fs: handle recursive watch setup races

Arm directory watchers before reading entries to close the setup
window. Discard stale watcher state when paths disappear so recreated
paths can be watched again.

On AIX, treat ENODEV as missing only when stat confirms the path is
gone. Preserve root throwIfNoEntry behavior and other watch errors.

Fixes: #65698

Signed-off-by: Filip Skokan <panva.ip@gmail.com>
Assisted-by: Codex

Author: panva

lib/internal/fs/recursive_watch.js

@@ -37,6 +37,24 @@ function lazyLoadFsSync() {
 
 let kResistStopPropagation;
 
+const kIsAIX = process.platform === 'aix';
+
+function isPathMissingForWatch(error, file) {
+  if (error.code === 'ENOENT') {
+    return true;
+  }
+  // AIX reports ENODEV when the path disappears before fs.watch() starts.
+  // Check that it is actually gone so other ENODEV errors still propagate.
+  if (!kIsAIX || error.code !== 'ENODEV') {
+    return false;
+  }
+  try {
+    return lazyLoadFsSync().statSync(file, { throwIfNoEntry: false }) === undefined;
+  } catch {
+    return false;
+  }
+}
+
 // Inotify reports changes to a directory's entries, with their names, on the
 // directory's own watch, so one watcher per directory is enough on Linux.
 // kqueue and event ports only report that the directory itself changed, so
@@ -116,56 +134,81 @@ class FSWatcher extends EventEmitter {
   }
 
   #forget(file) {
+    const watcher = this.#watchers.get(file);
+    if (watcher !== undefined) {
+      watcher.close();
+      this.#watchers.delete(file);
+    }
+    this.#entries.delete(file);
+    this.#symbolicLinks.delete(file);
+
     const childPrefix = file + pathSep;
     for (const entry of this.#entries) {
-      if (entry === file || StringPrototypeStartsWith(entry, childPrefix)) {
+      if (StringPrototypeStartsWith(entry, childPrefix)) {
         this.#entries.delete(entry);
         this.#symbolicLinks.delete(entry);
-        const watcher = this.#watchers.get(entry);
-        if (watcher !== undefined) {
-          watcher.close();
+        const childWatcher = this.#watchers.get(entry);
+        if (childWatcher !== undefined) {
+          childWatcher.close();
           this.#watchers.delete(entry);
         }
       }
     }
   }
 
-  // An entry that vanished between being listed and being watched is left to
-  // the directory's own watcher to report.
+  // Report an entry that vanished between being listed and being watched so
+  // the caller can discard its stale bookkeeping.
   #watch(file, onChange) {
-    if (this.#closed || this.#watchers.has(file)) {
-      return;
+    if (this.#closed) {
+      return false;
+    }
+    if (this.#watchers.has(file)) {
+      return true;
     }
     const { watch } = lazyLoadFsSync();
     let watcher;
     try {
       watcher = watch(file, { persistent: this.#options.persistent }, onChange);
     } catch (err) {
-      if (err.code === 'ENOENT') {
-        return;
+      if (isPathMissingForWatch(err, file) &&
+          (file !== this.#rootPath || !this.#options.throwIfNoEntry)) {
+        return false;
       }
       throw err;
     }
     this.#watchers.set(file, watcher);
+    return true;
   }
 
-  // Registers the entries of `folder` that are not known yet (emitting
-  // 'rename' for them unless this is the initial scan) and arms one watcher
-  // for the directory; #addEntry() descends into subdirectories.
+  // Arms one watcher for `folder`, then registers entries that are not known
+  // yet (emitting 'rename' for them unless this is the initial scan);
+  // #addEntry() descends into subdirectories.
   #scanFolder(folder, initial) {
+    if (!this.#watch(folder, (eventType, filename) => this.#onFolderEvent(folder, filename))) {
+      this.#forget(folder);
+      return;
+    }
+
     const { readdirSync } = lazyLoadFsSync();
     let entries;
     try {
       entries = readdirSync(folder, { withFileTypes: true });
     } catch (error) {
-      if (error.code !== 'ENOENT') {
+      if (error.code === 'ENOENT' || error.code === 'ENOTDIR') {
+        if (folder === this.#rootPath && initial &&
+            (error.code !== 'ENOENT' || this.#options.throwIfNoEntry)) {
+          throw error;
+        }
+        if (!initial && !this.#closed) {
+          this.#emit('rename', folder);
+        }
+        this.#forget(folder);
+      } else {
         this.emit('error', error);
       }
       return;
     }
 
-    this.#watch(folder, (eventType, filename) => this.#onFolderEvent(folder, filename));
-
     for (const entry of entries) {
       if (this.#closed) {
         break;
@@ -187,11 +230,15 @@ class FSWatcher extends EventEmitter {
       // The link target is watched so that changes behind the link surface
       // as a 'rename' of the link, as they always have on this code path.
       this.#symbolicLinks.add(file);
-      this.#watch(file, () => this.#emit('rename', file));
+      if (!this.#watch(file, () => this.#emit('rename', file))) {
+        this.#forget(file);
+      }
     } else if (entry.isDirectory()) {
       this.#scanFolder(file, initial);
     } else if (!kDirectoryWatchReportsEntries) {
-      this.#watch(file, () => this.#onEntryEvent(file));
+      if (!this.#watch(file, () => this.#onEntryEvent(file))) {
+        this.#forget(file);
+      }
     }
   }
 
@@ -253,7 +300,7 @@ class FSWatcher extends EventEmitter {
   #watchRootFile(file) {
     const { statSync } = lazyLoadFsSync();
     this.#entries.add(file);
-    this.#watch(file, () => {
+    if (!this.#watch(file, () => {
       if (this.#closed) {
         return;
       }
@@ -263,7 +310,9 @@ class FSWatcher extends EventEmitter {
       } else {
         this.emit('change', 'change', pathBasename(file));
       }
-    });
+    })) {
+      this.#forget(file);
+    }
   }
 
   [kFSWatchStart](filename) {

test/parallel/parallel.status

@@ -105,8 +105,6 @@ test-fs-watch-ignore-regexp: SKIP
 test-runner-coverage: PASS, FLAKY
 # https://github.com/nodejs/node/issues/54346
 test-esm-loader-hooks-inspect-wait: PASS, FLAKY
-# https://github.com/nodejs/node/issues/65697
-fs-watch-recursive-delete-race: SKIP
 
 [$system==ibmi]
 # https://github.com/nodejs/node/pull/30819