#!/usr/bin/env ruby

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'mongoid', '7.2.0'
end

require 'mongoid'

Mongoid.configure { |c| c.clients.default = { hosts: ['localhost'], database: 'test' } }
puts Mongoid::VERSION
puts Mongo::VERSION

# From https://github.com/mongodb/mongoid/blob/master/spec/mongoid/association/embedded/embeds_many_models.rb
class EmmCongress
  include Mongoid::Document
  include Mongoid::Timestamps

  embeds_many :legislators, class_name: 'EmmLegislator'

  field :name, type: String
end

class EmmLegislator
  include Mongoid::Document

  embedded_in :congress, class_name: 'EmmCongress'

  field :a, type: Integer, default: 0
  field :b, type: Integer, default: 0
end

# From https://github.com/mongodb/mongoid/blob/master/spec/mongoid/association/embedded/embeds_many_query_spec.rb

# setup
congress = EmmCongress.new(name: 'foo')
congress.legislators << EmmLegislator.new(a: 1, b: 2)
congress.save!

# let
congress = EmmCongress.where(name: 'foo').only(:id).first

p congress.legislators
# => what I expect: ActiveModel::MissingAttributeError
# => what is returned: []

# p congress.name
# in comparison, this is raising ActiveModel::MissingAttributeError as expeted

> ./mongoid_embeds_many_only.rb 
7.2.0
2.14.0
[]