bundler_breakout.rb

# A small utility for requiring a gem that is not in your app's Gemfile.lock.
# It usually works. :)
#
# Example usage:
#
# Without BundlerBreakout:
#
# require 'mygem'
# LoadError: cannot load such file -- mygem
#
# With BundlerBreakout
# BundlerBreakout.require('mygem')
# defined?(Mygem)
# :constant
# 🎉

class BundlerBreakout
  def self.require(*)
    new(libname).load
  end

  def initialize(libname)
    @libname = libname
  end

  def load
    require @libname
  rescue LoadError
    $LOAD_PATH.unshift(*libs)
    require @libname
  end

  private

  def libs
    # Rather than fuss around with private API for Bundler/Gem, we can
    # shell out and see the effects on the $LOAD_PATH for requiring our
    # gem. Is it ugly? Yes. Does it work? Yeah...mostly :)
    clean_env do
      out = <<~`SH`
        ruby <<RUBY
          pre = \\$LOAD_PATH.dup
          require '#{@libname}'
          puts \\$LOAD_PATH - pre
        RUBY
      SH

      out.split("\n")
    end
  end

  def clean_env(&block)
    if defined?(Bundler)
      Bundler.with_clean_env(&block)
    else
      block.call
    end
  end
end