Test case for mongoose 3.5.4 that fails saving a subdocument retrieved via projection when saving. Saves to the wrong array element.

mongooseprojectiontest.js

var mongoose = require('mongoose');
mongoose.set('debug', true);
var mongooseConnection = mongoose.createConnection('mongodb://localhost/mongooseprojectiontest');
 
var SubDocSchema = new mongoose.Schema({
    someValue: { type: Number },
},{
    versionKey: false
});
 
var DocSchema = new mongoose.Schema({
    someId: { type: Number },    
    subDocs: [SubDocSchema],
});
 
var Doc = mongooseConnection.model('Doc', DocSchema)
var main = new Doc({
    someId: 1,
    subDocs: [{ someValue: 1 },{ someValue: 2 },{ someValue: 3 }]
});
main.save(function(err) {
    if (err) { return console.log(err); }
    Doc.findOne({someId: 1}, { subDocs: { $elemMatch: { someValue: 3}}}, function(err, doc){
        if (err) { return console.log(err); }
 
        for (var i = 0; i < doc.subDocs.length; i++) {
            if (doc.subDocs[i].someValue == 3) {
                doc.subDocs[i].someValue = 4;
            }
        }
 
        doc.save(function(err) {
            if (err) { return console.log(err); }
        });
    });
});