electron/lib/sandboxed_renderer/init.ts

import * as events from 'events';
import { IPC_MESSAGES } from '@electron/internal/common/ipc-messages';

import type * as ipcRendererUtilsModule from '@electron/internal/renderer/ipc-renderer-internal-utils';
import type * as ipcRendererInternalModule from '@electron/internal/renderer/ipc-renderer-internal';

declare const binding: {
  get: (name: string) => any;
  process: NodeJS.Process;
  createPreloadScript: (src: string) => Function
};

const { EventEmitter } = events;

process._linkedBinding = binding.get;

const v8Util = process._linkedBinding('electron_common_v8_util');
// Expose Buffer shim as a hidden value. This is used by C++ code to
// deserialize Buffer instances sent from browser process.
v8Util.setHiddenValue(global, 'Buffer', Buffer);
// The process object created by webpack is not an event emitter, fix it so
// the API is more compatible with non-sandboxed renderers.
for (const prop of Object.keys(EventEmitter.prototype) as (keyof typeof process)[]) {
  if (Object.hasOwn(process, prop)) {
    delete process[prop];
  }
}
Object.setPrototypeOf(process, EventEmitter.prototype);

const { ipcRendererInternal } = require('@electron/internal/renderer/ipc-renderer-internal') as typeof ipcRendererInternalModule;
const ipcRendererUtils = require('@electron/internal/renderer/ipc-renderer-internal-utils') as typeof ipcRendererUtilsModule;

const {
  preloadScripts,
  process: processProps
} = ipcRendererUtils.invokeSync<{
  preloadScripts: {
    preloadPath: string;
    preloadSrc: string | null;
    preloadError: null | Error;
  }[];
  process: NodeJS.Process;
}>(IPC_MESSAGES.BROWSER_SANDBOX_LOAD);

const electron = require('electron');

const loadedModules = new Map<string, any>([
  ['electron', electron],
  ['electron/common', electron],
  ['electron/renderer', electron],
  ['events', events],
  ['node:events', events]
]);

const loadableModules = new Map<string, Function>([
  ['timers', () => require('timers')],
  ['node:timers', () => require('timers')],
  ['url', () => require('url')],
  ['node:url', () => require('url')]
]);

// Pass different process object to the preload script.
const preloadProcess: NodeJS.Process = new EventEmitter() as any;

// InvokeEmitProcessEvent in ElectronSandboxedRendererClient will look for this
v8Util.setHiddenValue(global, 'emit-process-event', (event: string) => {
  (process as events.EventEmitter).emit(event);
  (preloadProcess as events.EventEmitter).emit(event);
});

Object.assign(preloadProcess, binding.process);
Object.assign(preloadProcess, processProps);

Object.assign(process, binding.process);
Object.assign(process, processProps);

process.getProcessMemoryInfo = preloadProcess.getProcessMemoryInfo = () => {
  return ipcRendererInternal.invoke<Electron.ProcessMemoryInfo>(IPC_MESSAGES.BROWSER_GET_PROCESS_MEMORY_INFO);
};

Object.defineProperty(preloadProcess, 'noDeprecation', {
  get () {
    return process.noDeprecation;
  },
  set (value) {
    process.noDeprecation = value;
  }
});

// This is the `require` function that will be visible to the preload script
function preloadRequire (module: string) {
  if (loadedModules.has(module)) {
    return loadedModules.get(module);
  }
  if (loadableModules.has(module)) {
    const loadedModule = loadableModules.get(module)!();
    loadedModules.set(module, loadedModule);
    return loadedModule;
  }
  throw new Error(`module not found: ${module}`);
}

// Process command line arguments.
const { hasSwitch } = process._linkedBinding('electron_common_command_line');

// Similar to nodes --expose-internals flag, this exposes _linkedBinding so
// that tests can call it to get access to some test only bindings
if (hasSwitch('unsafely-expose-electron-internals-for-testing')) {
  preloadProcess._linkedBinding = process._linkedBinding;
}

// Common renderer initialization
require('@electron/internal/renderer/common-init');

// Wrap the script into a function executed in global scope. It won't have
// access to the current scope, so we'll expose a few objects as arguments:
//
// - `require`: The `preloadRequire` function
// - `process`: The `preloadProcess` object
// - `Buffer`: Shim of `Buffer` implementation
// - `global`: The window object, which is aliased to `global` by webpack.
function runPreloadScript (preloadSrc: string) {
  const preloadWrapperSrc = `(function(require, process, Buffer, global, setImmediate, clearImmediate, exports, module) {
  ${preloadSrc}
  })`;

  // eval in window scope
  const preloadFn = binding.createPreloadScript(preloadWrapperSrc);
  const { setImmediate, clearImmediate } = require('timers');
  const exports = {};

  preloadFn(preloadRequire, preloadProcess, Buffer, global, setImmediate, clearImmediate, exports, { exports });
}

for (const { preloadPath, preloadSrc, preloadError } of preloadScripts) {
  try {
    if (preloadSrc) {
      runPreloadScript(preloadSrc);
    } else if (preloadError) {
      throw preloadError;
    }
  } catch (error) {
    console.error(`Unable to load preload script: ${preloadPath}`);
    console.error(error);

    ipcRendererInternal.send(IPC_MESSAGES.BROWSER_PRELOAD_ERROR, preloadPath, error);
  }
}