nestedvalidation.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var assert = require('assert')
mongoose.connect('localhost', 'testing_findone');

var schema = new Schema({
  name: { last: { type: String, required: true} }
});

var A = mongoose.model('A', schema);

mongoose.connection.on('open', function () {
  A.findOne({}, ['name'], function (err, doc) {
    if (err) console.error(err.stack||err);
    assert.equal(null, doc);
    console.error('all good');

    mongoose.connection.db.dropDatabase(function () {
      mongoose.connection.close();
    });
  });
});

This is my next issue, custom validation functions are still called on fields which are not selected.

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var assert = require('assert')
mongoose.connect('localhost', 'testing_findone');
var schema = new Schema({
  name: {
    type: String,
    required: true,
    validate: [function(str) {
        return str.length < 20;
    }, 'MaxLength']
  },
  nick: {
    type: String,
    required: true
  },
  soemthing: String
}, {strict: true});

var A = mongoose.model('A', schema);

mongoose.connection.on('open', function () {
  var a = new A({
    name: 'name',
    nick: 'nick'
  });
  a.save(function(err) {
    assert.equal(null, err);

    A.findOne({},['nick'], function (err, doc) {
      if (err) console.error(err.stack||err);
      console.log('"name" in doc should be false but it is - ', 'name' in doc);

      doc.nick = 'blubb';
      doc.save(function(err) {
        console.error(err);
        mongoose.connection.db.dropDatabase(function () {
          mongoose.connection.close();
        });
      });
    });

  });
});

please open a ticket on the repo. :)