Add a nofollow filter for links

Author: nono

lib/html/pipeline.rb

@@ -31,6 +31,7 @@ class Pipeline
     autoload :TableOfContentsFilter, 'html/pipeline/toc_filter'
     autoload :SVGTeX,                'html/pipeline/svgtex'
     autoload :SyntaxHighlightFilter, 'html/pipeline/syntax_highlight_filter'
+    autoload :NoFollowLinksFilter,   'html/pipeline/no_follow_links_filter'
     autoload :RelativeLinksFilter,   'html/pipeline/relative_links_filter'
     autoload :CustomLinksFilter,     'html/pipeline/custom_links_filter'
     autoload :SanitizationFilter,    'html/pipeline/sanitization_filter'

lib/html/pipeline/linuxfr.rb

@@ -1,4 +1,3 @@
-# encoding: utf-8
 module HTML
   class Pipeline
 
@@ -8,20 +7,21 @@ class LinuxFr
         toc_header: "<h2 class=\"sommaire\">Sommaire</h2>\n",
         svgtex_url: "http://localhost:16000",
         host: "linuxfr.org"
-      }
+      }.freeze
 
-      def self.render(text)
+      def self.render(text, context = {})
         pipeline = HTML::Pipeline.new [
           HTML::Pipeline::SVGTeX::PreFilter,
           HTML::Pipeline::MarkdownFilter,
           HTML::Pipeline::SanitizationFilter,
           HTML::Pipeline::TableOfContentsFilter,
           HTML::Pipeline::SVGTeX::PostFilter,
           HTML::Pipeline::SyntaxHighlightFilter,
+          HTML::Pipeline::NoFollowLinksFilter,
           HTML::Pipeline::RelativeLinksFilter,
           HTML::Pipeline::CustomLinksFilter,
         ], CONTEXT
-        result = pipeline.call text
+        result = pipeline.call text, context
         result[:output].to_s
       end
 

lib/html/pipeline/no_follow_links_filter.rb

@@ -0,0 +1,20 @@
+module HTML
+  class Pipeline
+
+    # Add rel="nofollow" to <a> links if enabled in the context to avoid giving
+    # SEO juice to potential spam links.
+    class NoFollowLinksFilter < Filter
+
+      def call
+        return doc unless context[:nofollow]
+
+        doc.css("a[href]").each do |element|
+          element['rel'] = 'nofollow'
+        end
+        doc
+      end
+
+    end
+
+  end
+end