Implement writing by spawning the CLI as a child process (#400)

After this change, the CLI becomes the only entity actually performing
I/O with the devices, and the GUI is just a wrapper around it.

When you click "Flash", the GUI spawns the CLI with all the appropriate
options, including `--ipc`, which uses an IPC communication channel to
report status back to the parent process.

Signed-off-by: Juan Cruz Viotti <jviottidc@gmail.com>

lib/cli/cli.js

@@ -80,6 +80,14 @@ module.exports = yargs
     return true;
   })
 
+  .check(function(argv) {
+    if (argv.ipc && !process.send) {
+      throw new Error('Can\'t establish an IPC channel with the parent process');
+    }
+
+    return true;
+  })
+
   .options({
     help: {
       describe: 'show help',
@@ -107,6 +115,11 @@ module.exports = yargs
       boolean: true,
       alias: 'r'
     },
+    ipc: {
+      describe: 'communicate through a fork IPC channel',
+      boolean: true,
+      alias: 'i'
+    },
     yes: {
       describe: 'confirm non-interactively',
       boolean: true,
@@ -132,7 +145,11 @@ module.exports = yargs
     // like *.exe and *.cmd in Windows systems.
     const executable = path.basename(argv[0], path.extname(argv[0])).toLowerCase();
 
-    if (executable === 'node' || executable === 'electron') {
+    if (_.includes([
+      'node',
+      'electron',
+      'electron helper'
+    ], executable)) {
 
       // In this case, the second argument (e.g: index 1)
       // equals `lib/cli/etcher.js`, so the real arguments

lib/cli/etcher.js

@@ -42,7 +42,7 @@ form.run([
     // If `options.yes` is `false`, pass `undefined`,
     // otherwise the question will not be asked because
     // `false` is a defined value.
-    yes: options.robot || options.yes || undefined
+    yes: options.robot || options.ipc || options.yes || undefined
 
   }
 }).then(function(answers) {
@@ -70,6 +70,16 @@ form.run([
         state.eta + 's',
         Math.floor(state.speed)
       ].join(' '));
+    } else if (options.ipc) {
+      process.send({
+        command: 'progress',
+        data: {
+          type: state.type,
+          percentage: Math.floor(state.percentage),
+          eta: state.eta,
+          speed: Math.floor(state.speed)
+        }
+      });
     } else {
       progressBars[state.type].update(state);
     }
@@ -79,6 +89,13 @@ form.run([
 
   if (options.robot) {
     console.log(`done ${success}`);
+  } else if (options.ipc) {
+    process.send({
+      command: 'done',
+      data: {
+        success: success
+      }
+    });
   } else {
     if (success) {
       console.log('Your flash is complete!');

lib/gui/modules/analytics.js

@@ -60,6 +60,13 @@ analytics.config(function($mixpanelProvider) {
 // http://docs.trackjs.com/tracker/framework-integrations
 
 analytics.run(function($window) {
+
+  // Don't configure TrackJS when
+  // running inside the test suite
+  if (window.mocha) {
+    return;
+  }
+
   $window.trackJs.configure({
     userId: username.sync(),
     version: packageJSON.version

lib/gui/modules/image-writer.js

@@ -21,21 +21,20 @@
  */
 
 const angular = require('angular');
+const path = require('path');
+const isRunningInAsar = require('electron-is-running-in-asar');
 const electron = require('electron');
-
-if (window.mocha) {
-  var writer = electron.remote.require(require('path').join(__dirname, '..', '..', 'src', 'writer'));
-} else {
-  var writer = electron.remote.require('./src/writer');
-}
+const childProcess = require('child_process');
+const EXIT_CODES = require('../../src/exit-codes');
 
 const MODULE_NAME = 'Etcher.image-writer';
 const imageWriter = angular.module(MODULE_NAME, [
   require('../models/settings'),
+  require('../modules/analytics'),
   require('../utils/notifier/notifier')
 ]);
 
-imageWriter.service('ImageWriterService', function($q, $timeout, SettingsModel, NotifierService) {
+imageWriter.service('ImageWriterService', function($q, $timeout, SettingsModel, NotifierService, AnalyticsService) {
   let self = this;
   let flashing = false;
 
@@ -107,6 +106,7 @@ imageWriter.service('ImageWriterService', function($q, $timeout, SettingsModel,
    * @param {Object} drive - drive
    * @param {Function} onProgress - in progress callback (state)
    *
+   * @fulfil {Boolean} - whether the operation succeeded
    * @returns {Promise}
    *
    * @example
@@ -117,7 +117,73 @@ imageWriter.service('ImageWriterService', function($q, $timeout, SettingsModel,
    * });
    */
   this.performWrite = function(image, drive, onProgress) {
-    return $q.when(writer.writeImage(image, drive, SettingsModel.data, onProgress));
+    const argv = [ image ];
+    argv.push('--drive', drive.device);
+
+    // Make use of `child_process.fork()` facility to send
+    // messages to the parent through an IPC channel.
+    // This allows us to receive the progress state by
+    // listening to the `message` event of the
+    // `ChildProcess` object.
+    argv.push('--ipc');
+
+    // Explicitly set the boolen flag in positive
+    // or negative way in order to be on the safe
+    // side in case the Etcher CLI changes the
+    // default value of these options.
+
+    if (SettingsModel.data.unmountOnSuccess) {
+      argv.push('--unmount');
+    } else {
+      argv.push('--no-unmount');
+    }
+
+    if (SettingsModel.data.validateWriteOnSuccess) {
+      argv.push('--check');
+    } else {
+      argv.push('--no-check');
+    }
+
+    return $q(function(resolve, reject) {
+
+      let executable;
+
+      if (isRunningInAsar()) {
+        executable = path.join(process.resourcesPath, 'app.asar');
+      } else {
+        executable = electron.remote.process.argv[1];
+      }
+
+      AnalyticsService.log(`Forking: ${executable} ${argv.join(' ')}`);
+      const child = childProcess.fork(executable, argv, {
+
+        // Pipe stdout/stderr to the parent
+        // We're not using it directly but its
+        // handy for debugging reasons.
+        silent: true
+
+      });
+
+      child.on('message', function(message) {
+        if (message.command === 'progress') {
+          return onProgress(message.data);
+        }
+      });
+
+      child.on('error', reject);
+
+      child.on('close', function(code) {
+        if (code === EXIT_CODES.SUCCESS) {
+          return resolve(true);
+        }
+
+        if (code === EXIT_CODES.VALIDATION_ERROR) {
+          return resolve(false);
+        }
+
+        return reject(new Error(`Child process exitted with error code: ${code}`));
+      });
+    });
   };
 
   /**
@@ -154,7 +220,7 @@ imageWriter.service('ImageWriterService', function($q, $timeout, SettingsModel,
 
         self.state = {
           type: state.type,
-          progress: Math.floor(state.percentage),
+          progress: state.percentage,
 
           // Transform bytes to megabytes preserving only two decimal places
           speed: Math.floor(state.speed / 1e+6 * 100) / 100 || 0

lib/start.js

@@ -22,7 +22,11 @@
 // *won't* attempt to load the `app.asar` application by default, therefore
 // if passing `ELECTRON_RUN_AS_NODE`, you have to pass the path to the asar
 // or the entry point file (this file) manually as an argument.
-if (process.env.ELECTRON_RUN_AS_NODE) {
+//
+// We also consider `ATOM_SHELL_INTERNAL_RUN_AS_NODE`, which is basically
+// an older equivalent of `ELECTRON_RUN_AS_NODE` that still gets set when
+// using `child_process.fork()`.
+if (process.env.ELECTRON_RUN_AS_NODE || process.env.ATOM_SHELL_INTERNAL_RUN_AS_NODE) {
   require('./cli/etcher');
 
 } else {

package.json

@@ -54,6 +54,7 @@
     "bootstrap-sass": "^3.3.5",
     "chalk": "^1.1.3",
     "drivelist": "^3.0.0",
+    "electron-is-running-in-asar": "^1.0.0",
     "etcher-image-stream": "^1.2.0",
     "etcher-image-write": "^4.0.2",
     "flexboxgrid": "^6.3.0",