discourse/app/controllers/extra_locales_controller.rb

class ExtraLocalesController < ApplicationController

  layout :false
  skip_before_filter :check_xhr, :preload_json

  def show
    bundle = params[:bundle]
    raise Discourse::InvalidAccess.new unless bundle =~ /^[a-z]+$/

    locale_str = I18n.locale.to_s
    translations = JsLocaleHelper.translations_for(locale_str)
    for_key = translations[locale_str]["#{bundle}_js"]

    if plugin_for_key = JsLocaleHelper.plugin_translations(locale_str)["#{bundle}_js"]
      for_key.deep_merge!(plugin_for_key)
    end

    js =
      if for_key.present?
        <<~JS
        (function() {
          if (window.I18n) {
            window.I18n.extras = window.I18n.extras || [];
            window.I18n.extras.push(#{for_key.to_json});
          }
        })();
        JS
      else
        ""
      end

    render text: js, content_type: "application/javascript"
  end
end