I use rbenv and bundler, I want open the installed rails gem and insert some debug codes. So I run 'bundle show rails' in a rails project, I get '~/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/rails-3.2.11', but there is nothing in this directory.
Rails is just a meta-gem, as-in it doesn't contain any actual code, it just lists dependencies that make up Rails. This is why the gem's directory is empty.
If you want to edit part of the Rails code you should edit the relevant dependency. In a
Gemfile.lock the direct dependecies of Rails 3.2.11 are listed as follows:
rails (3.2.11) actionmailer (= 3.2.11) actionpack (= 3.2.11) activerecord (= 3.2.11) activeresource (= 3.2.11) activesupport (= 3.2.11) bundler (~> 1.0) railties (= 3.2.11)