feat(cli): install necessary packages for default gulpfile

After downloading the default gulpfile, install the necessary packages
for it to work.

Author: tlancina

lib/cli.js

@@ -198,23 +198,28 @@ function runWithGulp(argv, taskInstance){
       });
       var downloadGulp = false;
       return deferred.promise.then(
-        function(){
+        function() {
           downloadGulp = true;
-          return downloadDefaultGulpfile();
+          return downloadDefaultGulpfile(cmdName).then(
+            installGulpfilePackages,
+            function(err) {
+              console.error('There was an error downloading the default gulpfile: ' + err);
+              process.exit(1);
+            }
+          ).then(
+            function(){
+              console.success('Npm packages installed successfully. Try running \'' + cmdName + '\' again.');
+            },
+            function(){
+              console.warn('There was an error installing the packages required by the gulpfile.');
+              console.warn('You\'ll need to install the following packages manually: ');
+              console.warn('    ' + requires.join(' '));
+            }
+          );
         },
-        function(){
+        function() {
           return Q.fcall(taskInstance.run.bind(taskInstance), Cli, argv);
         }
-      ).then(
-        function(){
-          if (downloadGulp) {
-            console.success('Successfully downloaded gulpfile. Try running \'' + cmdName + '\' again.');
-          }
-        },
-        function(err) {
-          console.error('There was an error downloading the default gulpfile: ' + err);
-          process.exit(1);
-        }
       );
     }
   }
@@ -254,7 +259,7 @@ function downloadDefaultGulpfile(){
   var branch = project.get('typescript') ? 'typescript' : 'master';
   var url = 'https://raw.githubusercontent.com/driftyco/ionic2-app-base/' + branch + '/gulpfile.js';
 
-  console.info(('Downloading default gulpfile from: ' + url));
+  console.info('\nDownloading default gulpfile from: ' + url);
 
   fileStream.on('open', function () {
     https.get(url, function (res) {
@@ -273,6 +278,26 @@ function downloadDefaultGulpfile(){
   return deferred.promise;
 }
 
+function installGulpfilePackages(cmdName){
+  var detective = require('detective');
+  var requires = detective(fs.readFileSync('gulpfile.js'));
+  var deferred = Q.defer();
+
+  console.success('Successfully downloaded gulpfile.\n');
+  console.info('Now installing npm packages used by the gulpfile: ');
+  console.info('    ' + requires.join(' ') + '\n');
+
+  var npmInstall = require('child_process').spawn('npm', ['install', '--save-dev'].concat(requires));
+  npmInstall.stdout.on('data', function(data){ logging.logger.debug(data) });
+  npmInstall.stderr.on('data', function(data){ logging.logger.debug(data) });
+  npmInstall.on('error', function(err) { console.error(err) });
+  npmInstall.on('exit', function(code) {
+    code !== 0 ? deferred.reject() : deferred.resolve();
+  });
+
+  return deferred.promise;
+}
+
 
 function logEvents(gulpInst, finalTaskNames) {
   gulpInst.on('task_start', function(e) {

package.json

@@ -67,6 +67,7 @@
     "connect-livereload": "0.5.2",
     "crc": "3.2.1",
     "cross-spawn": "0.2.3",
+    "detective": "4.3.1",
     "event-stream": "3.0.20",
     "expand-tilde": "1.2.0",
     "finalhandler": "0.2.0",