M lib/github/markup.rb → lib/github/markup.rb

@@ -31,10 +31,9 @@ if File.exists?(file = File.dirname(__FILE__) + "/commands/#{command}")
         command = file
       end
 
-      return if !system("which #{command} > /dev/null")
-
       add_markup(regexp) do |content|
         rendered = execute(command, content)
+        rendered = rendered.to_s.empty? ? content : rendered
         block ? block.call(rendered) : rendered
       end
     end
@@ -64,6 +63,8 @@ stdin.close
         out = stdout.read
       end
       out.gsub("\r", '')
+    rescue Errno::EPIPE
+      ""
     end
 
     # Define markups

M test/markup_test.rb → test/markup_test.rb

@@ -30,7 +30,7 @@
   def test_fails_gracefully_on_missing_commands
     GitHub::Markup.command(:i_made_it_up, /mde/)
     text = 'hi there'
-    assert_equal false, GitHub::Markup.can_render?('README.mde')
+    assert GitHub::Markup.can_render?('README.mde')
     actual = GitHub::Markup.render('README.mde', text)
     assert_equal text, actual
   end
@@ -38,7 +38,7 @@
   def test_fails_gracefully_on_missing_env_commands
     GitHub::Markup.command('/usr/bin/env totally_fake', /tf/)
     text = 'hey mang'
-    assert_equal false, GitHub::Markup.can_render?('README.tf')
+    assert GitHub::Markup.can_render?('README.tf')
     actual = GitHub::Markup.render('README.tf', text)
     assert_equal text, actual
   end