Allow ASAR to work with child_process.spawn()

[sindresorhus]

There are Node APIs that can execute binaries like child_process.exec, child_process.spawn and child_process.execFile, but only execFile is supported to execute binaries inside asar archive.

This is because exec and spawn accept command instead of file as input, and commands are executed under shell.

• https://github.com/electron/electron/blob/master/docs/tutorial/application-packaging.md#executing-binaries-inside-asar-archive

This is not entirely correct. .spawn() executes the binary directly by default, just as .execFile() does. .execFile() actually uses .spawn() underneath. .spawn() only runs the input in a shell if the shell option is set.

Not supporting .spawn() means a lot of apps are not able to use ASAR as they need the more flexible .spawn() method. For example, I need the .spawn() method so I can stream the output of ffmpeg while it's running. .execFile() only buffers and reports at the end.

Would also make sense to support .spawnSync() for completeness.

---

See #3512 for previous discussion.

[seanzer]

I get the caveats to supporting spawn, but there are valid use cases that would not be affected by the ASAR. I want to spawn an executable which is not packed in the asar, and to be able to configure the environment. I think it's worth documenting that inspecting the asar from another processes may fail, but at least supporting spawn would enable some of us to be able to use asar.

[sindresorhus]

For anyone looking for a temporary workaround, check out: https://github.com/sindresorhus/electron-util#fixpathforasarunpackpath

[nuthinking]

@sindresorhus how to make the workaround work with electron-packager?

[midevnull]

@sindresorhus how can I use your fix with with modules like imagemin-optipng? Is there another way than manualy chage the module and prevent overwrites by the original module.

The weird thing is that imagemin-jpegtran (uses spawn as well) works but imagemin-optipng doesnt.

[Richard-Choooou]

@sindresorhus Aha, I got this problem too.

[Richard-Choooou]

@midevnull you can try to set "asar" to false in package.json, like this

"build": {
    "asar": false
  },

[michaeljpeake]

@midevnull you can try to set "asar" to false in package.json, like this

"build": {
    "asar": false
  },

Or you can use asarUnpack and specify what you want to leave out. Personally, I'm not seeing many benefits from using asar. Willing to be educated in what they are though.

[ayizhi]

pm2 use Client Object in pm2/lib/Client.js to start a Daemon

Client.prototype.launchDaemon = function(opts, cb) {
  ...
  var child = require('child_process').spawn(interpreter, node_args, {
    detached   : true,
    cwd        : that.conf.cwd || process.cwd(),
    env        : util._extend({
      'SILENT'      : that.conf.DEBUG ? !that.conf.DEBUG : true,
      'PM2_HOME'   : that.pm2_home
    }, process.env),
    stdio      : ['ipc', out, err]
  });

};

In theory，this method can be hacked

require('pm2').Client.__proto__.launchDaemon = function (opts, cb) {
  ...
  var ClientJS = path.resolve(path.dirname(module.filename), 'Daemon.js');
  var child = require('child_process').fork(ClientJS, node_args, {
    detached   : true,
    cwd        : that.conf.cwd || process.cwd(),
    env        : util._extend({
      'SILENT'      : that.conf.DEBUG ? !that.conf.DEBUG : true,
      'PM2_HOME'   : that.pm2_home
    }, process.env),
    stdio      : ['ipc', out, err]
  })
}

by this way, we are able to replace launchDaemon by ourself's, in which we can use fork to start Daemon
and if we start Daemon by child_process.fork, asar can be set to "true"

[agentcooper]

To make my app work with ASAR, I am calling this helper function before the code that uses child_process.spawn:

import * as child_process from "child_process"

/**
 * To be used with 'asarUnpack' option in electron-builder.
 */
export function patchSpawnForASAR(): void {
    const originalSpawn = child_process.spawn

    const asarSpawn = (command: string, args?: string[], options?: object) => {
        return originalSpawn(
            command,
            args ? args.map((arg) => arg.replace("app.asar", "app.asar.unpacked")) : undefined,
            options
        )
    }

    ;(child_process as any).spawn = asarSpawn
}

(paste into https://www.typescriptlang.org/play to get JavaScript version)

[kostas-jonauskas]

You can include your executables as ExtraResources so they won't get packaged into ASAR archive.