dependency methods

dependencies.rb

#activesupport-3.0.5/lib/active_support/dependencies.rb
def require_dependency(file_name, message = "No such file to load -- %s")
   unless file_name.is_a?(String)
    raise ArgumentError, "the file name must be a String -- you passed #{file_name.inspect}"
  end

  Dependencies.depend_on(file_name, false, message)
end

def depend_on(file_name, swallow_load_errors = false, message = "No such file to load -- %s.rb")
  path = search_for_file(file_name)
  require_or_load(path || file_name)
rescue LoadError => load_error
  unless swallow_load_errors
    if file_name = load_error.message[/ -- (.*?)(\.rb)?$/, 1]
      raise LoadError.new(message % file_name).copy_blame!(load_error)
    end
    raise
  end
end

def search_for_file(path_suffix)
  path_suffix = path_suffix.sub(/(\.rb)?$/, ".rb")
  autoload_paths.each do |root|
    path = File.join(root, path_suffix)
    return path if File.file? path
  end
  nil # Gee, I sure wish we had first_match
end