feature: yarn install (through a flag)

src/commands/create.js

@@ -9,6 +9,7 @@ import promisify from 'es6-promisify';
 import spawn from 'cross-spawn-promise';
 import path from 'path';
 import which from 'which';
+import { install, initialize, pkgScripts } from './../lib/setup';
 
 const TEMPLATES = {
 	full: 'examples/full',
@@ -44,6 +45,11 @@ export default asyncCommand({
 			],
 			default: 'full'
 		},
+		yarn: {
+			description: "Use 'yarn' instead of 'npm'",
+			type: 'boolean',
+			default: false
+		},
 		less: {
 			description: 'Pre-install LESS support',
 			type: 'boolean',
@@ -126,18 +132,11 @@ export default asyncCommand({
 
 		spinner.text = 'Initializing project';
 
-		await npm(target, ['init', '-y']);
+		await initialize(argv.yarn, target);
 
 		let pkg = JSON.parse(await fs.readFile(path.resolve(target, 'package.json')));
 
-		pkg.scripts = {
-			...(pkg.scripts || {}),
-			start: 'if-env NODE_ENV=production && npm run -s serve || npm run -s dev',
-			build: 'preact build',
-			serve: 'preact build && preact serve',
-			dev: 'preact watch',
-			test: 'eslint src && preact test'
-		};
+		pkg.scripts = await pkgScripts(argv.yarn, pkg);
 
 		try {
 			await fs.stat(path.resolve(target, 'src'));
@@ -155,8 +154,7 @@ export default asyncCommand({
 		if (argv.install) {
 			spinner.text = 'Installing dev dependencies';
 
-			await npm(target, [
-				'install', '--save-dev',
+			await install(argv.yarn, target, [
 				'preact-cli',
 				'if-env',
 				'eslint',
@@ -179,12 +177,11 @@ export default asyncCommand({
 					'stylus',
 					'stylus-loader'
 				] : [])
-			].filter(Boolean));
+			], 'dev');
 
 			spinner.text = 'Installing dependencies';
 
-			await npm(target, [
-				'install', '--save',
+			await install(argv.yarn, target, [
 				'preact',
 				'preact-compat',
 				'preact-router'
@@ -202,21 +199,19 @@ export default asyncCommand({
 			  \u001b[32mcd ${path.relative(process.cwd(), target)}\u001b[39m
 
 			To start a development live-reload server:
-			  \u001b[32mnpm start\u001b[39m
+			  \u001b[32m${argv.yarn === true ? 'yarnpkg start' : 'npm start'}\u001b[39m
 
 			To create a production build (in ./build):
-			  \u001b[32mnpm run build\u001b[39m
+			  \u001b[32m${argv.yarn === true ? 'yarnpkg build' : 'npm run build'}\u001b[39m
 
 			To start a production HTTP/2 server:
-			  \u001b[32mnpm run serve\u001b[39m
+			  \u001b[32m${argv.yarn === true ? 'yarnpkg serve' : 'npm run serve'}\u001b[39m
 		`) + '\n';
 	}
 });
 
 const trimLeft = (string) => string.trim().replace(/^\t+/gm, '');
 
-const npm = (cwd, args) => spawn('npm', args, { cwd, stdio: 'ignore' });
-
 // Initializes the folder using `git init` and a proper `.gitignore` file
 // if `git` is present in the $PATH.
 async function initializeVersionControl(target) {

src/lib/setup.js

@@ -0,0 +1,55 @@
+import spawn from 'cross-spawn-promise';
+import { commandExists } from './shell';
+
+const initialize = async (yarn, cwd) => {
+	let isYarnAvailable = await commandExists('yarn');
+
+	if (isYarnAvailable && yarn) {
+		return await spawn('yarn', ['init', '-y'], { cwd, stdio: 'ignore' });
+	}
+
+	await spawn('npm', ['init', '-y'], { cwd, stdio: 'ignore' });
+};
+
+const install = async (yarn, cwd, packages, env) => {
+	let isDev = env === 'dev' ? true : false;
+	let isYarnAvailable = await commandExists('yarn');
+	let toInstall = packages.filter(Boolean);
+
+	if (isYarnAvailable && yarn) {
+		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' });
+};
+
+const pkgScripts = async (yarn, pkg) => {
+	let isYarnAvailable = await commandExists('yarn');
+
+	if (isYarnAvailable && yarn) {
+		return {
+			...(pkg.scripts || {}),
+			start: 'if-env NODE_ENV=production && yarnpkg -s serve || yarnpkg -s dev',
+			build: 'preact build',
+			serve: 'preact build && preact serve',
+			dev: 'preact watch',
+			test: 'eslint src && preact test'
+		};
+	}
+
+	return {
+		...(pkg.scripts || {}),
+		start: 'if-env NODE_ENV=production && npm run -s serve || npm run -s dev',
+		build: 'preact build',
+		serve: 'preact build && preact serve',
+		dev: 'preact watch',
+		test: 'eslint src && preact test'
+	};
+};
+
+export { install, initialize, pkgScripts };

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

@@ -1,14 +1,15 @@
 import loaderUtils from 'loader-utils';
 import fs from 'fs';
-import spawn from 'cross-spawn-promise';
+import path from 'path';
+import { install } from './../setup';
 
 /**
  * This is a pass-through loader that runs `npm install --save` for the specified dependencies when invoked.
  * Chain it before loaders to conditionally install them on first use.
  * Quickly checks if any modules are alread installed and skips them.
  * @param {object} options
- * @param {boolean|string} [options.save=false]		If `true`, runs `npm i --save`. If `"dev"`, runs `npm i --save-dev`.
- * @param {Array<String>|String} modules			A list of modules to install.
+ * @param {boolean|string} [options.save=false]  If `true`, runs `npm i --save`. If `"dev"`, runs `npm i --save-dev`.
+ * @param {Array<String>|String} modules         A list of modules to install.
  *
  * @example // Install and use less-loader and less when encountering `.less` files:
  *
@@ -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 ${deps.join(' ')}..`);
-	return spawn('npm', [
-		'install', save && (save==='dev' ? '--save-dev' : '--save'),
-		'--prefix', process.cwd(),
-		...deps
-	].filter(Boolean)).then( () => {
+	return install(false, process.cwd(), deps, save).then( () => {
 		process.stdout.write(` ..${deps.length} installed.\n`);
 	});
 }

src/lib/webpack/webpack-base-config.js

@@ -109,7 +109,7 @@ export default (env) => {
 						test: /\.less$/,
 						use: [
 							{
-								loader: resolve(__dirname, './npm-install-loader'),
+								loader: resolve(__dirname, './dependency-install-loader'),
 								options: {
 									modules: ['less', 'less-loader'],
 									save: true
@@ -126,7 +126,7 @@ export default (env) => {
 						test: /\.s[ac]ss$/,
 						use: [
 							{
-								loader: resolve(__dirname, './npm-install-loader'),
+								loader: resolve(__dirname, './dependency-install-loader'),
 								options: {
 									modules: ['node-sass', 'sass-loader'],
 									save: true
@@ -143,7 +143,7 @@ export default (env) => {
 						test: /\.styl$/,
 						use: [
 							{
-								loader: resolve(__dirname, './npm-install-loader'),
+								loader: resolve(__dirname, './dependency-install-loader'),
 								options: {
 									modules: ['stylus', 'stylus-loader'],
 									save: true