[Bug][Regression]: Running two contexts at same time causes firefox to wait endlessly

[fawazahmed0]

Version

1.50.1

Steps to reproduce

const { firefox } = require('playwright');


let browser

async function begin() {
    while (true) {
        browser = await firefox.launch({ headless: true })
        await Promise.all([run(), run()])
        await browser.close()
    }
}

begin()

async function run() {
    let context = await browser.newContext();
    let page = await context.newPage();
    await page.goto('https://playwright.dev/')
    console.log("completed")
}

Expected behavior

Code should continuously print completed

Actual behavior

Code stops printing completed at some point

Additional context

Running two contexts at same time causes the browser to get stuck for eternity

Note: This is regression, the issue does not happen in 1.49.1

Environment

System:
    OS: Windows 11 10.0.22621
    CPU: (6) x64 AMD FX(tm)-6300 Six-Core Processor
    Memory: 12.64 GB / 23.80 GB
  Binaries:
    Node: 23.6.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.9.2 - C:\Program Files\nodejs\npm.CMD
    bun: 1.1.3 - ~\.bun\bin\bun.EXE
  IDEs:
    VSCode: 1.96.4 - C:\Users\nawaz\AppData\Local\Programs\Microsoft VS Code\bin\code.CMD
  npmPackages:
    @playwright/test: ^1.50.1 => 1.50.1
    playwright: ^1.50.1 => 1.50.1
    playwright-extra: ^4.3.6 => 4.3.6

[dgozman]

I can repro this on Windows, but not on macOS. The second concurrent newPage() hangs, with Browser.newPage call never responding and Browser.attachedToTarget never arriving.

[nevercast]

Experiencing this in Github Actions environment but not on my local dev machine. Firefox 134.0 (playwright build v1471) and playwright 1.50.1. Have gone with disable ff e2e for the time being, will consider reverting to 1.49.1 if this will take a while to fix. Thanks for reporting this fawazahmed0.

[aslushnikov]

For the record, the issue can be reproduced with the following minimal example:

import { firefox } from '@playwright/test';

const browser = await firefox.launch({
  executablePath: process.env.FFPATH,
});
const context = await browser.newContext();
await Promise.all([
  context.newPage(),
  context.newPage(),
]);
await browser.close();

This code attempts to create two tabs simultaneously in Firefox, which triggers the following error:

  pw:browser [pid=5108][err] JavaScript error: chrome://browser/content/tabbrowser/tabbrowser.js, line 6485: TypeError: this.selectedBrowser is undefined +24ms
  pw:browser [pid=5108][err] JavaScript error: chrome://juggler/content/TargetRegistry.js, line 150: TypeError: tab.linkedBrowser is undefined +1ms
  pw:browser [pid=5108][err] JavaScript error: chrome://juggler/content/Helper.js, line 82: NS_ERROR_FAILURE: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIWebProgress.removeProgressListener] +13ms

It seems that the following is happening:

1. While tabbrowser is handling the addition of one tab, another tab is being added simultaneously.
2. This triggers the visibilitychanged event in tabbrowser, which causes the following handler to execute:
   https://github.com/mozilla/gecko-dev/blob/a2abcf7ff6b7ae0c2d8a04b9a35679f8c84634e7/browser/components/tabbrowser/content/tabbrowser.js#L6699-L6700
3. However, this handler does not account for the possibility that no browser has been selected yet, leading to a failure this.selectedBrowser is undefined. The thrown exception leaves tabbrowser in an inconsistent state.

[aslushnikov]

I don't have permissions to close issues, but this should've been fixed with the latest firefox roll.