Add yarn

README.md

@@ -1,15 +1,15 @@
 npm-cache
 =========
 
-`npm-cache` is a command line utility that caches dependencies installed via `npm`, `bower`, `jspm` and `composer`.
+`npm-cache` is a command line utility that caches dependencies installed via `npm`, `bower`, `jspm`, `composer` and `yarn`.
 
-It is useful for build processes that run `[npm|bower|composer|jspm] install` every time as part of their 
+It is useful for build processes that run `[npm|bower|composer|jspm|yarn] install` every time as part of their 
 build process. Since dependencies don't change often, this often means slower build times. `npm-cache`
 helps alleviate this problem by caching previously installed dependencies on the build machine. 
 `npm-cache` can be a drop-in replacement for any build script that runs `[npm|bower|composer|jspm] install`. 
 
 ## How it Works
-When you run `npm-cache install [npm|bower|jspm|composer]`, it first looks for `package.json`, `bower.json`,
+When you run `npm-cache install [npm|bower|jspm|composer|yarn]`, it first looks for `package.json`, `bower.json`,
 or `composer.json` in the current working directory depending on which dependency manager is requested.
 It then calculates the MD5 hash of the configuration file and looks for a filed named 
 <MD5 of config.json>.tar.gz in the cache directory ($HOME/.package_cache by default). If the file does not

cacheDependencyManagers/yarnConfig.js

@@ -0,0 +1,51 @@
+'use strict';
+
+var path = require('path');
+var shell = require('shelljs');
+var fs = require('fs');
+var md5 = require('md5');
+var logger = require('../util/logger');
+var isUsingYarnLock = null;
+
+
+// Returns path to configuration file for yarn. Uses
+// yarn.lock
+var getYarnConfigPath = function () {
+  var yarnLockPath = path.resolve(process.cwd(), 'yarn.lock');
+  var packageJsonPath = path.resolve(process.cwd(), 'package.json');
+
+  if (isUsingYarnLock === null) {
+      if (fs.existsSync(yarnLockPath)) {
+          logger.logInfo('[yarn] using yarn.lock instead of package.json');
+          isUsingYarnLock = true;
+      }  else {
+          isUsingYarnLock = false;
+      }
+  }
+
+  return isUsingYarnLock ? yarnLockPath : packageJsonPath;
+};
+
+function getFileHash(filePath) {
+  if (isUsingYarnLock) {
+      var yarnlockfile = fs.readFileSync(filePath);
+      return md5(yarnlockfile);
+  } else {
+      var json = JSON.parse(fs.readFileSync(filePath));
+      return md5(JSON.stringify({
+          dependencies: json.dependencies,
+          devDependencies: json.devDependencies
+      }));
+  }
+}
+
+module.exports = {
+  cliName: 'yarn',
+  getCliVersion: function getYarnVersion () {
+    return shell.exec('yarn --version', {silent: true}).output.trim();
+  },
+  configPath: getYarnConfigPath(),
+  installDirectory: 'node_modules',
+  installCommand: 'yarn',
+  getFileHash: getFileHash
+};

util/logger.js

@@ -5,6 +5,7 @@ exports.logError = function (errorMessage) {
 };
 
 exports.logInfo = function (message) {
-  console.log('[npm-cache] [INFO] ' + message);
+    var date = new Date();
+    console.log('[npm-cache] [INFO] ' + date.getHours() + ':' + date.getMinutes() + ':' + date.getSeconds() + ' ' + message);
 };