test_runner: emit test:watch:drained event

PR-URL: #48259
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

Author: MoLow

doc/api/test.md

@@ -1473,6 +1473,10 @@ This event is only emitted if `--test` flag is passed.
 Emitted when a running test writes to `stdout`.
 This event is only emitted if `--test` flag is passed.
 
+### Event: `'test:watch:drained'`
+
+Emitted when no more tests are queued for execution in watch mode.
+
 ## Class: `TestContext`
 
 <!-- YAML

lib/internal/test_runner/runner.js

@@ -341,25 +341,25 @@ class FileTest extends Test {
 }
 }
 
-construnningProcesses=newSafeMap();
-construnningSubtests=newSafeMap();
-
 functionrunTestFile(path,root,inspectPort,filesWatcher,testNamePatterns){
+constwatchMode=filesWatcher!=null;
 constsubtest=root.createSubtest(FileTest,path,async(t)=>{
 constargs=getRunArgs({ path, inspectPort, testNamePatterns });
 conststdio=['pipe','pipe','pipe'];
 constenv={ ...process.env,NODE_TEST_CONTEXT: 'child-v8'};
-if(filesWatcher){
+if(watchMode){
 stdio.push('ipc');
 env.WATCH_REPORT_DEPENDENCIES='1';
 }
 
 constchild=spawn(process.execPath,args,{signal: t.signal,encoding: 'utf8', env, stdio });
-runningProcesses.set(path,child);
+if(watchMode){
+filesWatcher.runningProcesses.set(path,child);
+filesWatcher.watcher.watchChildProcessModules(child,path);
+}
 
 leterr;
 
-filesWatcher?.watchChildProcessModules(child,path);
 
 child.on('error',(error)=>{
 err=error;
@@ -391,8 +391,14 @@ function runTestFile(path, root, inspectPort, filesWatcher, testNamePatterns) {
 finished(child.stdout,{signal: t.signal}),
 ]);
 
-runningProcesses.delete(path);
-runningSubtests.delete(path);
+if(watchMode){
+filesWatcher.runningProcesses.delete(path);
+filesWatcher.runningSubtests.delete(path);
+if(filesWatcher.runningSubtests.size===0){
+root.reporter[kEmitMessage]('test:watch:drained');
+}
+}
+
 if(code!==0||signal!==null){
 if(!err){
 constfailureType=subtest.failedSubtests ? kSubtestsFailed : kTestCodeFailure;
@@ -413,9 +419,13 @@ function runTestFile(path, root, inspectPort, filesWatcher, testNamePatterns) {
 }
 
 functionwatchFiles(testFiles,root,inspectPort,signal,testNamePatterns){
-constfilesWatcher=newFilesWatcher({throttle: 500,mode: 'filter', signal });
-filesWatcher.on('changed',({ owners })=>{
-filesWatcher.unfilterFilesOwnedBy(owners);
+construnningProcesses=newSafeMap();
+construnningSubtests=newSafeMap();
+constwatcher=newFilesWatcher({throttle: 500,mode: 'filter', signal });
+constfilesWatcher={__proto__: null, watcher, runningProcesses, runningSubtests };
+
+watcher.on('changed',({ owners })=>{
+watcher.unfilterFilesOwnedBy(owners);
 PromisePrototypeThen(SafePromiseAllReturnVoid(testFiles,async(file)=>{
 if(!owners.has(file)){
 return;
@@ -436,6 +446,7 @@ function watchFiles(testFiles, root, inspectPort, signal, testNamePatterns) {
 }));
 });
 signal?.addEventListener('abort',()=>root.postRun(),{__proto__: null,once: true});
+
 returnfilesWatcher;
 }
 
@@ -485,7 +496,7 @@ function run(options) {
 root.harness.bootstrapComplete=true;
 returnSafePromiseAllSettledReturnVoid(testFiles,(path)=>{
 constsubtest=runTestFile(path,root,inspectPort,filesWatcher,testNamePatterns);
-runningSubtests.set(path,subtest);
+filesWatcher?.runningSubtests.set(path,subtest);
 returnsubtest;
 });
 };

test/parallel/test-runner-run.mjs

@@ -132,4 +132,14 @@ describe('require(\'node:test\').run', { concurrency: true }, () => {
 .toArray();
 assert.deepStrictEqual(result,['this should pass']);
 });
+
+it('should emit "test:watch:drained" event on watch mode',async()=>{
+constcontroller=newAbortController();
+awaitrun({files: [join(testFixtures,'test/random.cjs')],watch: true,signal: controller.signal})
+.on('data',function({ type }){
+if(type==='test:watch:drained'){
+controller.abort();
+}
+});
+});
 });