watch: cancel pending restart on shutdown

lib/internal/main/watch_mode.js

@@ -83,10 +83,13 @@ ArrayPrototypeForEach(kWatchedPaths, (p) => watcher.watchPath(p));
 
 let graceTimer;
 let child;
+let childExitPromise;
 let exited;
+let stopping;
 
 function start() {
   exited = false;
+  stopping = false;
   const stdio = kShouldFilterModules ? ['inherit', 'inherit', 'inherit', 'ipc'] : 'inherit';
   child = spawn(process.execPath, argsWithoutWatchOptions, {
     stdio,
@@ -103,29 +106,36 @@ function start() {
     ArrayPrototypeForEach(kOptionalEnvFiles,
                           (file) => watcher.filterFile(resolve(file), undefined, { allowMissing: true }));
   }
-  child.once('exit', (code) => {
+  childExitPromise = once(child, 'exit').then(({ 0: code }) => {
     exited = true;
+    if (stopping) {
+      return code;
+    }
     const waitingForChanges = 'Waiting for file changes before restarting...';
     if (code === 0) {
       process.stdout.write(`${blue}Completed running ${kCommandStr}. ${waitingForChanges}${white}\n`);
     } else {
       process.stdout.write(`${red}Failed running ${kCommandStr}. ${waitingForChanges}${white}\n`);
     }
+    return code;
   });
   return child;
 }
 
 async function killAndWait(signal = kKillSignal, force = false) {
-  child?.removeAllListeners();
-  if (!child) {
+  const processToKill = child;
+  const onExit = childExitPromise;
+  if (!processToKill) {
     return;
   }
-  if ((child.killed || exited) && !force) {
+  if ((processToKill.killed || exited) && !force) {
     return;
   }
-  const onExit = once(child, 'exit');
-  child.kill(signal);
-  const { 0: exitCode } = await onExit;
+  stopping = true;
+  if (!exited && processToKill.exitCode === null && processToKill.signalCode === null) {
+    processToKill.kill(signal);
+  }
+  const exitCode = await onExit;
   return exitCode;
 }
 

lib/internal/watch_mode/files_watcher.js

@@ -204,6 +204,9 @@ class FilesWatcher extends EventEmitter {
     this.#filteredFiles.clear();
   }
   clear() {
+    clearTimeout(this.#debounceTimer);
+    this.#debounceTimer = null;
+    this.#debounceOwners.clear();
     this.#watchers.forEach(this.#unwatch);
     this.#watchers.clear();
     this.#filteredFiles.clear();

test/parallel/test-watch-mode-files_watcher-clear.mjs

@@ -0,0 +1,69 @@
+// Flags: --expose-internals
+import * as common from '../common/index.mjs';
+import tmpdir from '../common/tmpdir.js';
+import assert from 'node:assert';
+import { writeFileSync } from 'node:fs';
+import { createRequire } from 'node:module';
+
+if (common.isIBMi)
+  common.skip('IBMi does not support `fs.watch()`');
+
+const require = createRequire(import.meta.url);
+const timers = require('node:timers');
+const originalSetTimeout = timers.setTimeout;
+const originalClearTimeout = timers.clearTimeout;
+const { promise, resolve } = Promise.withResolvers();
+const debounce = 1000;
+let debounceTimer;
+let debounceTimerCallback;
+let debounceTimerCleared = false;
+
+timers.setTimeout = function(fn, delay, ...args) {
+  // Only intercept the FilesWatcher debounce timer configured below.
+  if (delay === debounce) {
+    const timer = {
+      __proto__: null,
+      ref() { return this; },
+      unref() { return this; },
+    };
+    debounceTimer = timer;
+    debounceTimerCallback = () => {
+      if (!debounceTimerCleared) {
+        fn(...args);
+      }
+    };
+    resolve();
+    return timer;
+  }
+  return originalSetTimeout(fn, delay, ...args);
+};
+
+timers.clearTimeout = function(timer) {
+  if (timer === debounceTimer) {
+    debounceTimerCleared = true;
+  }
+  return originalClearTimeout(timer);
+};
+
+try {
+  const { FilesWatcher } = require('internal/watch_mode/files_watcher');
+
+  tmpdir.refresh();
+  const file = tmpdir.resolve('watcher-clear.js');
+  writeFileSync(file, '0');
+
+  const watcher = new FilesWatcher({ debounce, mode: 'all' });
+  watcher.on('changed', common.mustNotCall());
+  watcher.watchPath(file, false);
+
+  const interval = setInterval(() => writeFileSync(file, `${Date.now()}`), 50);
+  await promise;
+  clearInterval(interval);
+
+  watcher.clear();
+  assert.strictEqual(debounceTimerCleared, true);
+  debounceTimerCallback();
+} finally {
+  timers.setTimeout = originalSetTimeout;
+  timers.clearTimeout = originalClearTimeout;
+}

test/sequential/test-watch-mode.mjs

@@ -171,6 +171,23 @@ async function failWriteSucceed({ file, watchedFile }) {
 tmpdir.refresh();
 
 describe('watch mode', { concurrency: !process.env.TEST_PARALLEL, timeout: 60_000 }, () => {
+  it('should exit when terminated after the watched process has completed', async () => {
+    const file = createTmpFile();
+    const child = spawn(execPath, ['--watch', '--no-warnings', file], {
+      encoding: 'utf8',
+      stdio: 'pipe',
+    });
+
+    for await (const line of createInterface({ input: child.stdout })) {
+      if (line.includes('Completed running')) {
+        break;
+      }
+    }
+
+    child.kill();
+    await once(child, 'exit');
+  });
+
   it('should watch changes to a file', async () => {
     const file = createTmpFile();
     const { stderr, stdout } = await runWriteSucceed({ file, watchedFile: file, watchFlag: '--watch=true', options: {