ActiveRecord locales (.yml) for Mongoid attribute validations

activerecord.yml

# config/locales/activerecord.yml

# Custom error messages for ActiveRecord and Mongoid Document validations.
#
# For a full list of validation options, see:
# http://guides.rubyonrails.org/i18n.html#translations-for-active-record-models
en:
  activerecord:
    errors:
      models:
        order:
          attributes:
            size:
              greater_than_or_equal_to: must be a positive number, dude.
            name:
              blank: cannot be let blank. Thanks!

application.rb

# config/application.rb

require_relative './mongoid_validations'

module ExampleApp
  class Application < Rails::Application
    config.after_initialize do
      MongoidValidations.set_validation_file
    end
  end
end

mongoid_validations.rb

# config/mongoid_validations.rb

module MongoidValidations
  # Point Mongoid Documents validations to use ActiveRecord validations
  # that rails uses from the locales/en.yml or locales/activerecord.yml
  def self.set_validation_file
    Rails.application.eager_load!

    Mongoid.models.each do |model|
      class << model
        def i18n_scope
          :activerecord
        end
      end
    end
  end
end

order.rb

# app/models/order.rb

# An example Mongoid Document
class Order
  include Mongoid::Document

  field :name, type: String
  field :size, type: Float, default: -> { 0.0 }

  validates :name, presence: true
  validates :size, numericality: { greater_than_or_equal_to: 0.0 }
end

Hey, I know this is a really old post, however, I found that just replacing active_record with mongoid on the config/locales/en.yml file works. Also, the quotes on the message seem to be necessary - I am using rails 5.1.4.