worker: flush stdout and stderr on exit

Signed-off-by: Matteo Collina <hello@matteocollina.com>
PR-URL: #56428
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>

Author: mcollina

lib/internal/bootstrap/switches/is_not_main_thread.js

@@ -31,14 +31,24 @@ process.removeListener('removeListener', stopListeningIfSignal);
 
 const{
  createWorkerStdio,
+ kStdioWantsMoreDataCallback,
 }=require('internal/worker/io');
 
 letworkerStdio;
 functionlazyWorkerStdio(){
-if(!workerStdio)workerStdio=createWorkerStdio();
+if(workerStdio===undefined){
+workerStdio=createWorkerStdio();
+process.on('exit',flushSync);
+}
+
 returnworkerStdio;
 }
 
+functionflushSync(){
+workerStdio.stdout[kStdioWantsMoreDataCallback]();
+workerStdio.stderr[kStdioWantsMoreDataCallback]();
+}
+
 functiongetStdout(){returnlazyWorkerStdio().stdout;}
 
 functiongetStderr(){returnlazyWorkerStdio().stderr;}

lib/internal/worker/io.js

@@ -373,9 +373,13 @@ class WritableWorkerStdio extends Writable {
 chunks: ArrayPrototypeMap(chunks,
 ({ chunk, encoding })=>({ chunk, encoding })),
 });
-ArrayPrototypePush(this[kWritableCallbacks],cb);
-if(this[kPort][kWaitingStreams]++===0)
-this[kPort].ref();
+if(process._exiting){
+cb();
+}else{
+ArrayPrototypePush(this[kWritableCallbacks],cb);
+if(this[kPort][kWaitingStreams]++===0)
+this[kPort].ref();
+}
 }
 
 _final(cb){

test/parallel/test-worker-stdio-flush-inflight.js

@@ -0,0 +1,24 @@
+'use strict';
+constcommon=require('../common');
+constassert=require('assert');
+const{ Worker, isMainThread }=require('worker_threads');
+
+if(isMainThread){
+constw=newWorker(__filename,{stdout: true});
+constexpected='hello world';
+
+letdata='';
+w.stdout.setEncoding('utf8');
+w.stdout.on('data',(chunk)=>{
+data+=chunk;
+});
+
+w.on('exit',common.mustCall(()=>{
+assert.strictEqual(data,expected);
+}));
+}else{
+process.stdout.write('hello');
+process.stdout.write(' ');
+process.stdout.write('world');
+process.exit(0);
+}

test/parallel/test-worker-stdio-flush.js

@@ -0,0 +1,25 @@
+'use strict';
+constcommon=require('../common');
+constassert=require('assert');
+const{ Worker, isMainThread }=require('worker_threads');
+
+if(isMainThread){
+constw=newWorker(__filename,{stdout: true});
+constexpected='hello world';
+
+letdata='';
+w.stdout.setEncoding('utf8');
+w.stdout.on('data',(chunk)=>{
+data+=chunk;
+});
+
+w.on('exit',common.mustCall(()=>{
+assert.strictEqual(data,expected);
+}));
+}else{
+process.on('exit',()=>{
+process.stdout.write(' ');
+process.stdout.write('world');
+});
+process.stdout.write('hello');
+}