test_runner: fix test runner watch mode when no positional arguments

Author: MoLow

src/node_options.cc

@@ -173,7 +173,7 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors,
     } else if (force_repl) {
       errors->push_back("either --watch or --interactive "
                         "can be used, not both");
-    } else if (argv->size() < 1 || (*argv)[1].empty()) {
+    } else if (!test_runner && (argv->size() < 1 || (*argv)[1].empty())) {
       errors->push_back("--watch requires specifying a file");
     }
 

test/parallel/test-runner-watch-mode.mjs

@@ -17,7 +17,7 @@ tmpdir.refresh();
 const fixtureContent = {
   'dependency.js': 'module.exports = {};',
   'dependency.mjs': 'export const a = 1;',
-  'dependent.js': `
+  'test.js': `
 const test = require('node:test');
 require('./dependency.js');
 import('./dependency.mjs');
@@ -29,12 +29,12 @@ const fixturePaths = Object.keys(fixtureContent)
 Object.entries(fixtureContent)
   .forEach(([file, content]) => writeFileSync(fixturePaths[file], content));
 
-async function testWatch({ fileToUpdate }) {
+async function testWatch({ fileToUpdate, file }) {
   const ran1 = util.createDeferredPromise();
   const ran2 = util.createDeferredPromise();
   const child = spawn(process.execPath,
-                      ['--watch', '--test', '--no-warnings', fixturePaths['dependent.js']],
-                      { encoding: 'utf8', stdio: 'pipe' });
+                      ['--watch', '--test', file ? fixturePaths[file] : undefined].filter(Boolean),
+                      { encoding: 'utf8', stdio: 'pipe', cwd: tmpdir.path });
   let stdout = '';
 
   child.stdout.on('data', (data) => {
@@ -47,25 +47,26 @@ async function testWatch({ fileToUpdate }) {
   await ran1.promise;
   const content = fixtureContent[fileToUpdate];
   const path = fixturePaths[fileToUpdate];
-  const interval = setInterval(() => {
-    console.log(`Updating ${path}`);
-    writeFileSync(path, content);
-  }, 50);
+  const interval = setInterval(() => writeFileSync(path, content), 50);
   await ran2.promise;
   clearInterval(interval);
   child.kill();
 }
 
 describe('test runner watch mode', () => {
   it('should run tests repeatedly', async () => {
-    await testWatch({ fileToUpdate: 'dependent.js' });
+    await testWatch({ file: 'test.js', fileToUpdate: 'test.js' });
   });
 
   it('should run tests with dependency repeatedly', async () => {
-    await testWatch({ fileToUpdate: 'dependency.js' });
+    await testWatch({ file: 'test.js', fileToUpdate: 'dependency.js' });
   });
 
   it('should run tests with ESM dependency', async () => {
-    await testWatch({ fileToUpdate: 'dependency.mjs' });
+    await testWatch({ file: 'test.js', fileToUpdate: 'dependency.mjs' });
+  });
+
+  it('should support running tests without a file', async () => {
+    await testWatch({ fileToUpdate: 'test.js' });
   });
 });