Can't push to array using mongoose

Question

I have code, basically still the MEANJS boilerplate, and I added a section to the articles for commenting. My strategy for the comments was to expose a route in express, /comments/:commentId, with a very simple comment model (it has a user object, a content string, and a likes number). I extended the article model to include an array of object IDs for the comments, and when an article was loaded, my angular resources would make a call to the /comments/:commentId to retrieve the list of comments specified by the array. Following is my server code

/* below is comments.server.controller.js */

/* THIS IS NEVER GETTING CALLED */
exports.updateArticleComments = function(req, res){
  Article.findById(req.comment.article).populate('user', 'displayName').exec(function(err, article){
    console.log(article);
    if (err) return res.json(err);
    if (!article) res.json({err: 'oops!'}); //handle this ish
    article.comments[article.comments.length] = req.comment._id;
    article.save(function(err, article){
      if (err){
        console.log('error');
      } else {
        res.json(article);
      }
    });
  });
};

exports.commentsByID = function(req, res, next, id) {
  Comment.findById(id).populate('user', 'displayName').exec(function(err, comment) {
    if (err) return next(err);
    if (!comment) return next(new Error('Failed to load comment ' + id));
    req.comment = comment;
    next();
  });
};

/* end comments.server.controller.js */

/* begin articles.server.routes.js */

'use strict';

/**
 * Module dependencies.
 */
var users = require('../../app/controllers/users.server.controller'),
  articles = require('../../app/controllers/articles.server.controller'),
  comments = require('../../app/controllers/comments.server.controller');

module.exports = function(app) {
  // Article Routes
  app.route('/articles')
    .get(articles.list)
    .post(users.requiresLogin, articles.create);

  app.route('/articles/:articleId')
    .get(articles.read)
    .put(users.requiresLogin, articles.hasAuthorization, articles.update)
    .post(comments.createComment, comments.updateArticleComments)
    .delete(users.requiresLogin, articles.hasAuthorization, articles.delete);

  // Finish by binding the article middleware
  app.param('articleId', articles.articleByID);
};

/* end articles.server.routes.js */

Everything, and I mean everything, works, EXCEPT exports.updateArticleComments function. I have seriously written about 5 different function, trying lodash's _extend, and many other techniques. I can't figure out why the comments array is never being filled. Does anyone have any suggestions at all?

EDIT: was requested to share createComment, so here it is

exports.createComment = function(req, res, next){
  var comment = new Comment({content: req.body.content, article: req.body.articleId});
  comment.user = req.user;
  comment.save(function(comment, err){
    if (err){
       return res.jsonp(err);
    } else {
        req.comment = comment;
        next();
    }
  });
};

Answer 1

Article.update({_id: 'VAL' }, {
  $push: { 
    'comments' : req.comment._id }},{upsert:true},
    function(err, data) { });

Have you tried the push method? I'd also be curious if the value of comment _id is coming back and not undefined.