Rails XML builder with no pretty-printing (i.e. minified XML)

Answer 1

Calling Builder::XmlMarkup.new without any indent parameter at all shouldn’t give you any whitespace.

xml = Builder::XmlMarkup.new
xml.outertag do
  xml.list do
    # Some code which loops through a list
  end
end

xml # => <outertag><list></list></outertag>

Answer 2

Accepting Matt's answer as it seems the most generally-applicable. However since my situation is an API that outputs XML for every URL, I want something that works across the board.

Here are two solutions for that:

1. (My current solution) Make a simple plugin that monkey-patches ActionView::TemplateHandlers::Builder to force 0 indentation (as per Matt's answer). Unfortunately, ActionView::TemplateHandlers::Builder is mostly an opaque string of Ruby code that is eval()ed later. Here is my main module, which I include in:

   module MinimalXml
     module Builder
       def self.included(base)
         base.class_eval do
           def compile(template)
             indent = 0
             "_set_controller_content_type(Mime::XML);" +
               "xml = ::Builder::XmlMarkup.new(:indent => #{indent});" +
               "self.output_buffer = xml.target!;" +
               template.source +
               ";xml.target!;"
           end
         end
       end
     end
   end
   

2. (Probably a future solution.) It occurs to me that a serious XML-based web service needs to process incoming and outgoing XML, to validate it and do whatever else is necessary. That is a good candidate for Rack middleware. So eventually I foresee myself writing a simple Rack middleware layer which will validate the outgoing XML (sounding the alarm if it is invalid, etc.) and then either pretty-print it if in development mode, or compactify it in production.