Use yarn when available

Summary:
**Motivation**

`react-native init` takes minutes even on a fast network. Yarn makes it much quicker.

When yarn is not installed on the system:

<img width="440" alt="screenshot 2016-10-31 22 21 19" src="https://cloud.githubusercontent.com/assets/346214/19873897/7bad5662-9fb9-11e6-85fb-ad4879949dad.png">

When yarn is installed:

<img width="441" alt="screenshot 2016-10-31 22 02 20" src="https://cloud.githubusercontent.com/assets/346214/19873898/7baf4c56-9fb9-11e6-96b3-007f93d2438a.png">

Also added the option `react-native init AwesomeApp --npm` as a fallback in case yarn is not stable enough for some people (I saw some Github issues that yarn hangs for example; for me it works great though).

**Test plan**
1. Publish to Sinopia: https://github.com/facebook/react-native/tree/master/react-native-cli
2. `react-native init AwesomeApp`

***Tested the following setups***

- New CLI - uses yarn, new react-native - uses yarn
- Old CLI (1.0.0) - doesn't use yarn, new react-native - uses yarn
-
Closes https://github.com/facebook/react-native/pull/10626

Differential Revision: D4110883

Pulled By: bestander

fbshipit-source-id: 8a3427e2bc9158cf5fadd8ddf5b31e4b50ce6453

local-cli/generator/index.js

@@ -8,11 +8,40 @@
  */
 'use strict';
 
+var execSync = require('child_process').execSync;
 var fs = require('fs');
 var path = require('path');
+var semver = require('semver')
 var utils = require('../generator-utils');
 var yeoman = require('yeoman-generator');
 
+// Use Yarn if available, it's much faster than the npm client.
+// Return the version of yarn installed on the system, null if yarn is not available.
+function getYarnVersionIfAvailable() {
+  let yarnVersion;
+  try {
+    // execSync returns a Buffer -> convert to string
+    if (process.platform.startsWith('win')) {
+      yarnVersion = (execSync('yarn --version').toString() || '').trim();
+    } else {
+      yarnVersion = (execSync('yarn --version 2>/dev/null').toString() || '').trim();
+    }
+  } catch (error) {
+    return null;
+  }
+  // yarn < 0.16 has a 'missing manifest' bug
+  try {
+    if (semver.gte(yarnVersion, '0.16.0')) {
+      return yarnVersion;
+    } else {
+      return null;
+    }
+  } catch (error) {
+    console.error('Cannot parse yarn version: ' + yarnVersion);
+    return null;
+  }
+}
+
 module.exports = yeoman.generators.NamedBase.extend({
   constructor: function() {
     yeoman.generators.NamedBase.apply(this, arguments);
@@ -36,6 +65,12 @@ module.exports = yeoman.generators.NamedBase.extend({
       type: Boolean,
       defaults: false
     });
+    // Temporary option until yarn becomes stable.
+    this.option('npm', {
+      desc: 'Use the npm client, even if yarn is available.',
+      type: Boolean,
+      defaults: false
+    });
 
     // this passes command line arguments down to the composed generators
     var args = {args: arguments[0], options: this.options};
@@ -112,12 +147,24 @@ module.exports = yeoman.generators.NamedBase.extend({
       return;
     }
 
+    const yarnVersion = (!this.options['npm']) && getYarnVersionIfAvailable();
+
+    console.log('Installing React...');
+    if (yarnVersion) {
+      execSync(`yarn add react@${reactVersion}`);
+    } else {
       this.npmInstall(`react@${reactVersion}`, { '--save': true, '--save-exact': true });
+    }
     if (!this.options['skip-jest']) {
+      console.log('Installing Jest...');
+      if (yarnVersion) {
+        execSync(`yarn add jest babel-jest jest-react-native babel-preset-react-native react-test-renderer@${reactVersion} --dev --exact`);
+      } else {
         this.npmInstall(`jest babel-jest babel-preset-react-native react-test-renderer@${reactVersion}`.split(' '), {
           saveDev: true,
           '--save-exact': true
         });
+      }
       fs.writeFileSync(
         path.join(
           this.destinationRoot(),
@@ -125,7 +172,6 @@ module.exports = yeoman.generators.NamedBase.extend({
         ),
         '{\n"presets": ["react-native"]\n}'
       );
-
       this.fs.copy(
         this.templatePath('__tests__'),
         this.destinationPath('__tests__'),
@@ -133,7 +179,6 @@ module.exports = yeoman.generators.NamedBase.extend({
           nodir: false
         }
       );
-
       var packageJSONPath = path.join(
         this.destinationRoot(),
         'package.json'

react-native-cli/index.js

@@ -38,6 +38,7 @@
 var fs = require('fs');
 var path = require('path');
 var exec = require('child_process').exec;
+var execSync = require('child_process').execSync;
 var spawn = require('child_process').spawn;
 var chalk = require('chalk');
 var prompt = require('prompt');
@@ -74,6 +75,33 @@ var REACT_NATIVE_PACKAGE_JSON_PATH = function() {
   );
 };
 
+// Use Yarn if available, it's much faster than the npm client.
+// Return the version of yarn installed on the system, null if yarn is not available.
+function getYarnVersionIfAvailable() {
+  let yarnVersion;
+  try {
+    // execSync returns a Buffer -> convert to string
+    if (process.platform.startsWith('win')) {
+      yarnVersion = (execSync('yarn --version').toString() || '').trim();
+    } else {
+      yarnVersion = (execSync('yarn --version 2>/dev/null').toString() || '').trim();
+    }
+  } catch (error) {
+    return null;
+  }
+  // yarn < 0.16 has a 'missing manifest' bug
+  try {
+    if (semver.gte(yarnVersion, '0.16.0')) {
+      return yarnVersion;
+    } else {
+      return null;
+    }
+  } catch (error) {
+    console.error('Cannot parse yarn version: ' + yarnVersion);
+    return null;
+  }
+}
+
 checkForVersionArgument();
 
 var cli;
@@ -102,8 +130,8 @@ if (cli) {
       );
       process.exit(1);
     } else {
-      if (!argv.verbose) console.log('This may take some time...');
+      const rnPackage = argv.version;
-      init(commands[1], argv.verbose, argv.version);
+      init(commands[1], argv.verbose, rnPackage, argv.npm);
     }
     break;
   default:
@@ -117,7 +145,7 @@ if (cli) {
   }
 }
 
-function validatePackageName(name) {
+function validateProjectName(name) {
   if (!name.match(/^[$A-Z_][0-9A-Z_$]*$/i)) {
     console.error(
       '"%s" is not a valid name for a project. Please use a valid identifier ' +
@@ -137,17 +165,24 @@ function validatePackageName(name) {
   }
 }
 
-function init(name, verbose, rnPackage) {
+/**
-  validatePackageName(name);
+ * @param name Project name, e.g. 'AwesomeApp'.
+ * @param verbose If true, will run 'npm install' in verbose mode (for debugging).
+ * @param rnPackage Version of React Native to install, e.g. '0.38.0'.
+ * @param forceNpmClient If true, always use the npm command line client,
+ *                       don't use yarn even if available.
+ */
+function init(name, verbose, rnPackage, forceNpmClient) {
+  validateProjectName(name);
 
   if (fs.existsSync(name)) {
-    createAfterConfirmation(name, verbose, rnPackage);
+    createAfterConfirmation(name, verbose, rnPackage, forceNpmClient);
   } else {
-    createProject(name, verbose, rnPackage);
+    createProject(name, verbose, rnPackage, forceNpmClient);
   }
 }
 
-function createAfterConfirmation(name, verbose, rnPackage) {
+function createAfterConfirmation(name, verbose, rnPackage, forceNpmClient) {
   prompt.start();
 
   var property = {
@@ -160,7 +195,7 @@ function createAfterConfirmation(name, verbose, rnPackage) {
 
   prompt.get(property, function (err, result) {
     if (result.yesno[0] === 'y') {
-      createProject(name, verbose, rnPackage);
+      createProject(name, verbose, rnPackage, forceNpmClient);
     } else {
       console.log('Project initialization canceled');
       process.exit();
@@ -168,7 +203,7 @@ function createAfterConfirmation(name, verbose, rnPackage) {
   });
 }
 
-function createProject(name, verbose, rnPackage) {
+function createProject(name, verbose, rnPackage, forceNpmClient) {
   var root = path.resolve(name);
   var projectName = path.basename(root);
 
@@ -192,20 +227,18 @@ function createProject(name, verbose, rnPackage) {
   fs.writeFileSync(path.join(root, 'package.json'), JSON.stringify(packageJson));
   process.chdir(root);
 
-  console.log('Installing react-native package from npm...');
-
   if (verbose) {
-    runVerbose(root, projectName, rnPackage);
+    runVerbose(root, projectName, rnPackage, forceNpmClient);
   } else {
-    run(root, projectName, rnPackage);
+    run(root, projectName, rnPackage, forceNpmClient);
   }
 }
 
 function getInstallPackage(rnPackage) {
   var packageToInstall = 'react-native';
-  var valideSemver = semver.valid(rnPackage);
+  var isValidSemver = semver.valid(rnPackage);
-  if (valideSemver) {
+  if (isValidSemver) {
-    packageToInstall += '@' + valideSemver;
+    packageToInstall += '@' + isValidSemver;
   } else if (rnPackage) {
     // for tar.gz or alternative paths
     packageToInstall = rnPackage;
@@ -213,23 +246,36 @@ function getInstallPackage(rnPackage) {
   return packageToInstall;
 }
 
-function run(root, projectName, rnPackage) {
+function run(root, projectName, rnPackage, forceNpmClient) {
-  exec('npm install --save --save-exact ' + getInstallPackage(rnPackage), function(e, stdout, stderr) {
+  const yarnVersion = (!forceNpmClient) && getYarnVersionIfAvailable();
-    if (e) {
+  let installCommand;
+  if (yarnVersion) {
+    console.log('Using yarn v' + yarnVersion);
+    console.log('Installing ' + getInstallPackage(rnPackage) + '...');
+    installCommand = 'yarn add ' + getInstallPackage(rnPackage) + ' --exact';
+  } else {
+    console.log('Installing ' + getInstallPackage(rnPackage) + ' from npm...');
+    if (!forceNpmClient) {
+      console.log('Consider installing yarn to make this faster: https://yarnpkg.com');
+    }
+    installCommand = 'npm install --save --save-exact ' + getInstallPackage(rnPackage);
+  }
+  exec(installCommand, function(err, stdout, stderr) {
+    if (err) {
       console.log(stdout);
       console.error(stderr);
-      console.error('`npm install --save --save-exact react-native` failed');
+      console.error('Command `' + installCommand + '` failed.');
       process.exit(1);
     }
-
     checkNodeVersion();
-
     cli = require(CLI_MODULE_PATH());
     cli.init(root, projectName);
   });
 }
 
-function runVerbose(root, projectName, rnPackage) {
+function runVerbose(root, projectName, rnPackage, forceNpmClient) {
+  // Use npm client, yarn doesn't support --verbose yet
+  console.log('Installing ' + getInstallPackage(rnPackage) + ' from npm. This might take a while...');
   var proc = spawn(/^win/.test(process.platform) ? 'npm.cmd' : 'npm', ['install', '--verbose', '--save', '--save-exact', getInstallPackage(rnPackage)], {stdio: 'inherit'});
   proc.on('close', function (code) {
     if (code !== 0) {

react-native-cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-native-cli",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "license": "BSD-3-Clause",
   "description": "The React Native CLI tools",
   "main": "index.js",