Question

I’m currently developing a framework that basically executes another application, e.g. rails within the context of another ruby program. My initial attempt was simply to boot the app like this:

def load_app!

  # Load the rails application
  require './config/application'

  # Initialize the rails application
  @app = App::Application.initialize!

end

Problem here, is that the framework’s requires conflict with the loaded application so the initialize! call never works although it would in a normal ruby program.

So my question is, if anyone knows a method to basically scope this calls into a unit that behaves like a blank RVM environment. So basically a behavior like this:

require 'json'
puts JSON.generate({:name => "test"})

blank_environment do
  puts JSON.generate({:name => "test"})
  #=> uninitialized constant JSON

  require 'json'
  puts JSON.generate({:name => "test"})
end

It’s not done with undefining or unloading the currently loaded constants because I don’t know all of them because I’m using gems that have other dependencies again.

So is there a cool way? Or any other way to handle this?

UPDATE:

Just came across an idea. Why is ruby’s require method always requiring for the global scope? Wouldn’t it be a very nice feature to actually scope the loaded modules under the the current module?

module ScopeA
  require 'json' #> adds support for ScopeA::JSON  

  # due to normal ruby scoping everything can be called like normal in here
  JSON.parse("something")
end

# JSON should not be available here

module ScopeB
  require 'yaml'

  YAML.parse("something") # but no JSON, of course
end

Doesn’t something like this exist? include already has to know the constants…

Thanks in advance!

Answer 1

Well, after some more research it really doesn’t seem possible the way I need it.

I now implemented a basic version using distributed ruby, which doesn’t quite satisfy me:

require 'drb/drb'

URI = "druby://localhost:8787"

# Blank environment
pid = fork do
  Signal.trap("INT") { puts "Stopping Server.."; exit }

  class Application
    def call(env)
      [200,{},""]
    end
  end

  DRb.start_service(URI, Application.new)
  DRb.thread.join
end

# Working environment
DRb.start_service

app = DRbObject.new_with_uri(URI)
puts app.call({})

Process.kill("INT", pid)
Process.wait

If anyone comes up with a better approach, it’s highly appreciated!