test: fix flaky test-watch-mode-kill-signal-*

After the write triggers a restart of the grandchild, the newly
spawned second grandchild can post another 'script ready' message
before the stdout from the first grandchild is relayed by the
watcher and processed by this parent process to kill
the watcher. If we write again and trigger another restart, we can
end up in an infinite loop and never receive the stdout of the
grandchildren in time.
Only write once to verify the first grandchild process receives
the expected signal. We don't care about the subsequent grandchild
processes.

PR-URL: https://github.com/nodejs/node/pull/60443
Refs: https://github.com/nodejs/node/issues/60297
Refs: https://github.com/nodejs/node/pull/60391
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

test/fixtures/kill-signal-for-watch.js

@@ -1,4 +1,10 @@
-process.on('SIGTERM', () => { console.log('__SIGTERM received__'); process.exit(); });
-process.on('SIGINT', () => { console.log('__SIGINT received__'); process.exit(); });
-process.send('script ready');
+process.on('SIGTERM', () => {
+  console.log(`__SIGTERM received__ ${process.pid}`);
+  process.exit();
+});
+process.on('SIGINT', () => {
+  console.log(`__SIGINT received__ ${process.pid}`);
+  process.exit();
+});
+process.send(`script ready ${process.pid}`);
 setTimeout(() => {}, 100_000);

test/parallel/test-watch-mode-kill-signal-default.mjs

@@ -26,20 +26,37 @@ const child = spawn(
 );
 
 let stdout = '';
+let firstGrandchildPid;
 child.stdout.on('data', (data) => {
-  stdout += `${data}`;
-  if (/__(SIGINT|SIGTERM) received__/.test(stdout)) {
+  const dataStr = data.toString();
+  console.log(`[STDOUT] ${dataStr}`);
+  stdout += `${dataStr}`;
+  const match = dataStr.match(/__(SIGINT|SIGTERM) received__ (\d+)/);
+  if (match && match[2] === firstGrandchildPid) {
+    console.log(`[PARENT] Sending kill signal to watcher process: ${child.pid}`);
     child.kill();
   }
 });
 
+// After the write triggers a restart of the grandchild, the newly spawned second
+// grandchild can post another 'script ready' message before the stdout from the first
+// grandchild is relayed by the watcher and processed by this parent process to kill
+// the watcher. If we write again and trigger another restart, we can
+// end up in an infinite loop and never receive the stdout of the grandchildren in time.
+// Only write once to verify the first grandchild process receives the expected signal.
+// We don't care about the subsequent grandchild processes.
 child.on('message', (msg) => {
-  if (msg === 'script ready') {
+  console.log(`[MESSAGE]`, msg);
+  if (!firstGrandchildPid && typeof msg === 'string') {
+    const match = msg.match(/script ready (\d+)/);
+    if (match) {
+      firstGrandchildPid = match[1];  // This is the first grandchild
       writeFileSync(indexPath, indexContents);
     }
+  }
 });
 
 await once(child, 'exit');
 
-assert.match(stdout, /__SIGTERM received__/);
-assert.doesNotMatch(stdout, /__SIGINT received__/);
+assert.match(stdout, new RegExp(`__SIGTERM received__ ${firstGrandchildPid}`));
+assert.doesNotMatch(stdout, new RegExp(`__SIGINT received__ ${firstGrandchildPid}`));

test/parallel/test-watch-mode-kill-signal-override.mjs

@@ -27,20 +27,40 @@ const child = spawn(
 );
 
 let stdout = '';
+let firstGrandchildPid;
 child.stdout.on('data', (data) => {
-  stdout += `${data}`;
-  if (/__(SIGINT|SIGTERM) received__/.test(stdout)) {
+  const dataStr = data.toString();
+  console.log(`[STDOUT] ${dataStr}`);
+  stdout += `${dataStr}`;
+  const match = dataStr.match(/__(SIGINT|SIGTERM) received__ (\d+)/);
+  if (match && match[2] === firstGrandchildPid) {
+    console.log(`[PARENT] Sending kill signal to watcher process: ${child.pid}`);
     child.kill();
   }
 });
 
+// After the write triggers a restart of the grandchild, the newly spawned second
+// grandchild can post another 'script ready' message before the stdout from the first
+// grandchild is relayed by the watcher and processed by this parent process to kill
+// the watcher. If we write again and trigger another restart, we can
+// end up in an infinite loop and never receive the stdout of the grandchildren in time.
+// Only write once to verify the first grandchild process receives the expected signal.
+// We don't care about the subsequent grandchild processes.
 child.on('message', (msg) => {
-  if (msg === 'script ready') {
+  console.log(`[MESSAGE]`, msg);
+  if (!firstGrandchildPid && typeof msg === 'string') {
+    const match = msg.match(/script ready (\d+)/);
+    if (match) {
+      firstGrandchildPid = match[1];  // This is the first grandchild
       writeFileSync(indexPath, indexContents);
     }
+  }
 });
 
 await once(child, 'exit');
 
-assert.match(stdout, /__SIGINT received__/);
-assert.doesNotMatch(stdout, /__SIGTERM received__/);
+// The second grandchild, if there is one, could receive SIGTERM if it's killed as a
+// consequence of the parent being killed in this process instead of being killed by the
+// parent for file changes. Here we only care about the first grandchild.
+assert.match(stdout, new RegExp(`__SIGINT received__ ${firstGrandchildPid}`));
+assert.doesNotMatch(stdout, new RegExp(`__SIGTERM received__ ${firstGrandchildPid}`));