Refactor example of donejs/cli

refactor-example.js

// OLD

// Returns a .then-able function that installs a single module
// if it is not available in the current path
var installIfMissing = exports.installIfMissing = function(root, module, range) {
  var location = module ? path.join(root, module) : root;
  if(!module) {
    module = root;
  }

  debug('Looking for and installing if missing', module);

  return function() {
    try {
      return Q(require.resolve(location));
    } catch (e) {
      if(range) {
        module = module + '@' + range;
      }
      console.log('Installing ' + module);
      return runCommand('npm', ['install', module, '--loglevel', 'error']);
    }
  };
};

// NEW

function ensurePackage (projectRoot, qualifiedName) {
  var packageName = qualifiedName.split('@');
  if (hasPackage(projectRoot, packageName)) {
    return Promise.resolve();
  }

  return installPackage(qualifiedName);
}

function hasPackage (projectRoot, name) {
  var packagesFolder = path.join(projectRoot, 'node_modules');
  var packageFolder = path.join(packagesFolder, name);
  try {
    require.resolve(packageFolder);
    return true;
  } catch (error) {
    return false;
  }
}

function installPackage (qualifiedName) {
  return runCommand('npm', ['install', qualifiedName, '--no-shrinkwrap', '--loglevel', 'error']);
}