# require 'mspec/utils/ruby_name'
# require 'mspec/guards/guard'
# 
# # The ruby_exe helper provides a wrapper for invoking the
# # same Ruby interpreter as the one running the specs and
# # getting the output from running the code. If +code+ is a
# # file that exists, it will be run. Otherwise, +code+ should
# # be Ruby code that will be run with the -e command line
# # option. For example:
# #
# #   ruby_exe('path/to/some/file.rb')
# #
# # will be executed as
# #
# #   `#{RUBY_EXE} #{'path/to/some/file.rb'}`
# #
# # while
# #
# #   ruby_exe('puts "hello, world."')
# #
# # will be executed as
# #
# #   `#{RUBY_EXE} -e #{'puts "hello, world."'}`
# #
# # The ruby_exe helper also accepts an options hash with two
# # keys: :options and :args. For example:
# #
# #   ruby_exe('file.rb', :options => "-w", :args => "> file.txt")
# #
# # will be executed as
# #
# #   `#{RUBY_EXE} -w #{'file.rb'} > file.txt`
# #
# # If +nil+ is passed for the first argument, the command line
# # will be built only from the options hash.
# #
# # The RUBY_EXE constant can be set explicitly since the value
# # is used each time ruby_exe is invoked. The mspec runner script
# # will set ENV['RUBY_EXE'] to the name of the executable used
# # to invoke the mspec-run script. The value of RUBY_EXE will be
# # constructed as follows:
# #
# #   1. the value of ENV['RUBY_EXE']
# #   2. an explicit value based on RUBY_NAME
# #   3. cwd/(RUBY_NAME + $(EXEEXT) || $(exeext) || '')
# #   4. $(bindir)/$(RUBY_INSTALL_NAME)
# #
# # The value will only be used if the file exists and is executable.
# #
# # These 4 ways correspond to the following scenarios:
# #
# #   1. Using the MSpec runner scripts, the name of the
# #      executable is explicitly passed by ENV['RUBY_EXE']
# #      so there is no ambiguity.
# #
# #  Otherwise, if using RSpec (or something else)
# #
# #   2. Running the specs while developing an alternative
# #      Ruby implementation. This explicitly names the
# #      executable in the development directory based on
# #      the value of RUBY_NAME, which is probably initialized
# #      from the value of RUBY_ENGINE.
# #   3. Running the specs within the source directory for
# #      some implementation. (E.g. a local build directory.)
# #   4. Running the specs against some installed Ruby
# #      implementation.
# 
# class Object
#   def ruby_exe_options(option)
#     case option
#     when :env
#       ENV['RUBY_EXE']
#     when :engine
#       case RUBY_NAME
#       when 'rbx'
#         "bin/rbx"
#       when 'jruby'
#         "bin/jruby"
#       when 'ironruby'
#         "ir"
#       end
#     when :name
#       bin = RUBY_NAME + (Config::CONFIG['EXEEXT'] || Config::CONFIG['exeext'] || '')
#       File.join(".", bin)
#     when :install_name
#       bin = Config::CONFIG["RUBY_INSTALL_NAME"] || Config::CONFIG["ruby_install_name"]
#       bin << (Config::CONFIG['EXEEXT'] || Config::CONFIG['exeext'] || '')
#       File.join(Config::CONFIG['bindir'], bin)
#     end
#   end
# 
#   def resolve_ruby_exe
#     [:env, :engine, :name, :install_name].each do |option|
#       next unless cmd = ruby_exe_options(option)
#       exe = cmd.split.first
# 
#       # It has been reported that File.executable is not reliable
#       # on Windows platforms (see commit 56bc555c). So, we check the
#       # platform. 
#       if File.exists?(exe) and (SpecGuard.windows? or File.executable?(exe))
#         return cmd
#       end
#     end
#     nil
#   end
# 
#   def ruby_exe(code, opts = {})
#     body = code
#     working_dir = opts[:dir] || "."
#     Dir.chdir(working_dir) do
#       body = "-e #{code.inspect}" if code and not File.exists?(code)
#       cmd = [RUBY_EXE, ENV['RUBY_FLAGS'], opts[:options], body, opts[:args]]
#       `#{cmd.compact.join(' ')}`
#     end
#   end
# 
#   unless Object.const_defined?(:RUBY_EXE) and RUBY_EXE
#     require 'rbconfig'
# 
#     RUBY_EXE = resolve_ruby_exe or
#       raise Exception, "Unable to find a suitable ruby executable."
#   end
# end