Ransack is a great gem. You can consider it as a new better (with sparkles!) version of MetaSearch. Unfortunately, it seems that it is not translating ActiveRecord attributes, when they are nested.
For example:

module System
  class Setting < ActiveRecord::Base
    validates :name,
      presence: true
  end
end

We have a name attribute on a System::Setting model. According to Rails doc translation yaml for such a structure should be similar to this one:

pl:
  activerecord:
    attributes:
      "system/setting":
        name: Nazwa

Unluckily this won’t work (it did with MetaSearch). When you look into Ransack /lib/ransack/translate.rb file, you will find such a piece of code (around line 25):

defaults = base_ancestors.map do |klass|
  :"ransack.attributes.#{klass.model_name.singular}.#{original_name}"
end

You can see, that Ransack is enclosing all attributes in it’s own namespace. I can’t do this, since I have gems that use “original” Rails convention (activerecord.attributes), so I had to replace those lines with:

defaults  = []
base_ancestors.map do |klass|
  defaults << :"activerecord.attributes.#{klass.model_name.i18n_key}.#{original_name}"
  defaults << :"ransack.attributes.#{klass.model_name.singular}.#{original_name}"
end

After that, Ransack is supporting both namespaces. The whole translate file that you should include in your project should look like this:

I18n.load_path += Dir[File.join(File.dirname(__FILE__), 'locale', '*.yml')]

# This is a temporary workaround for this issue:
# https://github.com/ernie/ransack/issues/273
# It allows names to be translated in sort_link @search, :name based on their
# activerecord.attributes scope
module Ransack
  module Translate
    def self.attribute(key, options = {})
      unless context = options.delete(:context)
        raise ArgumentError, "A context is required to translate attributes"
      end

      original_name = key.to_s
      base_class = context.klass
      base_ancestors = base_class.ancestors.select { |x| x.respond_to?(:model_name) }
      predicate = Predicate.detect_from_string(original_name)
      attributes_str = original_name.sub(/_#{predicate}$/, '')
      attribute_names = attributes_str.split(/_and_|_or_/)
      combinator = attributes_str.match(/_and_/) ? :and : :or
      defaults  = []
      base_ancestors.map do |klass|
        defaults << :"activerecord.attributes.#{klass.model_name.i18n_key}.#{original_name}"
        defaults << :"ransack.attributes.#{klass.model_name.singular}.#{original_name}"
      end

      translated_names = attribute_names.map do |attr|
        attribute_name(context, attr, options[:include_associations])
      end

      interpolations = {}
      interpolations[:attributes] = translated_names.join(" #{Translate.word(combinator)} ")

      if predicate
        defaults << "%{attributes} %{predicate}"
        interpolations[:predicate] = Translate.predicate(predicate)
      else
        defaults << "%{attributes}"
      end

      defaults << options.delete(:default) if options[:default]
      options.reverse_merge! :count => 1, :default => defaults
      I18n.translate(defaults.shift, options.merge(interpolations))
    end

  end
end