discourse/app/views/list/list.rss.erb

<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <% lang = SiteSetting.find_by_name('default_locale').try(:value) %>
    <title><%= @title %></title>
    <link><%= @link %></link>
    <description><%= @description %></description>
    <% if lang %>
      <language><%= lang %></language>
    <% end %>
    <lastBuildDate><%= @topic_list.topics.first.created_at.rfc2822 %></lastBuildDate>
    <atom:link href="<%= @atom_link %>" rel="self" type="application/rss+xml" />
    <% @topic_list.topics.each do |topic| %>
      <% topic_url = Discourse.base_url + topic.relative_url -%>
      <item>
        <title><%= topic.title %></title>
        <author><%= "@#{topic.user.username} (#{topic.user.name})" -%></author>
        <category><%= topic.category.name %></category>
        <description><![CDATA[
          <p><%= t('author_wrote', author: link_to(topic.user.name, topic.user)).html_safe %></p>
          <blockquote>
            <%= topic.posts.first.cooked.html_safe %>
          </blockquote>
          <p><%= t 'num_posts' %> <%= topic.posts_count %></p>
          <p><%= t 'num_participants' %> <%= topic.participant_count %></p>
          <p><%= link_to t('read_full_topic'), topic_url %></p>
        ]]></description>
        <link><%= topic_url %></link>
        <pubDate><%= topic.created_at.rfc2822 %></pubDate>
        <guid><%= topic_url %></guid>
        <source url="<%= topic_url %>.rss"><%= topic.title %></source>
      </item>
    <% end %>
  </channel>
</rss>