Deal with bitmask-form options & Safely monkey patch Ruby gems

constant_gardener.rb

class ConstantGardener
  
  def self.create(*booleans)
    Class.new do
      def initialize(bitmask)
        @bitmask = bitmask
      end
      
      booleans.each_with_index do |b, i|
        const_set b.to_s.upcase, 2**i
        define_method "#{b.to_s.downcase}?" do
          @bitmask[i] == 1
        end
      end
    end
  end
  
end

gem_patch.rb

require 'rubygems'
require 'constant_gardener'

module GemPatch  
  Strategy = ConstantGardener.create(:warn, :skip, :raise)
  
  class << self
    private
    def versions_to_sentence(versions)
      if versions.size == 1
        "version #{versions.first}"
      else
        "versions " + versions[0..-2].join(', ') + " and " + versions.last.to_s
      end
    end
  end
end

class GemPatchError < StandardError; end

module Kernel
  def patch(gem_spec, strategy = GemPatch::Strategy::RAISE, &block)
    name, *versions = gem_spec.split(/\s+/)
    wanted_versions = versions.map{ |v| Gem::Version.new(v) }
    loaded_version = Gem.loaded_specs[name] ? Gem.loaded_specs[name].version : nil
    strategy = GemPatch::Strategy.new(strategy)

    error = if !loaded_version
      "You patched #{name} in #{caller.first} but #{name} was not loaded."
    elsif wanted_versions.size > 0 && !wanted_versions.include?(loaded_version)
      "You patched #{name} #{GemPatch.send(:versions_to_sentence, wanted_versions)} in #{caller.first} but version #{loaded_version} was loaded. Is your patch still applicable?"
    end

    raise GemPatchError, error if error && strategy.raise?
    logger.warn "GemPatch warning: #{error}" if error && respond_to?(:logger) && strategy.warn?
    yield unless error && strategy.skip?
  end
end

usage.rb

require 'gem_patch'

# Raises an error if faker isn't loaded:
#
patch "faker" do
  
  module Faker
    #...
  end
  
end

# Logs a warning if a version of faker other than 0.3.0 is loaded:
# 
patch "faker 0.3.0", GemPatch::Strategy::WARN do
  
  module Faker
    #...
  end
  
end

# Logs a warning and does not apply the patch if a version of faker other
# than 0.2.9 or 0.3.0 is loaded:
# 
patch "faker 0.2.9 0.3.0", GemPatch::Strategy::WARN + GemPatch::Strategy::SKIP do
  
  module Faker
    #...
  end
  
end