feature: Installing dependencies with yarn

src/commands/create.js

@@ -6,6 +6,7 @@ import ora from 'ora';
 import promisify from 'es6-promisify';
 import spawn from 'cross-spawn-promise';
 import path from 'path';
+import install from '../lib/install-dependencies';
 import which from 'which';
 
 const TEMPLATES = {
@@ -90,7 +91,7 @@ export default asyncCommand({
 
 		spinner.text = 'Initializing project';
 
-		await npm(target, ['init', '-y']);
+		await spawn('npm', ['init', '-y'], { cwd: target, stdio: 'ignore' });
 
 		let pkg = JSON.parse(await fs.readFile(path.resolve(target, 'package.json')));
 
@@ -119,8 +120,7 @@ export default asyncCommand({
 		if (argv.install) {
 			spinner.text = 'Installing dev dependencies';
 
-			await npm(target, [
-				'install', '--save-dev',
+		await install(target, [
 				'preact-cli',
 				'if-env',
 				'eslint',
@@ -137,12 +137,11 @@ export default asyncCommand({
 					'less',
 					'less-loader'
 				] : [])
-			].filter(Boolean));
+		], 'dev');
 
 			spinner.text = 'Installing dependencies';
 
-			await npm(target, [
-				'install', '--save',
+		await install(target, [
 				'preact',
 				'preact-compat',
 				'preact-router'

src/lib/npm-install-loader.js → src/lib/dependency-install-loader.js

@@ -1,6 +1,7 @@
 import loaderUtils from 'loader-utils';
 import fs from 'fs';
-import spawn from 'cross-spawn-promise';
+import path from 'path';
+import install from './install-dependencies';
 
 /**
  * This is a pass-through loader that runs `npm install --save` for the specified dependencies when invoked.
@@ -30,19 +31,15 @@ const CACHE = {};
 
 function isInstalled(dep) {
 	return CACHE[dep] || (CACHE[dep] = new Promise( resolve => {
-		fs.stat(resolve('node_modules', dep), err => {
+		fs.stat(path.resolve('node_modules', dep), err => {
 			resolve(!err);
 		});
 	}));
 }
 
 function installDeps(deps, save) {
 	process.stdout.write(`\nInstalling ${deps.join(' ')}..`);
-	return spawn('npm', [
-		'install', save && (save==='dev' ? '--save-dev' : '--save'),
-		'--prefix', process.cwd(),
-		...deps
-	].filter(Boolean)).then( () => {
+	return install(process.cwd(), deps, save).then(() => {
 		process.stdout.write(` ..${deps.length} installed.\n`);
 	});
 }

src/lib/install-dependencies.js

@@ -0,0 +1,21 @@
+import spawn from 'cross-spawn-promise';
+import { commandExists } from './shell';
+
+const install = async (cwd, packages, env) => {
+	let isDev = env === 'dev' ? true : false;
+	let isYarnAvailable = await commandExists('yarn');
+	let toInstall = packages.filter(Boolean);
+
+	if (isYarnAvailable) {
+		let args = ['add'];
+		if (isDev) {
+			args.push('-D');
+		}
+
+		return await spawn('yarn', [...args, ...toInstall], { cwd, stdio: 'ignore' });
+	}
+
+	await spawn('npm', ['install', isDev ? '--save-dev' : '--save', ...toInstall], { cwd, stdio: 'ignore' });
+};
+
+export default install;

src/lib/run-webpack.js

@@ -58,7 +58,7 @@ export function showStats(stats) {
 	return stats;
 }
 
-export function writeJsonStats(stats) {
+export async function writeJsonStats(stats) {
 	const outputPath = resolve(process.cwd(), 'stats.json');
 	const jsonStats = stats.toJson({
 		json: true,
@@ -69,13 +69,12 @@ export function writeJsonStats(stats) {
 	jsonStats.modules.forEach(normalizeModule);
 	jsonStats.chunks.forEach(c => c.modules.forEach(normalizeModule));
 
-	return fs.writeFile(outputPath, JSON.stringify(jsonStats))
-		.then(() => {
-			process.stdout.write('\nWebpack output stats generated.\n\n');
-			process.stdout.write('You can upload your stats.json to:\n');
-			process.stdout.write('- https://chrisbateman.github.io/webpack-visualizer/\n');
-			process.stdout.write('- https://webpack.github.io/analyse/\n');
-		});
+	await fs.writeFile(outputPath, JSON.stringify(jsonStats));
+
+	process.stdout.write('\nWebpack output stats generated.\n\n');
+	process.stdout.write('You can upload your stats.json to:\n');
+	process.stdout.write('- https://chrisbateman.github.io/webpack-visualizer/\n');
+	process.stdout.write('- https://webpack.github.io/analyse/\n');
 }
 
 const normalizeModule = m => {

src/lib/shell.js

@@ -0,0 +1,13 @@
+import promisify from 'es6-promisify';
+import which from 'which';
+
+const commandExists = async cmd => {
+	try {
+		await promisify(which)(cmd);
+		return true;
+	} catch (e){
+		return false;
+	}
+};
+
+export { commandExists };

src/lib/webpack-config.js

@@ -165,7 +165,7 @@ export default env => {
 						test: /\.less$/,
 						use: [
 							{
-								loader: resolve(__dirname, './npm-install-loader'),
+								loader: resolve(__dirname, './dependency-install-loader'),
 								options: {
 									modules: ['less', 'less-loader'],
 									save: true
@@ -182,7 +182,7 @@ export default env => {
 						test: /\.s[ac]ss$/,
 						use: [
 							{
-								loader: resolve(__dirname, './npm-install-loader'),
+								loader: resolve(__dirname, './dependency-install-loader'),
 								options: {
 									modules: ['node-sass', 'sass-loader'],
 									save: true