath);
+    this[kProvider].utimesSync(providerPath, atime, mtime);
+  }
+
+  lutimesSync(filePath, atime, mtime) {
+    const providerPath = this.#toProviderPath(filePath);
+    this[kProvider].lutimesSync(providerPath, atime, mtime);
+  }
+
   /**
    * Creates a unique temporary directory synchronously.
    * @param {string} prefix The prefix for the temp directory

lib/internal/vfs/provider.js

@@ -244,7 +244,9 @@ class VirtualProvider {
    * @returns {Promise<Buffer|string>}
    */
   async readFile(path, options) {
-    const handle = await this.open(path, 'r');
+    const flag = (typeof options === 'object' && options !== null) ?
+      (options.flag ?? 'r') : 'r';
+    const handle = await this.open(path, flag);
     try {
       return await handle.readFile(options);
     } finally {
@@ -259,7 +261,9 @@ class VirtualProvider {
    * @returns {Buffer|string}
    */
   readFileSync(path, options) {
-    const handle = this.openSync(path, 'r');
+    const flag = (typeof options === 'object' && options !== null) ?
+      (options.flag ?? 'r') : 'r';
+    const handle = this.openSync(path, flag);
     try {
       return handle.readFileSync(options);
     } finally {

lib/internal/vfs/providers/memory.js

@@ -82,6 +82,19 @@ function normalizeFlags(flags) {
   return 'r';
 }
 
+/**
+ * Converts a time argument (Date, number, or string) to milliseconds.
+ * Numbers are treated as seconds (matching Node.js utimes convention).
+ * @param {Date|number|string} time The time value
+ * @returns {number} Milliseconds since epoch
+ */
+function toMs(time) {
+  if (typeof time === 'number') return time * 1000;
+  if (typeof time === 'string') return DateNow(); // Fallback for string timestamps
+  if (typeof time === 'object' && time !== null) return +time;
+  return time;
+}
+
 // Private symbols
 const kRoot = Symbol('kRoot');
 const kReadonly = Symbol('kReadonly');
@@ -108,7 +121,11 @@ class MemoryEntry {
     this.children = null; // For directories
     this.populate = null; // For directories - lazy population callback
     this.populated = true; // For directories - has populate been called?
+    this.nlink = 1;
+    this.uid = 0;
+    this.gid = 0;
     const now = DateNow();
+    this.atime = now;
     this.mtime = now;
     this.ctime = now;
     this.birthtime = now;
@@ -409,6 +426,10 @@ class MemoryProvider extends VirtualProvider {
   #createStats(entry, size, bigint) {
     const options = {
       mode: entry.mode,
+      nlink: entry.nlink,
+      uid: entry.uid,
+      gid: entry.gid,
+      atimeMs: entry.atime,
       mtimeMs: entry.mtime,
       ctimeMs: entry.ctime,
       birthtimeMs: entry.birthtime,
@@ -715,6 +736,7 @@ class MemoryProvider extends VirtualProvider {
     const parent = this.#ensureParent(normalized, false, 'unlink');
     const name = pathPosix.basename(normalized);
     parent.children.delete(name);
+    entry.nlink--;
   }
 
   async unlink(path) {
@@ -786,6 +808,7 @@ class MemoryProvider extends VirtualProvider {
     const name = pathPosix.basename(normalizedNew);
     // Hard link: same entry object referenced by both names
     parent.children.set(name, entry);
+    entry.nlink++;
   }
 
   async link(existingPath, newPath) {
@@ -846,6 +869,36 @@ class MemoryProvider extends VirtualProvider {
     return this.realpathSync(path, options);
   }
 
+  // === METADATA OPERATIONS ===
+
+  chmodSync(path, mode) {
+    const entry = this.#getEntry(path, 'chmod', true);
+    // 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;
+    if (gid >= 0) entry.gid = gid;
+    entry.ctime = DateNow();
+  }
+
+  utimesSync(path, atime, mtime) {
+    const entry = this.#getEntry(path, 'utime', true);
+    entry.atime = toMs(atime);
+    entry.mtime = toMs(mtime);
+    entry.ctime = DateNow();
+  }
+
+  lutimesSync(path, atime, mtime) {
+    const entry = this.#getEntry(path, 'utime', false);
+    entry.atime = toMs(atime);
+    entry.mtime = toMs(mtime);
+    entry.ctime = DateNow();
+  }
+
   // === WATCH OPERATIONS ===
 
   /**