feat: Support running cypress as node process (cypress-io#16505)

This change checks if the environment variable
ELECTRON_RUN_AS_NODE is set. If set to true, the cypress
process is started as a normal Node.js process rather than an
electron process.

Consequently, the process does not require a display server to
run so starting a display server is skipped.

cli/lib/exec/spawn.js

@@ -141,9 +141,22 @@ module.exports = {
           stdioOptions.env.DISPLAY = process.env.DISPLAY
         }
 
+        if (process.env.ELECTRON_RUN_AS_NODE === 'true') {
+          debug('passing ELECTRON_RUN_AS_NODE=true')
+          stdioOptions.env.ELECTRON_RUN_AS_NODE = 'true'
+
+          // Replace electron specific args with path to js entry point.
+          electronArgs.splice(
+            0,
+            // Electron's command line switches come before the "--" delimiter.
+            electronArgs.indexOf('--') + 1,
+            // Replace package path with entry point path
+            path.join(state.getBinaryPkgPath(path.dirname(executable)), '..', 'index.js'),
+          )
+        }
+
         debug('spawning Cypress with executable: %s', executable)
         debug('spawn args %o %o', electronArgs, _.omit(stdioOptions, 'env'))
-
         const child = cp.spawn(executable, electronArgs, stdioOptions)
 
         function resolveOn (event) {

cli/lib/exec/xvfb.js

@@ -58,6 +58,10 @@ module.exports = {
   },
 
   isNeeded () {
+    if (process.env.ELECTRON_RUN_AS_NODE === 'true') {
+      return false // xvfb required for electron processes only.
+    }
+
     if (os.platform() !== 'linux') {
       return false
     }

packages/server/lib/ipc/ipc.js

@@ -1,9 +1,15 @@
-const {
-  contextBridge,
-  ipcRenderer,
-} = require('electron')
+const debug = require('debug')('cypress:server:ipc')
 
-contextBridge.exposeInMainWorld('ipc', {
-  on: (...args) => ipcRenderer.on(...args),
-  send: (...args) => ipcRenderer.send(...args),
-})
+try {
+  const {
+    contextBridge,
+    ipcRenderer,
+  } = require('electron')
+
+  contextBridge.exposeInMainWorld('ipc', {
+    on: (...args) => ipcRenderer.on(...args),
+    send: (...args) => ipcRenderer.send(...args),
+  })
+} catch {
+  debug('running as a node process, not an electron process')
+}

packages/server/lib/modes/run.js

@@ -1,6 +1,5 @@
 /* eslint-disable no-console, @cypress/dev/arrow-body-multiline-braces  */
 const _ = require('lodash')
-const { app } = require('electron')
 const la = require('lazy-ass')
 const pkg = require('@packages/root')
 const path = require('path')
@@ -1652,14 +1651,20 @@ module.exports = {
   },
 
   async run (options) {
-    // electron >= 5.0.0 will exit the app if all browserwindows are closed,
-    // this is obviously undesirable in run mode
-    // https://github.com/cypress-io/cypress/pull/4720#issuecomment-514316695
-    app.on('window-all-closed', () => {
-      debug('all BrowserWindows closed, not exiting')
-    })
+    try {
+      const { app } = require('electron')
+
+      // electron >= 5.0.0 will exit the app if all browserwindows are closed,
+      // this is obviously undesirable in run mode
+      // https://github.com/cypress-io/cypress/pull/4720#issuecomment-514316695
+      app.on('window-all-closed', () => {
+        debug('all BrowserWindows closed, not exiting')
+      })
 
-    await app.whenReady()
+      await app.whenReady()
+    } catch {
+      debug('running as a node process, not an electron process')
+    }
 
     return this.ready(options)
   },

packages/server/package.json

@@ -187,7 +187,7 @@
     "webpack": "4.43.0",
     "ws": "5.2.3",
     "xvfb": "cypress-io/node-xvfb#22e3783c31d81ebe64d8c0df491ea00cdc74726a",
-    "xvfb-maybe": "0.2.1"
+    "xvfb-maybe": "^0.2.1"
   },
   "files": [
     "config",

packages/server/test/e2e/5_headless_spec.ts

@@ -4,6 +4,30 @@ import Fixtures from '../support/helpers/fixtures'
 describe('e2e headless', function () {
   e2e.setup()
 
+  describe('ELECTRON_RUN_AS_NODE', () => {
+    beforeEach(function () {
+      process.env.ELECTRON_RUN_AS_NODE = 'true'
+    })
+
+    // cypress run --headless
+    e2e.it('tests in headless mode pass', {
+      spec: 'headless_spec.js',
+      config: {
+        env: {
+          'CI': process.env.CI,
+          'EXPECT_HEADLESS': '1',
+        },
+      },
+      headed: false,
+      snapshot: true,
+      browser: 'chrome',
+    })
+
+    after(function () {
+      process.env.ELECTRON_RUN_AS_NODE = ''
+    })
+  })
+
   // cypress run --headless
   e2e.it('tests in headless mode pass', {
     spec: 'headless_spec.js',