feat: UtilityProcess API

BUILD.gn

@@ -210,13 +210,23 @@ webpack_build("electron_isolated_renderer_bundle") {
   out_file = "$target_gen_dir/js2c/isolated_bundle.js"
 }
 
+webpack_build("electron_utility_bundle") {
+  deps = [ ":build_electron_definitions" ]
+
+  inputs = auto_filenames.utility_bundle_deps
+
+  config_file = "//electron/build/webpack/webpack.config.utility.js"
+  out_file = "$target_gen_dir/js2c/utility_init.js"
+}
+
 action("electron_js2c") {
   deps = [
     ":electron_asar_bundle",
     ":electron_browser_bundle",
     ":electron_isolated_renderer_bundle",
     ":electron_renderer_bundle",
     ":electron_sandboxed_renderer_bundle",
+    ":electron_utility_bundle",
     ":electron_worker_bundle",
   ]
 
@@ -226,6 +236,7 @@ action("electron_js2c") {
     "$target_gen_dir/js2c/isolated_bundle.js",
     "$target_gen_dir/js2c/renderer_init.js",
     "$target_gen_dir/js2c/sandbox_bundle.js",
+    "$target_gen_dir/js2c/utility_init.js",
     "$target_gen_dir/js2c/worker_init.js",
   ]
 
@@ -406,6 +417,7 @@ source_set("electron_lib") {
     "chromium_src:chrome",
     "chromium_src:chrome_spellchecker",
     "shell/common/api:mojo",
+    "shell/services/node/public/mojom",
     "//base:base_static",
     "//base/allocator:buildflags",
     "//chrome:strings",

build/webpack/webpack.config.utility.js

@@ -0,0 +1,4 @@
+module.exports = require('./webpack.config.base')({
+  target: 'utility',
+  alwaysHasNode: true
+});

docs/api/parent-port.md

@@ -0,0 +1,46 @@
+# parentPort
+
+> Interface for communication with parent process.
+
+Process: [Utility](../glossary.md#utility-process)
+
+`parentPort` is an [EventEmitter][event-emitter].
+_This object is not exported from the `'electron'` module. It is only available as a property of the process object in the Electron API._
+
+```js
+// Main process
+const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
+child.postMessage({ message: 'hello' })
+child.on('message', (data) => {
+  console.log(data) // hello world!
+})
+
+// Child process
+process.parentPort.on('message', (e) => {
+  process.parentPort.postMessage(`${e.data} world!`)
+})
+```
+
+## Events
+
+The `parentPort` object emits the following events:
+
+### Event: 'message'
+
+Returns:
+
+* `messageEvent` Object
+  * `data` any
+  * `ports` MessagePortMain[]
+
+Emitted when the process receives a message. Messages received on
+this port will be queued up until a handler is registered for this
+event.
+
+## Methods
+
+### `parentPort.postMessage(message)`
+
+* `message` any
+
+Sends a message from the process to its parent.

docs/api/process.md

@@ -113,6 +113,7 @@ A `string` representing the current process's type, can be:
 * `browser` - The main process
 * `renderer` - A renderer process
 * `worker` - In a web worker
+* `utility` - In a node process launched as a service
 
 ### `process.versions.chrome` _Readonly_
 
@@ -134,6 +135,11 @@ Each frame has its own JavaScript context. When contextIsolation is enabled, the
 world also has a separate JavaScript context.
 This property is only available in the renderer process.
 
+### `process.parentPort`
+
+A [`Electron.ParentPort`](parent-port.md) property if this is a [`UtilityProcess`](utility-process.md)
+(or `null` otherwise) allowing communication with the parent process.
+
 ## Methods
 
 The `process` object has the following methods:

docs/api/utility-process.md

@@ -0,0 +1,136 @@
+# utilityProcess
+
+`utilityProcess` creates a child process with
+Node.js and Message ports enabled. It provides the equivalent of [`child_process.fork`][] API from Node.js
+but instead uses [Services API][] from Chromium to launch the child process.
+
+Process: [Main](../glossary.md#main-process)<br />
+
+## Methods
+
+### `utilityProcess.fork(modulePath[, args][, options])`
+
+* `modulePath` string - Path to the script that should run as entrypoint in the child process.
+* `args` string[] (optional) - List of string arguments that will be available as `process.argv`
+  in the child process.
+* `options` Object (optional)
+  * `env` Object (optional) - Environment key-value pairs. Default is `process.env`.
+  * `execArgv` string[] (optional) - List of string arguments passed to the executable.
+  * `cwd` string (optional) - Current working directory of the child process.
+  * `stdio` (string[] | string) (optional) - Allows configuring the mode for `stdout` and `stderr`
+    of the child process. Default is `inherit`.
+    String value can be one of `pipe`, `ignore`, `inherit`, for more details on these values you can refer to
+    [stdio][] documentation from Node.js. Currently this option only supports configuring `stdout` and
+    `stderr` to either `pipe`, `inherit` or `ignore`. Configuring `stdin` is not supported; `stdin` will
+    always be ignored.
+    For example, the supported values will be processed as following:
+    * `pipe`: equivalent to ['ignore', 'pipe', 'pipe'] (the default)
+    * `ignore`: equivalent to 'ignore', 'ignore', 'ignore']
+    * `inherit`: equivalent to ['ignore', 'inherit', 'inherit']
+  * `serviceName` string (optional) - Name of the process that will appear in `name` property of
+    [`child-process-gone` event of `app`](app.md#event-child-process-gone).
+    Default is `node.mojom.NodeService`.
+  * `allowLoadingUnsignedLibraries` boolean (optional) _macOS_ - With this flag, the utility process will be
+    launched via the `Electron Helper (Plugin).app` helper executable on macOS, which can be
+    codesigned with `com.apple.security.cs.disable-library-validation` and
+    `com.apple.security.cs.allow-unsigned-executable-memory` entitlements. This will allow the utility process
+    to load unsigned libraries. Unless you specifically need this capability, it is best to leave this disabled.
+    Default is `false`.
+
+Returns [`UtilityProcess`](utility-process.md#class-utilityprocess)
+
+## Class: UtilityProcess
+
+> Instances of the `UtilityProcess` represent the Chromium spawned child process
+> with Node.js integration.
+
+`UtilityProcess` is an [EventEmitter][event-emitter].
+
+### Instance Methods
+
+#### `child.postMessage(message, [transfer])`
+
+* `message` any
+* `transfer` MessagePortMain[] (optional)
+
+Send a message to the child process, optionally transferring ownership of
+zero or more [`MessagePortMain`][] objects.
+
+For example:
+
+```js
+// Main process
+const { port1, port2 } = new MessageChannelMain()
+const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
+child.postMessage({ message: 'hello' }, [port1])
+
+// Child process
+process.parentPort.once('message', (e) => {
+  const [port] = e.ports
+  // ...
+})
+```
+
+#### `child.kill()`
+
+Returns `boolean`
+
+Terminates the process gracefully. On POSIX, it uses SIGTERM
+but will ensure the process is reaped on exit. This function returns
+true if the kill is successful, and false otherwise.
+
+### Instance Properties
+
+#### `child.pid`
+
+A `Integer | undefined` representing the process identifier (PID) of the child process.
+If the child process fails to spawn due to errors, then the value is `undefined`. When
+the child process exits, then the value is `undefined` after the `exit` event is emitted.
+
+#### `child.stdout`
+
+A `NodeJS.ReadableStream | null` that represents the child process's stdout.
+If the child was spawned with options.stdio[1] set to anything other than 'pipe', then this will be `null`.
+When the child process exits, then the value is `null` after the `exit` event is emitted.
+
+```js
+// Main process
+const { port1, port2 } = new MessageChannelMain()
+const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
+child.stdout.on('data', (data) => {
+  console.log(`Received chunk ${data}`)
+})
+```
+
+#### `child.stderr`
+
+A `NodeJS.ReadableStream | null` that represents the child process's stderr.
+If the child was spawned with options.stdio[2] set to anything other than 'pipe', then this will be `null`.
+When the child process exits, then the value is `null` after the `exit` event is emitted.
+
+### Instance Events
+
+#### Event: 'spawn'
+
+Emitted once the child process has spawned successfully.
+
+#### Event: 'exit'
+
+Returns:
+
+* `code` number - Contains the exit code for
+the process obtained from waitpid on posix, or GetExitCodeProcess on windows.
+
+Emitted after the child process ends.
+
+#### Event: 'message'
+
+Returns:
+
+* `message` any
+
+Emitted when the child process sends a message using [`process.parentPort.postMessage()`](process.md#processparentport).
+
+[`child_process.fork`]: https://nodejs.org/dist/latest-v16.x/docs/api/child_process.html#child_processforkmodulepath-args-options
+[Services API]: https://chromium.googlesource.com/chromium/src/+/master/docs/mojo_and_services.md
+[stdio]: https://nodejs.org/dist/latest/docs/api/child_process.html#optionsstdio

docs/glossary.md

@@ -194,6 +194,15 @@ overly prescriptive about how it should be used. Userland enables users to
 create and share tools that provide additional functionality on top of what is
 available in "core".
 
+### utility process
+
+The utility process is a child of the main process that allows running any
+untrusted services that cannot be run in the main process. Chromium uses this
+process to perform network I/O, audio/video processing, device inputs etc.
+In Electron, you can create this process using [UtilityProcess][] API.
+
+See also: [process](#process), [main process](#main-process)
+
 ### V8
 
 V8 is Google's open source JavaScript engine. It is written in C++ and is
@@ -231,4 +240,5 @@ embedded content.
 [renderer]: #renderer-process
 [userland]: #userland
 [using native node modules]: tutorial/using-native-node-modules.md
+[UtilityProcess]: api/utility-process.md
 [v8]: #v8

docs/tutorial/process-model.md

@@ -214,8 +214,25 @@ This feature is incredibly useful for two main purposes:
   URL, you can add custom properties onto the renderer's `window` global that can
   be used for desktop-only logic on the web client's side.
 
+## The utility process
+
+Each Electron app can spawn multiple child processes from the main process using
+the [UtilityProcess][] API. The utility process runs in a Node.js environment,
+meaning it has the ability to `require` modules and use all of Node.js APIs.
+The utility process can be used to host for example: untrusted services,
+CPU intensive tasks or crash prone components which would have previously
+been hosted in the main process or process spawned with Node.js [`child_process.fork`][] API.
+The primary difference between the utility process and process spawned by Node.js
+child_process module is that the utility process can establish a communication
+channel with a renderer process using [`MessagePort`][]s. An Electron app can
+always prefer the [UtilityProcess][] API over Node.js [`child_process.fork`][] API when
+there is need to fork a child process from the main process.
+
 [window-mdn]: https://developer.mozilla.org/en-US/docs/Web/API/Window
+[`MessagePort`]: https://developer.mozilla.org/en-US/docs/Web/API/MessagePort
+[`child_process.fork`]: https://nodejs.org/dist/latest-v16.x/docs/api/child_process.html#child_processforkmodulepath-args-options
 [context-isolation]: ./context-isolation.md
 [context-bridge]: ../api/context-bridge.md
 [ipcrenderer]: ../api/ipc-renderer.md
+[UtilityProcess]: ../api/utility-process.md
 [tutorial]: ./tutorial-1-prerequisites.md

filenames.auto.gni

@@ -36,6 +36,7 @@ auto_filenames = {
     "docs/api/net-log.md",
     "docs/api/net.md",
     "docs/api/notification.md",
+    "docs/api/parent-port.md",
     "docs/api/power-monitor.md",
     "docs/api/power-save-blocker.md",
     "docs/api/process.md",
@@ -62,6 +63,7 @@ auto_filenames = {
     "docs/api/touch-bar-spacer.md",
     "docs/api/touch-bar.md",
     "docs/api/tray.md",
+    "docs/api/utility-process.md",
     "docs/api/web-contents.md",
     "docs/api/web-frame-main.md",
     "docs/api/web-frame.md",
@@ -220,6 +222,7 @@ auto_filenames = {
     "lib/browser/api/system-preferences.ts",
     "lib/browser/api/touch-bar.ts",
     "lib/browser/api/tray.ts",
+    "lib/browser/api/utility-process.ts",
     "lib/browser/api/view.ts",
     "lib/browser/api/views/image-view.ts",
     "lib/browser/api/web-contents-view.ts",
@@ -331,4 +334,20 @@ auto_filenames = {
     "typings/internal-ambient.d.ts",
     "typings/internal-electron.d.ts",
   ]
+
+  utility_bundle_deps = [
+    "lib/browser/message-port-main.ts",
+    "lib/common/define-properties.ts",
+    "lib/common/init.ts",
+    "lib/common/reset-search-paths.ts",
+    "lib/utility/api/exports/electron.ts",
+    "lib/utility/api/module-list.ts",
+    "lib/utility/init.ts",
+    "lib/utility/parent-port.ts",
+    "package.json",
+    "tsconfig.electron.json",
+    "tsconfig.json",
+    "typings/internal-ambient.d.ts",
+    "typings/internal-electron.d.ts",
+  ]
 }

filenames.gni

@@ -313,6 +313,8 @@ filenames = {
     "shell/browser/api/electron_api_tray.h",
     "shell/browser/api/electron_api_url_loader.cc",
     "shell/browser/api/electron_api_url_loader.h",
+    "shell/browser/api/electron_api_utility_process.cc",
+    "shell/browser/api/electron_api_utility_process.h",
     "shell/browser/api/electron_api_view.cc",
     "shell/browser/api/electron_api_view.h",
     "shell/browser/api/electron_api_web_contents.cc",
@@ -678,6 +680,10 @@ filenames = {
     "shell/renderer/renderer_client_base.h",
     "shell/renderer/web_worker_observer.cc",
     "shell/renderer/web_worker_observer.h",
+    "shell/services/node/node_service.cc",
+    "shell/services/node/node_service.h",
+    "shell/services/node/parent_port.cc",
+    "shell/services/node/parent_port.h",
     "shell/utility/electron_content_utility_client.cc",
     "shell/utility/electron_content_utility_client.h",
   ]

lib/browser/api/module-list.ts

@@ -31,6 +31,7 @@ export const browserModuleList: ElectronInternal.ModuleEntry[] = [
   { name: 'systemPreferences', loader: () => require('./system-preferences') },
   { name: 'TouchBar', loader: () => require('./touch-bar') },
   { name: 'Tray', loader: () => require('./tray') },
+  { name: 'utilityProcess', loader: () => require('./utility-process') },
   { name: 'View', loader: () => require('./view') },
   { name: 'webContents', loader: () => require('./web-contents') },
   { name: 'WebContentsView', loader: () => require('./web-contents-view') },