In some wonkiness / fairness, in 3.8.0 persisted? is in fact true before saving; it just did a put item anyway.

Edit: also, as expected, writing an entirely new object to the field works. Writing the same object does not. Added more tests to the example.

Haven't tested it but I'm now thinking this applies to hash fields (without any adapter) too? Anything that doesn't go through a dynamo field= (or update_attribute, etc) method.

I can confirm that my custom datatype also doesn't update on Version 3.9, but does on 3.8.

registration = Registrations.find("#{competition_id}-#{user_id}")
updated_lanes = registration.lanes.map { |lane|
  if lane.name == "Competing"
    lane.lane_state = "deleted"
  end
  lane
}
puts updated_lanes.to_json # Updated here
updated_registration = registration.update_attributes!(lanes: updated_lanes) # Updated here
# But not updated in the database

There is also no PUT call in the Console Output.
My model has a field :lanes, :array, of: Lane

and Lane looks like this

class Lane
  attr_accessor :name, :lane_state, :completed_steps, :step_details

  def initialize(args)
    @name = args["name"]
    @lane_state = args["lane_state"] || "waiting"
    @completed_steps = args["completed_steps"] || []
    @step_details = args["step_details"] || {}
  end

  def dynamoid_dump
    self.to_json
  end

  def self.dynamoid_load(serialized_str)
    parsed = JSON.parse serialized_str
    Lane.new(parsed)
  end
end

It looks like as an overlooked broken change. Thank you for the report.

I suppose the expected behaviour is (at saving already persisted model) to persist all the attributes unconditionally if there is a field with custom type (field adapter), but not only changed/"dirty" attributes (like in works since 3.9.0)

@andrykonchin Is this fixed in 3.10?

No, it isn't fixed yet.

Haven't tested it but I'm now thinking this applies to hash fields (without any adapter) too? Anything that doesn't go through a dynamo field= (or update_attribute, etc) method.

I'm also seeing failure to update using update_attribute directly and by using field= approach. Downgrading to v3.8.0 is the only solution.

@jufemaiz Could you please provide examples of code that don't work as expected to save an attribute new value with update_attribute and <field>= setter to reproduce the issue?

@jufemaiz Could you please provide examples of code that don't work as expected to save an attribute new value with update_attribute and <field>= setter to reproduce the issue?

I'll work on an example that's not dependent on internal repos.