fs: do not crash if the watched file is removed while setting up watch

Signed-off-by: Matteo Collina <hello@matteocollina.com>
PR-URL: nodejs#53452
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>

lib/internal/fs/recursive_watch.js

@@ -83,7 +83,7 @@ class FSWatcher extends EventEmitter {
     this.#closed = true;
 
     for (const file of this.#files.keys()) {
-      this.#watchers.get(file).close();
+      this.#watchers.get(file)?.close();
       this.#watchers.delete(file);
     }
 
@@ -98,7 +98,7 @@ class FSWatcher extends EventEmitter {
     for (const filename of this.#files.keys()) {
       if (StringPrototypeStartsWith(filename, file)) {
         this.#files.delete(filename);
-        this.#watchers.get(filename).close();
+        this.#watchers.get(filename)?.close();
         this.#watchers.delete(filename);
       }
     }
@@ -126,9 +126,16 @@ class FSWatcher extends EventEmitter {
             this.#symbolicFiles.add(f);
           }
 
-          this.#watchFile(f);
-          if (file.isDirectory() && !file.isSymbolicLink()) {
-            this.#watchFolder(f);
+          try {
+            this.#watchFile(f);
+            if (file.isDirectory() && !file.isSymbolicLink()) {
+              this.#watchFolder(f);
+            }
+          } catch (err) {
+            // Ignore ENOENT
+            if (err.code !== 'ENOENT') {
+              throw err;
+            }
           }
         }
       }

test/parallel/test-fs-watch-recursive-linux-parallel-remove.js

@@ -0,0 +1,33 @@
+'use strict';
+
+const common = require('../common');
+
+if (!common.isLinux)
+  common.skip('This test can run only on Linux');
+
+// Test that the watcher do not crash if the file "disappears" while
+// watch is being set up.
+
+const path = require('node:path');
+const fs = require('node:fs');
+const { spawn } = require('node:child_process');
+
+const tmpdir = require('../common/tmpdir');
+const testDir = tmpdir.path;
+tmpdir.refresh();
+
+const watcher = fs.watch(testDir, { recursive: true });
+watcher.on('change', function(event, filename) {
+  // This console.log makes the error happen
+  // do not remove
+  console.log(filename, event);
+});
+
+const testFile = path.join(testDir, 'a');
+const child = spawn(process.argv[0], ['-e', `const fs = require('node:fs'); for (let i = 0; i < 10000; i++) { const fd = fs.openSync('${testFile}', 'w'); fs.writeSync(fd, Buffer.from('hello')); fs.rmSync('${testFile}') }`], {
+  stdio: 'inherit'
+});
+
+child.on('exit', function() {
+  watcher.close();
+});