make command line args available to render process

src/main/argv.js

@@ -0,0 +1,23 @@
+import minimist from 'minimist';
+
+// inspired by yargs' process-argv
+export const isElectronApp = () => !!process.versions.electron;
+export const isElectronBundledApp = () => isElectronApp() && !process.defaultApp;
+
+export const parseAndTrimArgs = argv => {
+    // bundled Electron app: ignore 1 from "my-app arg1 arg2"
+    // unbundled Electron app: ignore 2 from "electron main/index.js arg1 arg2"
+    // node.js app: ignore 2 from "node src/index.js arg1 arg2"
+    const ignoreCount = isElectronBundledApp() ? 1 : 2;
+
+    const parsed = minimist(argv);
+
+    // ignore arguments AFTER parsing to handle cases like "electron --inspect=42 my.js arg1 arg2"
+    parsed._ = parsed._.slice(ignoreCount);
+
+    return parsed;
+};
+
+const argv = parseAndTrimArgs(process.argv);
+
+export default argv;

src/main/index.js

@@ -3,6 +3,7 @@ import fs from 'fs-extra';
 import path from 'path';
 import {URL} from 'url';
 
+import argv from './argv';
 import {getFilterForExtension} from './FileFilters';
 import telemetry from './ScratchDesktopTelemetry';
 import MacOSMenu from './MacOSMenu';
@@ -373,3 +374,5 @@ app.on('ready', () => {
 ipcMain.on('open-about-window', () => {
     _windows.about.show();
 });
+
+ipcMain.handle('get-argv', () => argv);

src/renderer/app.jsx

@@ -6,6 +6,7 @@ import {compose} from 'redux';
 import GUI, {AppStateHOC} from 'scratch-gui';
 
 import ElectronStorageHelper from '../common/ElectronStorageHelper';
+import log from '../common/log';
 
 import styles from './app.css';
 
@@ -99,4 +100,13 @@ const WrappedGui = compose(
     AppStateHOC
 )(GUI);
 
+ipcRenderer.invoke('get-argv').then(
+    argv => {
+        log.log(`argv._ = ${argv._}`);
+    },
+    err => {
+        log.warn('Failed to retrieve argv', err);
+    }
+);
+
 ReactDOM.render(<WrappedGui />, appTarget);