Ruby on Rails 3 - Reload lib directory for each request

Question

I'm creating a new engine for a rails 3 application. As you can guess, this engine is in the lib directory of my application.

However, i have some problems developing it. Indeed, I need to restart my server each time I change something in the engine.

Is there a way to avoid this ?

Can I force rails to completely reload the lib directory or a specific file and his requirements for each request ?

Thanks for your help :)

Answer 1

I couldn't get any of the above to work for me so I dug in the Rails code a bit and came up with this:

New file: config/initializers/reload_lib.rb

if Rails.env == "development"
  lib_reloader = ActiveSupport::FileUpdateChecker.new(Dir["lib/**/*"]) do
    Rails.application.reload_routes! # or do something better here
  end

  # For Rails 5.1+
  ActiveSupport::Reloader.to_prepare do
    lib_reloader.execute_if_updated
  end

  # For Rails pre-5.1 
  ActionDispatch::Callbacks.to_prepare do
    lib_reloader.execute_if_updated
  end

end

Yes, I know it's disgusting but it's a hack. There might be a better way to trigger a full reload, but this works for me. My specific use case was a Rack app mounted to a Rails route so I needed it to reload as I worked on it in development.

Basically what it does is it checks if any files in /lib have changed (modified timestamp) since last loaded and then triggers a reload if they change.

I might also mention I have this in my config/application.rb

config.autoload_paths += %W(#{config.root}/lib)
config.autoload_paths += Dir["#{config.root}/lib/**/"]

Which just by default makes sure everything in my lib directory gets loaded.

Yays!

Answer 2

TL;DR

• put this in config/application.rb

  config.eager_load_paths += ["#{Rails.root}/lib"]

• remove require statements for your lib files

Go!

---

Let me explain in detail.

I don't know why this answer is accepted, since it doesn't help with reloading lib folder on each request. First I thought that it works for Rails 2, but the question clearly states that it was for Rails 3 and the release date of 3.0.0 is before the date of the answer.

Other answers seem over-complicated or don't provide a real solution.

I decided to investigate things a little, because it was bothering me and I've even found out that people have a workaround for this and it involves saving lib files inside app/models in development and then moving it to /lib when done. We can do better, right?

---

My solution is tested against:

• Rails 3.0.20
• Rails 3.1.12
• Rails 3.2.13
• Rails 4.0.0.rc1

Put this into your config/application.rb:

# in config/application.rb
config.eager_load_paths += ["#{Rails.root}/lib"]

That's it!™

Make sure you put it here since it will not work if you put it in config/environments/development.rb, for example.

Make sure your remove all the require statements for your /lib code since require statements will also cause this solution to not work.

---

This code implicitly requires your code, so if you do environment checks (which are unnecessary) and instead of the above code, you decide to write something like this:

# in config/application.rb
config.eager_load_paths += ["#{Rails.root}/lib"] if Rails.env.development?

you should watch out on the old require statements, since they are still required on all the non-development environments, in this scenario.

So if you still decide to do environment checks, make sure you do inverse checks for require statements. Otherwise you'll get bitten!

require "beer_creator" unless Rails.env.development?

You might think that writing entire paragraph about something that's unnecessary is also unnecessary, but I think that warning people about something that's necessary when doing something unnecessary is also necessary.

If you would like to know more about this topic, check out this little tutorial.