Calling a different rbenv ruby using backticks from a rake task running via rbenv errors

[theirishpenguin]

Overview

Given we have ruby and 2.2.2 and jruby-9.0.0.0 both installed via rbenv
When we call a rake task using RBENV_VERSION=2.2.2
And that rake task calls a jruby script using backticks
Then we get the error...

Could not find rake-10.4.2 in any of the sources
Run `bundle install` to install missing gems.

Example app

Example rails app at https://github.com/theirishpenguin/rails_app_calling_jruby_script which features an example task that showcases this ( https://github.com/theirishpenguin/rails_app_calling_jruby_script/blob/master/lib/tasks/demo_task.rake)

Steps to reproduce using demo app

• Install ruby 2.2.2 and 2.2.2 and jruby-9.0.0.0 using rbenv
• git clone git@github.com:theirishpenguin/rails_app_calling_jruby_script.git
• cd rails_app_calling_jruby_script
• RBENV_VERSION=2.2.2 bundle install
• RBENV_VERSION=2.2.2 bundle exec rake demo_task:demo
• We get the error

Now try without rbenv when calling the rake task

... # Ensure you are still in the rails_app_calling_jruby_script directory

• bundle install
• bundle exec rake demo_task:demo
• We get the success message "*** GOT HERE ***"

Also

• I've tried a few variants on invoking the script (with rbenv init calls that mimic the .bashrc sourcing) but to no avail
• I was thinking it might be possible to clear/replace some of the ENV variables temporarily before shelling out to the jruby script and then restore them afterwards but I don't understand this well enough to be sure it would work

[theirishpenguin]

If, just prior to shelling out to jruby, you delete some env variables as follows...

ENV.delete("GEM_HOME")                                                      
ENV.delete("GEM_PATH")                                                      
ENV.delete 'BUNDLE_BIN_PATH'                                                
ENV.delete 'BUNDLE_GEMFILE'                                                 
ENV.delete 'RUBYOPT'

... and modify the RBENV_VERSION to point at jruby...

ENV['RBENV_VERSION'] = 'jruby-9.0.0.0'

... and modify ENV["RUBYLIB"] and ENV['PATH'] to be the same as your jruby environment then we can reach the success message.

Will look into how to replace this ENV variables temporarily in order to launch the jruby subscript.

[theirishpenguin]

Finally, a working solution. Here is an example rake task where the environment will be jruby-based within the with_jruby_env block...

require 'active_record'                                                         

namespace :foo do                                                        
  desc 'Invokes bar based on the current RAILS_ENV.'          
  task :bar => :environment do                                        

    with_jruby_env('jruby-9.0.0.0') do                                          
      puts `jruby -S ./my_jruby_script.rb`
    end                                                                         

  end                                                                           

  # Thanks to the this article for all the env switching foo :-)                
  # https://www.fedux.org/articles/2015/07/22/using-env-in-mri-ruby-and-jruby.html
  def with_jruby_env(jruby_version, &block)                                     
    old_env = ENV.to_hash                                                       

    # Delete undesired variables                                                
    ENV.delete 'GEM_HOME'                                                      
    ENV.delete 'GEM_PATH'                                                      
    ENV.delete 'BUNDLE_BIN_PATH'                                                
    ENV.delete 'BUNDLE_GEMFILE'                                                 
    ENV.delete 'RUBYOPT'                                                        

    # Update incorrect variables                                                
    ENV['RBENV_VERSION'] = jruby_version                                        
    ENV["RUBYLIB"] = "#{ENV['HOME']}/.rbenv/rbenv.d/exec/gem-rehash:"              

    # Change path to use jruby                                                  
    ENV['PATH'] = "#{ENV['HOME']}/.rbenv/versions/#{ENV['RBENV_VERSION']}/bin/:" +
      ENV['PATH'].split(':').reject{|dir| dir.include? '.rbenv/versions'}.join(':')

    block.call if block_given?                                                  
  ensure                                                                        
    ENV.clear                                                                   
    ENV.update old_env                                                          
  end                                                                           

end

[mislav]

Thanks for sharing the solution. This is a known problem. Please see #121