We recently ran into an issue with one of our older websites that uses Radiant CMS 0.8. This version of Radiant uses Rails 2.3.4, which hardcodes a dependency on Rack 1.0.0. This can be very obnoxious that we're using Rails 2.3.9 and 3.0 for our newer projects, which utilize higher versions of Rack.
Since we have newer versions of Rack installed on our development system, we'd get something like this:
/Library/Ruby/Site/1.8/rubygems.rb:280:in `activate': can't activate rack (~> 1.0.0, runtime) for , already activated rack-1.1.0 for ["radiant-0.8.1"] (Gem::LoadError)
One option is to uninstall higher versions of Rack (booooo), but another, better reason, is to use Bundler to define our environment.
The Bundler website has an excellent page for adding Bundler support to older versions of Rails (< 3.0). Do that first in your Radiant CMS site directory. The Gemfile that I used is:
And then, from ever after, I run my copy of the Radiant site locally by prefixing commands with "bundler exec". i.e.:
bunder exec script/server