i18n_key for derived record is the same as parent record

[fsateler]

Which creates pollution for the base class translations.

The setup

en:
  activerecord:
    attributes:
      some_record_extended:
        new_attribute: My Fancy Attribute

class SomeRecord < ActiveRecord::Base
end

class SomeRecordExtended < ActiveType::Record[::SomeRecord]
  attr_accessor :new_attribute
end

Expected Result

SomeRecordExtended.human_attribute_name :new_attribute # => 'My Fancy Attribute'

Actual Result

SomeRecordExtended.human_attribute_name :new_attribute # => 'New attribute'

Investigation

Turns out that ActiveType::RecordExtension::Inheritance simply delegates model_name to the base record class:

active_type/lib/active_type/record_extension/inheritance.rb

Lines 30 to 32 in 0973a8f

	def model_name
	extended_record_base_class.model_name
	end

AFAICT, this necessary because it is desired that param_key and friends be the same. However, this has the problem that i18n_key is the same too:

SomeRecord.model_name.i18n_key # => 'some_record'
SomeRecordExtended.model_name.i18n_key # => 'some_record'

This results in having to declare the extended properties in the translation for the base record class, which is confusing and pollutes the translations.

Solutions

My first local hack was to do this:

def self.model_name
  super.tap{|n| n.instance_variable_set(:@i18n_key, name.underscore) }
end

Which is of course super hacky. An alternative would be to create a Name subclass:

class ActiveTypeName < ActiveModel::Name
  def initialize(klass, extended_record_base_klass)
    super(extended_record_base_klass)
    @i18n_key = klass.name.underscore
  end

  attr_reader :i18n_key # Redefine to avoid depending on internal rails behavior
end

and then redefine model_name:

def model_name
   @model_name ||= ActiveTypeName.new(self, extended_record_base_class)
end

A third alternative would be to monkey_patch i18n_key:

def model_name
   @model_name ||= begin
     dup_model_name = extended_record_base_class.model_name.dup
     key = name.underscore
     dup_model_name.define_singleton_method(:i18n_key) { key }
     dup_model_name
   end
end

[fsateler]

I've posted a PR implementing the third option. Seems like the less intrusive to me.