fix: move window.open postMessage test to main runner to fix flake (#18735)

spec-main/chromium-spec.ts

@@ -1,7 +1,8 @@
 import * as chai from 'chai'
 import * as chaiAsPromised from 'chai-as-promised'
-import { BrowserWindow, session } from 'electron'
+import { BrowserWindow, session, ipcMain } from 'electron'
 import { emittedOnce } from './events-helpers';
+import { closeAllWindows } from './window-helpers';
 import * as https from 'https';
 import * as path from 'path';
 import * as fs from 'fs';
@@ -70,3 +71,19 @@ describe('reporting api', () => {
     }
   })
 })
+
+describe('window.postMessage', () => {
+  afterEach(async () => {
+    await closeAllWindows()
+  })
+
+  it('sets the source and origin correctly', async () => {
+    const w = new BrowserWindow({show: false, webPreferences: {nodeIntegration: true}})
+    w.loadURL(`file://${fixturesPath}/pages/window-open-postMessage-driver.html`)
+    const [, message] = await emittedOnce(ipcMain, 'complete')
+    expect(message.data).to.equal('testing')
+    expect(message.origin).to.equal('file://')
+    expect(message.sourceEqualsOpener).to.equal(true)
+    expect(message.eventOrigin).to.equal('file://')
+  })
+})

spec-main/window-helpers.ts

@@ -39,3 +39,9 @@ export const closeWindow = async (
     }
   }
 }
+
+export async function closeAllWindows() {
+  for (const w of BrowserWindow.getAllWindows()) {
+    await closeWindow(w, {assertNotWindows: false})
+  }
+}

spec/chromium-spec.js

@@ -721,27 +721,6 @@ describe('chromium feature', () => {
   })
 
   describe('window.postMessage', () => {
-    it('sets the source and origin correctly', (done) => {
-      let b = null
-      listener = (event) => {
-        window.removeEventListener('message', listener)
-        b.close()
-        const message = JSON.parse(event.data)
-        expect(message.data).to.equal('testing')
-        expect(message.origin).to.equal('file://')
-        expect(message.sourceEqualsOpener).to.be.true()
-        expect(event.origin).to.equal('file://')
-        done()
-      }
-      window.addEventListener('message', listener)
-      app.once('browser-window-created', (event, { webContents }) => {
-        webContents.once('did-finish-load', () => {
-          b.postMessage('testing', '*')
-        })
-      })
-      b = window.open(`file://${fixtures}/pages/window-open-postMessage.html`, '', 'show=no')
-    })
-
     it('throws an exception when the targetOrigin cannot be converted to a string', () => {
       const b = window.open('')
       expect(() => {

spec/fixtures/pages/window-open-postMessage-driver.html

@@ -0,0 +1,10 @@
+<script>
+  const child = window.open(`./window-open-postMessage.html`, '', 'show=no')
+  window.onmessage = (e) => {
+    if (e.data === 'ready') {
+      child.postMessage('testing', '*')
+    } else {
+      require('electron').ipcRenderer.send('complete', {eventOrigin: e.origin, ...JSON.parse(e.data)})
+    }
+  }
+</script>

spec/fixtures/pages/window-open-postMessage.html

@@ -8,6 +8,7 @@
       sourceEqualsOpener: e.source === window.opener
     }), '*');
   });
+  window.opener.postMessage("ready", "*")
 </script>
 </body>
 </html>