chore: do not use experimental loader for web server (#16733)

packages/playwright-test/src/cli.ts

@@ -241,7 +241,7 @@ function restartWithExperimentalTsEsm(configFile: string | null): boolean {
     return false;
   if (!fileIsModule(configFile))
     return false;
-  const NODE_OPTIONS = (process.env.NODE_OPTIONS || '') + ` --experimental-loader=${url.pathToFileURL(require.resolve('@playwright/test/lib/experimentalLoader')).toString()}`;
+  const NODE_OPTIONS = (process.env.NODE_OPTIONS || '') + experimentalLoaderOption();
   const innerProcess = require('child_process').fork(require.resolve('playwright-core/cli'), process.argv.slice(2), {
     env: {
       ...process.env,
@@ -257,4 +257,16 @@ function restartWithExperimentalTsEsm(configFile: string | null): boolean {
   return true;
 }
 
+export function experimentalLoaderOption() {
+  return ` --experimental-loader=${url.pathToFileURL(require.resolve('@playwright/test/lib/experimentalLoader')).toString()}`;
+}
+
+export function envWithoutExperimentalLoaderOptions(): NodeJS.ProcessEnv {
+  const substring = experimentalLoaderOption();
+  const result = { ...process.env };
+  if (result.NODE_OPTIONS)
+    result.NODE_OPTIONS = result.NODE_OPTIONS.replace(substring, '').trim() || undefined;
+  return result;
+}
+
 const kTraceModes: TraceMode[] = ['on', 'off', 'on-first-retry', 'retain-on-failure'];

packages/playwright-test/src/plugins/webServerPlugin.ts

@@ -25,6 +25,7 @@ import { launchProcess } from 'playwright-core/lib/utils/processLauncher';
 import type { FullConfig, Reporter } from '../../types/testReporter';
 import type { TestRunnerPlugin } from '.';
 import type { FullConfigInternal } from '../types';
+import { envWithoutExperimentalLoaderOptions } from '../cli';
 
 
 export type WebServerPluginOptions = {
@@ -91,7 +92,7 @@ export class WebServerPlugin implements TestRunnerPlugin {
       command: this._options.command,
       env: {
         ...DEFAULT_ENVIRONMENT_VARIABLES,
-        ...process.env,
+        ...envWithoutExperimentalLoaderOptions(),
         ...this._options.env,
       },
       cwd: this._options.cwd,
@@ -99,7 +100,7 @@ export class WebServerPlugin implements TestRunnerPlugin {
       shell: true,
       attemptToGracefullyClose: async () => {},
       log: () => {},
-      onExit: code => processExitedReject(new Error(`Process from config.webServer was not able to start. Exit code: ${code}`)),
+      onExit: code => processExitedReject(new Error(code ? `Process from config.webServer was not able to start. Exit code: ${code}` : 'Process from config.webServer exited early.')),
       tempDirectories: [],
     });
     this._killProcess = kill;

tests/playwright-test/loader.spec.ts

@@ -418,3 +418,34 @@ test('should work with cross-imports - 2', async ({ runInlineTest }) => {
   expect(result.output).toContain('TEST-1');
   expect(result.output).toContain('TEST-2');
 });
+
+test('should load web server w/o esm loader in ems module', async ({ runInlineTest, nodeVersion }) => {
+  // We only support experimental esm mode on Node 16+
+  test.skip(nodeVersion.major < 16);
+  const result = await runInlineTest({
+    'playwright.config.ts': `
+      //@no-header
+      export default {
+        webServer: {
+          command: 'node ws.js',
+          port: 9876,
+          timeout: 100,
+        },
+        projects: [{name: 'foo'}]
+      }`,
+    'package.json': `{ "type": "module" }`,
+    'ws.js': `
+      //@no-header
+      console.log('NODE_OPTIONS ' + process.env.NODE_OPTIONS);
+      setTimeout(() => {}, 100000);
+    `,
+    'a.test.ts': `
+      const { test } = pwt;
+      test('passes', () => {});
+    `
+  }, {}, { ...process.env, DEBUG: 'pw:webserver' });
+
+  expect(result.exitCode).toBe(1);
+  expect(result.passed).toBe(0);
+  expect(result.output).toContain('NODE_OPTIONS undefined');
+});