gistfile1.rb

ActionController::Routing::Routes.draw do |map|
  map.with_options :path_prefix => '/:account_id' do |map|
     map.resources :collections
  end
end

module ActionView
  module Helpers
    module UrlHelper
      alias :real_url_for :url_for

      def url_for(options={})
        account_options = {:account_id => params[:account_id]}
        options.merge!(account_options) if options.is_a?(Hash)
        real_url_for(options)
      end
    end
  end
end

<%= link_to h(collection.name), collection %>

#collection_url failed to generate from {:action=>"show", :account_id=>"test", :controller=>"collections"}, expected: {:action=>"show", :controller=>"collections"}, diff: {:account_id=>"test"}