chore: pick session to attach from env (microsoft#39650)

Author: pavelfeldman

packages/playwright-core/src/tools/cli-client/program.ts

@@ -344,17 +344,26 @@ async function listSessions(registry: Registry, clientInfo: ClientInfo, all: boo
       return;
     }
 
+    const runningSessions = new Set<string>();
     if (entries.size)
       console.log('### Browsers');
     for (const [workspace, list] of entries)
-      await gcAndPrintSessions(clientInfo, list.map(entry => new Session(entry)), `${path.relative(process.cwd(), workspace) || '/'}:`);
+      await gcAndPrintSessions(clientInfo, list.map(entry => new Session(entry)), `${path.relative(process.cwd(), workspace) || '/'}:`, runningSessions);
+
+    // Filter out server entries that already have an attached session.
+    const filteredServerEntries = new Map<string, BrowserDescriptor[]>();
+    for (const [workspace, list] of serverEntries) {
+      const unattached = list.filter(d => !runningSessions.has(d.title));
+      if (unattached.length)
+        filteredServerEntries.set(workspace, unattached);
+    }
 
-    if (serverEntries.size) {
+    if (filteredServerEntries.size) {
       if (entries.size)
         console.log('');
       console.log('### Browser servers available for attach');
     }
-    for (const [workspace, list] of serverEntries)
+    for (const [workspace, list] of filteredServerEntries)
       await gcAndPrintBrowserSessions(workspace, list);
   } else {
     console.log('### Browsers');
@@ -363,14 +372,15 @@ async function listSessions(registry: Registry, clientInfo: ClientInfo, all: boo
   }
 }
 
-async function gcAndPrintSessions(clientInfo: ClientInfo, sessions: Session[], header?: string) {
+async function gcAndPrintSessions(clientInfo: ClientInfo, sessions: Session[], header?: string, runningSessions?: Set<string>) {
   const running: Session[] = [];
   const stopped: Session[] = [];
 
   for (const session of sessions) {
     const canConnect = await session.canConnect();
     if (canConnect) {
       running.push(session);
+      runningSessions?.add(session.name);
     } else {
       if (session.config.cli.persistent)
         stopped.push(session);

packages/playwright-core/src/tools/cli-client/session.ts

@@ -147,8 +147,8 @@ export class Session {
       args.push(`--profile=${cliArgs.profile}`);
     if (cliArgs.config)
       args.push(`--config=${cliArgs.config}`);
-    if (cliArgs.attach)
-      args.push(`--attach=${cliArgs.attach}`);
+    if (cliArgs.attach || process.env.PLAYWRIGHT_CLI_SESSION)
+      args.push(`--attach=${cliArgs.attach || process.env.PLAYWRIGHT_CLI_SESSION}`);
 
     const child = spawn(process.execPath, args, {
       detached: true,

tests/mcp/cli-session.spec.ts

@@ -332,6 +332,26 @@ workspace1:
     expect(error).toContain('Error: unable to connect to a browser that does not have any contexts');
   });
 
+  test('attach via PLAYWRIGHT_CLI_SESSION env', async ({ cli, mcpBrowser }) => {
+    const browserName = mcpBrowser.replace('chrome', 'chromium');
+    await using browser = await playwright[browserName].launch({ headless: true });
+    const page = await browser.newPage();
+    await page.setContent('<title>Env Page</title><h1>Hello from env</h1>');
+    await (browser as any)._register('foobar', { workspaceDir: 'workspace1' });
+    const { output: openOutput, snapshot } = await cli('open', { env: { PLAYWRIGHT_CLI_SESSION: 'foobar' } });
+    expect(openOutput).toContain('### Browser `foobar` opened with pid');
+    expect(openOutput).toContain('Env Page');
+    expect(snapshot).toContain('Hello from env');
+    const { output: listOutput } = await cli('list', '--all');
+    expect(listOutput).toBe(`### Browsers
+/:
+- foobar:
+  - status: open
+  - browser-type: ${mcpBrowser.replace('chrome', 'chromium')}
+  - user-data-dir: <in-memory>
+  - headed: true`);
+  });
+
   test('detach from browser server', async ({ cli, mcpBrowser }) => {
     const browserName = mcpBrowser.replace('chrome', 'chromium');
     await using browser = await playwright[browserName].launch({ headless: true });