[BUG] Electron: race condition with firstWindow and loadURL, will hang forever

[Prinzhorn]

Context:

• Playwright Version: 1.26.1
• Operating System: Linux (Ubuntu 22.04)
• Node.js version: 16.15.1
• Browser: Electron 21.0.1

Code Snippet

test.js

import { _electron as electron } from 'playwright';

(async () => {
  const app = await electron.launch({ args: ['main.cjs'] });

  console.log('trying to get window...');

  await app.firstWindow();

  console.log('got window');
})();

main.cjs

const { app, BrowserWindow } = require('electron');

let mainWindow;

function createWindow() {
  mainWindow = new BrowserWindow({
    width: 800,
    height: 600,
  });

  setTimeout(() => {
    mainWindow.loadURL('https://www.example.com/');
  }, 1000);
}

app.whenReady().then(() => {
  createWindow();
});

Describe the bug

The above will forever hang at trying to get window.... Lowering the setTimeout will eventually make it work. E.g. 20ms will sometimes work and give got window.

I'm running into this because here's what my app does:

1. Instantly open the window, so you immediately get feedback that the app is starting
2. Launch an HTTP server on localhost
3. Once the server is up, call loadURL with the localhost URL including the randomly assigned port

Playwright does not work with this setup, because it essentially requires loadURL to be called roughly immediately after creating the window.

[Prinzhorn]

A workaround seems to be to synchronously call mainWindow.loadURL('about:blank'); after creating the window. But I'm not sure about the implications this might have, it should not be necessary.

[yury-s]

This is a regression. The example works in v13.4.0 and hangs in v14.2.9.

[mxschmitt]

Was able to create a smaller repro out of it see here and linked it upstream.