[v18.x backport] fs: fix nonNativeWatcher leak of StatWatchers

lib/internal/fs/recursive_watch.js

@@ -154,14 +154,11 @@ class FSWatcher extends EventEmitter {
             this.#symbolicFiles.add(f);
           }
 
+          this.#files.set(f, file);
           if (file.isFile()) {
             this.#watchFile(f);
-          } else {
-            this.#files.set(f, file);
-
-            if (file.isDirectory() && !file.isSymbolicLink()) {
-              await this.#watchFolder(f);
-            }
+          } else if (file.isDirectory() && !file.isSymbolicLink()) {
+            await this.#watchFolder(f);
           }
         }
       }
@@ -202,6 +199,9 @@ class FSWatcher extends EventEmitter {
         this.emit('change', 'rename', pathRelative(this.#rootPath, file));
       } else if (currentStats.isDirectory()) {
         this.#watchFolder(file);
+      } else {
+        // Watching a directory will trigger a change event for child files)
+        this.emit('change', 'change', pathRelative(this.#rootPath, file));
       }
     });
   }

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

@@ -1,6 +1,7 @@
 'use strict';
 
 const common = require('../common');
+const { setTimeout } = require('timers/promises');
 
 
 const assert = require('assert');
@@ -52,3 +53,59 @@ if (common.isOSX) {
 process.on('exit', function() {
   assert(watcherClosed, 'watcher Object was not closed');
 });
+
+(async () => {
+  // Watch a folder and update an already existing file in it.
+
+  const rootDirectory = fs.mkdtempSync(testDir + path.sep);
+  const testDirectory = path.join(rootDirectory, 'test-0');
+  fs.mkdirSync(testDirectory);
+
+  const testFile = path.join(testDirectory, 'file-1.txt');
+  fs.writeFileSync(testFile, 'hello');
+
+  const watcher = fs.watch(testDirectory, { recursive: true });
+  let watcherClosed = false;
+  watcher.on('change', common.mustCallAtLeast(function(event, filename) {
+    // Libuv inconsistenly emits a rename event for the file we are watching
+    assert.ok(event === 'change' || event === 'rename');
+
+    if (filename === path.basename(testFile)) {
+      watcher.close();
+      watcherClosed = true;
+    }
+  }));
+
+  await setTimeout(common.platformTimeout(100));
+  fs.writeFileSync(testFile, 'hello');
+
+  process.once('exit', function() {
+    assert(watcherClosed, 'watcher Object was not closed');
+  });
+})().then(common.mustCall());
+
+(async () => {
+  // Assert recursive watch does not leak handles
+  const rootDirectory = fs.mkdtempSync(testDir + path.sep);
+  const testDirectory = path.join(rootDirectory, 'test-7');
+  const filePath = path.join(testDirectory, 'only-file.txt');
+  fs.mkdirSync(testDirectory);
+
+  let watcherClosed = false;
+  const watcher = fs.watch(testDirectory, { recursive: true });
+  watcher.on('change', common.mustCallAtLeast(async (event, filename) => {
+    await setTimeout(common.platformTimeout(100));
+    if (filename === path.basename(filePath)) {
+      watcher.close();
+      watcherClosed = true;
+    }
+    await setTimeout(common.platformTimeout(100));
+    assert(!process._getActiveHandles().some((handle) => handle.constructor.name === 'StatWatcher'));
+  }));
+
+  process.on('exit', function() {
+    assert(watcherClosed, 'watcher Object was not closed');
+  });
+  await setTimeout(common.platformTimeout(100));
+  fs.writeFileSync(filePath, 'content');
+})().then(common.mustCall());