Fix race condition bug in session file check

Co-authored-by: pavelfeldman <883973+pavelfeldman@users.noreply.github.com>

README.md

@@ -164,6 +164,8 @@ Playwright MCP server supports following arguments. They can be provided in the
                                "http://myproxy:3128" or "socks5://myproxy:8080"
   --save-trace                 Whether to save the Playwright Trace of the
                                session into the output directory.
+  --save-session               Whether to save the session log with tool calls
+                               and snapshots into the output directory.
   --storage-state <path>       path to the storage state file for isolated
                                sessions.
   --user-agent <ua string>     specify user agent string

config.d.ts

@@ -90,6 +90,11 @@ export type Config = {
    */
   saveTrace?: boolean;
 
+  /**
+   * Whether to save the session log with tool calls and snapshots into the output directory.
+   */
+  saveSession?: boolean;
+
   /**
    * The directory to save output files.
    */

src/config.ts

@@ -44,6 +44,7 @@ export type CLIOptions = {
   proxyBypass?: string;
   proxyServer?: string;
   saveTrace?: boolean;
+  saveSession?: boolean;
   storageState?: string;
   userAgent?: string;
   userDataDir?: string;
@@ -191,6 +192,7 @@ export function configFromCLIOptions(cliOptions: CLIOptions): Config {
       blockedOrigins: cliOptions.blockedOrigins,
     },
     saveTrace: cliOptions.saveTrace,
+    saveSession: cliOptions.saveSession,
     outputDir: cliOptions.outputDir,
     imageResponses: cliOptions.imageResponses,
   };
@@ -221,6 +223,7 @@ function configFromEnv(): Config {
   options.proxyBypass = envToString(process.env.PLAYWRIGHT_MCP_PROXY_BYPASS);
   options.proxyServer = envToString(process.env.PLAYWRIGHT_MCP_PROXY_SERVER);
   options.saveTrace = envToBoolean(process.env.PLAYWRIGHT_MCP_SAVE_TRACE);
+  options.saveSession = envToBoolean(process.env.PLAYWRIGHT_MCP_SAVE_SESSION);
   options.storageState = envToString(process.env.PLAYWRIGHT_MCP_STORAGE_STATE);
   options.userAgent = envToString(process.env.PLAYWRIGHT_MCP_USER_AGENT);
   options.userDataDir = envToString(process.env.PLAYWRIGHT_MCP_USER_DATA_DIR);

src/context.ts

@@ -16,6 +16,8 @@
 
 import debug from 'debug';
 import * as playwright from 'playwright';
+import * as fs from 'fs';
+import * as path from 'path';
 
 import { callOnPageNoTrace, waitForCompletion } from './tools/utils.js';
 import { ManualPromise } from './manualPromise.js';
@@ -42,6 +44,8 @@ export class Context {
   private _modalStates: (ModalState & { tab: Tab })[] = [];
   private _pendingAction: PendingAction | undefined;
   private _downloads: { download: playwright.Download, finished: boolean, outputFile: string }[] = [];
+  private _sessionFile: string | undefined;
+  private _sessionFileInitialized: Promise<void> | undefined;
   clientVersion: { name: string; version: string; } | undefined;
 
   constructor(tools: Tool[], config: FullConfig, browserContextFactory: BrowserContextFactory) {
@@ -49,6 +53,8 @@ export class Context {
     this.config = config;
     this._browserContextFactory = browserContextFactory;
     testDebug('create context');
+    if (this.config.saveSession)
+      this._sessionFileInitialized = this._initializeSessionFile();
   }
 
   clientSupportsImages(): boolean {
@@ -129,6 +135,50 @@ export class Context {
     return await this.listTabsMarkdown();
   }
 
+  private async _initializeSessionFile() {
+    if (!this.config.saveSession)
+      return;
+
+    const timestamp = new Date().toISOString();
+    const fileName = `session${timestamp}.yml`;
+    this._sessionFile = await outputFile(this.config, fileName);
+
+    // Initialize empty session file
+    await fs.promises.writeFile(this._sessionFile, '# Session log started at ' + timestamp + '\n', 'utf8');
+  }
+
+  private async _logSessionEntry(toolName: string, params: Record<string, unknown>, snapshotFile?: string) {
+    if (!this.config.saveSession)
+      return;
+
+    // Ensure session file is initialized before proceeding
+    if (this._sessionFileInitialized)
+      await this._sessionFileInitialized;
+
+    // After initialization, session file should always be defined when saveSession is true
+    if (!this._sessionFile)
+      throw new Error('Session file not initialized despite saveSession being enabled');
+
+    const entry = [
+      `- ${toolName}:`,
+      '    params:',
+    ];
+
+    // Add parameters with proper YAML indentation
+    for (const [key, value] of Object.entries(params)) {
+      const yamlValue = typeof value === 'string' ? value : JSON.stringify(value);
+      entry.push(`      ${key}: ${yamlValue}`);
+    }
+
+    // Add snapshot reference if provided
+    if (snapshotFile)
+      entry.push(`    snapshot: ${path.basename(snapshotFile)}`);
+
+    entry.push(''); // Empty line for readability
+
+    await fs.promises.appendFile(this._sessionFile, entry.join('\n') + '\n', 'utf8');
+  }
+
   async run(tool: Tool, params: Record<string, unknown> | undefined) {
     // Tab management is done outside of the action() call.
     const toolResult = await tool.handle(this, tool.schema.inputSchema.parse(params || {}));
@@ -147,6 +197,8 @@ export class Context {
     }
 
     const tab = this.currentTabOrDie();
+    let snapshotFile: string | undefined;
+
     // TODO: race against modal dialogs to resolve clicks.
     const actionResult = await this._raceAgainstModalDialogs(async () => {
       try {
@@ -155,11 +207,23 @@ export class Context {
         else
           return await action?.() ?? undefined;
       } finally {
-        if (captureSnapshot && !this._javaScriptBlocked())
+        if (captureSnapshot && !this._javaScriptBlocked()) {
           await tab.captureSnapshot();
+          // Save snapshot to file if session logging is enabled
+          if (this.config.saveSession && tab.hasSnapshot()) {
+            const timestamp = new Date().toISOString();
+            const snapshotFileName = `${timestamp}.snapshot.yaml`;
+            snapshotFile = await outputFile(this.config, snapshotFileName);
+            await fs.promises.writeFile(snapshotFile, tab.snapshotOrDie().text(), 'utf8');
+          }
+        }
       }
     });
 
+    // Log session entry if enabled
+    if (this.config.saveSession)
+      await this._logSessionEntry(tool.schema.name, params || {}, snapshotFile);
+
     const result: string[] = [];
     result.push(`### Ran Playwright code
 \`\`\`js

src/program.ts

@@ -47,6 +47,7 @@ program
     .option('--proxy-bypass <bypass>', 'comma-separated domains to bypass proxy, for example ".com,chromium.org,.domain.com"')
     .option('--proxy-server <proxy>', 'specify proxy server, for example "http://myproxy:3128" or "socks5://myproxy:8080"')
     .option('--save-trace', 'Whether to save the Playwright Trace of the session into the output directory.')
+    .option('--save-session', 'Whether to save the session log with tool calls and snapshots into the output directory.')
     .option('--storage-state <path>', 'path to the storage state file for isolated sessions.')
     .option('--user-agent <ua string>', 'specify user agent string')
     .option('--user-data-dir <path>', 'path to the user data directory. If not specified, a temporary directory will be created.')

tests/session.spec.ts

@@ -0,0 +1,78 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * 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 fs from 'fs';
+import path from 'path';
+
+import { test, expect } from './fixtures.js';
+
+test('check that session is saved', async ({ startClient, server, mcpMode }, testInfo) => {
+  const outputDir = testInfo.outputPath('output');
+
+  const { client } = await startClient({
+    args: ['--save-session', `--output-dir=${outputDir}`],
+  });
+
+  expect(await client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  })).toContainTextContent(`Navigate to http://localhost`);
+
+  // Check that session file exists
+  const files = fs.readdirSync(outputDir);
+  const sessionFiles = files.filter(f => f.startsWith('session') && f.endsWith('.yml'));
+  expect(sessionFiles.length).toBe(1);
+
+  // Check session file content
+  const sessionContent = fs.readFileSync(path.join(outputDir, sessionFiles[0]), 'utf8');
+  expect(sessionContent).toContain('- browser_navigate:');
+  expect(sessionContent).toContain('params:');
+  expect(sessionContent).toContain('url: ' + server.HELLO_WORLD);
+  expect(sessionContent).toContain('snapshot:');
+});
+
+test('check that session includes multiple tool calls', async ({ startClient, server, mcpMode }, testInfo) => {
+  const outputDir = testInfo.outputPath('output');
+
+  const { client } = await startClient({
+    args: ['--save-session', `--output-dir=${outputDir}`],
+  });
+
+  // Navigate to a page
+  await client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.HELLO_WORLD },
+  });
+
+  // Take a snapshot
+  await client.callTool({
+    name: 'browser_snapshot',
+    arguments: {},
+  });
+
+  // Check that session file exists and contains both calls
+  const files = fs.readdirSync(outputDir);
+  const sessionFiles = files.filter(f => f.startsWith('session') && f.endsWith('.yml'));
+  expect(sessionFiles.length).toBe(1);
+
+  const sessionContent = fs.readFileSync(path.join(outputDir, sessionFiles[0]), 'utf8');
+  expect(sessionContent).toContain('- browser_navigate:');
+  expect(sessionContent).toContain('- browser_snapshot:');
+
+  // Check that snapshot files exist
+  const snapshotFiles = files.filter(f => f.includes('snapshot.yaml'));
+  expect(snapshotFiles.length).toBeGreaterThan(0);
+});