chore(test runner): self profile under PWTEST_PROFILE_DIR (#7252)

`PWTEST_CLI_ALLOW_TEST_COMMAND=1 PWTEST_PROFILE_DIR=./profile node lib/cli/cli.js test -c <dir/config>`

src/test/cli.ts

@@ -21,6 +21,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import type { Config } from './types';
 import { Runner } from './runner';
+import { stopProfiling, startProfiling } from './profiler';
 
 const defaultTimeout = 30000;
 const defaultReporter = process.env.CI ? 'dot' : 'list';
@@ -80,6 +81,8 @@ export function addTestCommand(program: commander.CommanderStatic) {
 }
 
 async function runTests(args: string[], opts: { [key: string]: any }) {
+  await startProfiling();
+
   const browserOpt = opts.browser ? opts.browser.toLowerCase() : 'chromium';
   if (!['all', 'chromium', 'firefox', 'webkit'].includes(browserOpt))
     throw new Error(`Unsupported browser "${opts.browser}", must be one of "all", "chromium", "firefox" or "webkit"`);
@@ -129,6 +132,8 @@ async function runTests(args: string[], opts: { [key: string]: any }) {
   }
 
   const result = await runner.run(!!opts.list, args.map(forceRegExp), opts.project || undefined);
+  await stopProfiling(undefined);
+
   if (result === 'sigint')
     process.exit(130);
   process.exit(result === 'passed' ? 0 : 1);

src/test/profiler.ts

@@ -0,0 +1,48 @@
+/**
+ * Copyright Microsoft Corporation. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+
+const profileDir = process.env.PWTEST_PROFILE_DIR || '';
+
+let session: import('inspector').Session;
+
+export async function startProfiling() {
+  if (!profileDir)
+    return;
+
+  session = new (require('inspector').Session)();
+  session.connect();
+  await new Promise<void>(f => {
+    session.post('Profiler.enable', () => {
+      session.post('Profiler.start', f);
+    });
+  });
+}
+
+export async function stopProfiling(workerIndex: number | undefined) {
+  if (!profileDir)
+    return;
+
+  await new Promise<void>(f => session.post('Profiler.stop', async (err, { profile }) => {
+    if (!err) {
+      await fs.promises.mkdir(profileDir, { recursive: true });
+      await fs.promises.writeFile(path.join(profileDir, workerIndex === undefined ? 'runner.json' : 'worker' + workerIndex + '.json'), JSON.stringify(profile));
+    }
+    f();
+  }));
+}

src/test/worker.ts

@@ -17,6 +17,7 @@
 import { Console } from 'console';
 import * as util from 'util';
 import { RunPayload, TestOutputPayload, WorkerInitParams } from './ipc';
+import { startProfiling, stopProfiling } from './profiler';
 import { serializeError } from './util';
 import { WorkerRunner } from './workerRunner';
 
@@ -55,6 +56,7 @@ process.on('SIGINT',() => {});
 process.on('SIGTERM',() => {});
 
 let workerRunner: WorkerRunner;
+let workerIndex: number | undefined;
 
 process.on('unhandledRejection', (reason, promise) => {
   if (workerRunner)
@@ -69,6 +71,8 @@ process.on('uncaughtException', error => {
 process.on('message', async message => {
   if (message.method === 'init') {
     const initParams = message.params as WorkerInitParams;
+    workerIndex = initParams.workerIndex;
+    startProfiling();
     workerRunner = new WorkerRunner(initParams);
     for (const event of ['testBegin', 'testEnd', 'done'])
       workerRunner.on(event, sendMessageToParent.bind(null, event));
@@ -96,6 +100,8 @@ async function gracefullyCloseAndExit() {
       workerRunner.stop();
       await workerRunner.cleanup();
     }
+    if (workerIndex !== undefined)
+      await stopProfiling(workerIndex);
   } catch (e) {
     process.send!({ method: 'teardownError', params: { error: serializeError(e) } });
   }