mongoose-bug-set-pre-save-hook-with-select

index.js

'use strict';

//see https://github.com/Automattic/mongoose/issues/5800

const mongoose = require('mongoose');
const assert = require('assert');

mongoose.Promise = global.Promise;
mongoose.connect('mongodb://localhost/mongoose-gh-5800');

const MainSchema = new mongoose.Schema({
  a: {
    b: {type: String, default: 'some default'},
    c: {type: Number, default: 0},
    d: {type: String}
  },
  e: {type: String}
});

MainSchema
.pre('save', function(next) {
  if (this.isModified()) {
    //the expectation would be that only a.c is updated on save, not all of a
    this.set('a.c', 100, Number);
  }
  next();
});

const Main = mongoose.model('Main', MainSchema);


Main.remove({}, (err) => { //reset
  assert.ifError(err);
  Main.create({a: {b: 'not the default', d: 'some value'}, e: 'e'}, (err, m1) => { //create new document
    assert.ifError(err);
    console.log('m1', m1);
    assert.equal(m1.a.b, 'not the default');
    assert.equal(m1.a.d, 'some value');
    Main.findOne({}).select('e').exec((err, m1select) => { //load with subset of fields
      assert.ifError(err);
      m1select.e = 'e modified';
      m1select.save((err) => {
        assert.ifError(err);
        Main.findOne({}).exec((err, m1after) => { //load document again
          assert.ifError(err);
          console.log('m1after', m1after); //at this point a.d is missing and a.b is the default value
          assert.equal(m1after.a.b, 'not the default');
          assert.equal(m1after.a.d, 'some value');
          process.exit(0);
        });
      });
    });
  });
});