instance.save() doesn't detect and save changes in arrays or objects

Consider following schema

var Model = sequelize.define('model', {
    array: Sequelize.ARRAY(Sequelize.INTEGER)
});

and following code

Model.create({
  array: [1],
}).then(function(instance) {

  instance.array.push(2);
  instance.save().then(function() {

    instance.reload().then(function() {
      console.log(instance.array);
    });

  });
});

instance.array outputs [1], but I expect it to be [1,2].

Documentation states that When you call save without changing any attribute, this method will execute nothing, but I’m guessing only object references are being checked and not the actual values.

Same issue can be reproduced with Sequelize.JSONB type as well.

[adamjaffeback]

This issue had me thinking I was crazy for a good 30 minutes. I’d like to submit a PR to improve the API documentation, but I’m not sure on the wording. Please review a draft:

Original

Validate this instance, and if the validation passes, persist it to the database. It will only save changed fields, and do nothing if no fields have changed.

On success, the callback[…]

Replacement

[…] do nothing if no fields have changed.

Note: If a JSON/JSONB attribute is called with a dot.seperated key, it will flag the entire object as changed. Changes to ARRAY types do not set a flag as changed and will not be persisted with save; use update instead.

instance.dogs;
// ['lab', 'poodle']

// Wrong
instance.dogs.pop();
instance.dogs;
// ['lab']
instance.save()
.then(function(savedInstance) {
  savedInstance.dogs;
  // ['lab', 'poodle']
  // no change flag, no persistence
});

// Correct Usage
instance.update({ dogs: ['lab'] })
.then(function(updatedInstance) {
  updatedInstance.dogs;
  // ['lab']
  // persistence
});

On success, the callback[…]

[jcalfee]

I think I figured it out. It looks like Sequelize is doing an equality check ===, so I can clone the array b = [...a || []] or just b = [...a] then if I change the clone I assign the cloned array back to the model and it saves. There was no need to add additional Sequelize method calls to do this.