Bundler Ruby Gem Development Tricks

Developing your own gem for your own application can be a pain– after you think you’re done with the gem, push it, and load it into your application, and there’s a defect, you need to go back to the gem, fix it, push it, and repeat. Or do you?

You don’t.

First:

There are some variations on this solution, but here’s my version.

In my $HOME/.bash_profile I add and source

export APP_GEMS_DIR=$HOME/workspace/gemsdev

(I also set it in my config/setup_load_paths.rb file that I use for passenger: ENV["APP_GEMS_DIR"] = File.expand_path("../../../", __FILE__))

Second:

In my Gemfile I add

if ENV['APP_GEMS_DIR']
  # for local gem development, use local gem directory so gem changes don't need to be pushed to test
  gem 'my_gem', :path => "#{ENV['APP_GEMS_DIR']}/my_gem", :require => "namespace/my_gem"
else
  gem 'my_gem', :require => "namespace/my_gem", :git => path_to_git_repo, :tag => tagname
end

As to why in the else clause I specified the repo and the tag, that is to allow parallel gem development. I could also set it to :branch => branchname, or :ref => ref_hash for using a consistant gem branch for release development or to freeze the gem at a know good revision. In fact, with this technique, you could, if you wanted, never bump the gem version again!

On benefit of this technique, is that when using the local gem, after you bundle install, you don’t have to keep do it again while you continue developing the gem.

To go back to non-gem-development mode, remove the lines you added from your bash_profile and setup_load_path.rb and unset $APP_GEMS_DIR

For an alternate way to manage gem development, see Andy Maleh’s post More Productive Rails Engine Development via Symlinking

UPDATE 2013-11-12

Rails engine example. With a folder in your Rails root called ‘tweet_engine’ that contains a Rails engine:

gem 'tweet_engine', path: 'tweet_engine'

You could even reference an external Gemfile like the devtools project does.

eval_gemfile 'shared/Gemfile'