Open Source ProjectsCode that Might be Useful to You

Talks I've GivenOn Technologies and Ideas

ThoughtsWhere I Sometimes Write Things

Resume If You Believe In Those

Follow Me On

GitHubIf coding is your thing

TwitterIf you tweet

Craft the perfect gem with Jeweler

I’ve been working on Jeweler for some time now, but never announced it officially. That changes now. This is kind of a long winded intro, so if you want to get to just jump into the action without the explanation, check out the latest README.


Rubygems are the awesome way of distributing your code to others. GitHub and git are the best tools for version control of your project. GitHub can even generate a Rubygem if you include a gemspec.

The trouble is when developing your Rubygems on GitHub, you generally do one of the following:

  • Manage the gemspec by hand
  • … why bother doing something by hand when you can automate it?
  • Write your own Rake stuff to create the Gem::Specification and output it to a gemspec file, and deal with keeping the Rakefile and gemspec in sync
  • … why keep reinventing the wheel for each project?
  • Use hoe or echoe for generating the gemspec
  • … why use tools made for the days before GitHub existed?
  • … why have extra stuff you aren’t going to use or want?
  • … what’s with the weird configuration that’s not particularly well documented except by example?

Jeweler was created with a few goals in mind:

  • Only use a Gem::Specification as configuration
  • Be one command away from version bumping and releasing
  • Store version information in one place
  • Only concern itself with git, gems, and versioning
  • Not be a requirement for using your Rakefile (you just wouldn’t be able to use its tasks)
  • Use Jeweler to manage Jeweler. Oh the meta!


Run the following if you haven’t already:

gem sources -a

Install the gem:

sudo gem install technicalpickles-jeweler

Configuration for an existing project

Armed with the gem, we can begin diving into an example. the-perfect-gem was setup as a simple example and showcase:

  require 'jeweler' do |s| = "jeweler"
    s.executables = "jeweler"
    s.summary = "Simple and opinionated helper for creating Rubygem projects on GitHub" = ""
    s.homepage = ""
    s.description = "Simple and opinionated helper for creating Rubygem projects on GitHub"
    s.authors = ["Josh Nichols"]
    s.files =  FileList["[A-Z]*", "{bin,generators,lib,test}/**/*", 'lib/jeweler/templates/.gitignore']
    s.add_dependency 'schacon-git'
rescue LoadError
  puts "Jeweler, or one of its dependencies, is not available. Install it with: sudo gem install technicalpickles-jeweler -s"

Here’s a rundown of what’s happening:

  • Wrap everything in a begin block, and rescue from LoadError
  • This lets us degrade gracefully if jeweler isn’t installed
  • Create an instance of Jeweler::Tasks
    • It gets yielded a new Gem::Specification
    • This is where all the configuration happens
    • Things you definitely need to specify:
      • name
    • Things you probably want to specify:
      • summary
      • email
      • homepage
      • description
      • authors
    • Things you can specify, but have defaults
    • files, defaults to FileList["[A-Z]*.*", "{bin,generators,lib,test,spec}/**/*"]
    • Things you shouldn’t specify:
    • version, because Jeweler takes care of this for you
    • Other things of interest
    • executables, if you have any scripts
    • add_dependency, if you have any dependencies
    • Keep in mind that this is a Gem::Specification, so you can do whatever you would need to do to get your gem in shape. See the reference for more details.

Bootstrap a new project

Before proceeding, take a minute to setup your git environment, specifically setup your name and email for git and your username and token for GitHub:

$ git config --global
$ git config --global 'John Doe'
$ git config --global github.user johndoe
$ git config --global github.token 55555555555555

Jeweler provides a generator, jeweler. It requires only one argument, the name of a repo you want to create. It also takes a few options:

  • shoulda: generate shoulda-based tests (this is the default)
  • bacon: generate bacon-based tests
  • –summary SUMMARY: specify the summary to use
  • –create-repo: create the repo on GitHub and enable rubygems for it

Putting it all together looks like:

$ jeweler --create-repo --summary "Oh so perfect" the-perfect-gem

The effect is this:

  • Creates the the-perfect-gem directory
  • Seeds it with some basic files:
  • .gitignore, with the usual suspects predefined
  • Rakefile, setup with tasks for jeweler, test, rdoc, and rcov
  • README, with your project name
  • LICENSE, MIT, with your name prefilled
  • test/test_helper, setup with shoulda, mocha, and a re-opened Test::Unit::TestCase
  • test/the_perfect_gem.rb, placeholder failing test
  • lib/the_perfect_gem.rb, placeholder library file
  • Initializes a git repository
  • Sets up as the origin git remote
  • Makes an initial commit
  • Creates up a new repository on GitHub and pushes to it (omit –create-repo to skip this)
  • Enables RubyGems for the repository

Overview of Jeweler workflow

Here’s the general idea:

  • Hack, commit, hack, commit, etc, etc
  • Version bump
  • Release
  • Have a delicious scotch

The hacking and the scotch are up to you, but Jeweler provides rake tasks for the rest.


Versioning information is stored in VERSION.yml. It’s a plain YAML file which contains three things:

  • major
  • minor
  • patch

Consider 1.5.3. This maps to:

  • major == 1
  • minor == 5
  • patch == 3
Your first time

When you first start using Jeweler, there won’t be a VERSION.yml, so it’ll assume 0.0.0.

If you need some arbitrary version, you can do one of the following:

  • rake version:write MAJOR=6 MINOR=0 PATCH=3
  • Write VERSION.yml by hand (lame)

After that

You have a few rake tasks for doing the version bump:

$ rake version:bump:patch # 1.5.1 -> 1.5.2
$ rake version:bump:minor # 1.5.1 -> 1.6.0
$ rake version:bump:major # 1.5.1 -> 2.0.0

If you need to do an arbitrary bump, use the same task you used to create VERSION.yml:

$ rake version:write MAJOR=6 MINOR=0 PATCH=3

The process of version bumping does a commit to your repo, so make sure your repo is in a clean state (ie nothing uncommitted).

Release it

It’s pretty straight forward:

$ rake release

This takes care of:

  • Generating a .gemspec for you project, with the version you just bumped to
  • Commit and push the updated .gemspec
  • Create a versioned tag
  • Push the tag

Play the waiting game

How do you know when your gem is built? Has My Gem Built Yet was specifically designed to answer that question.

If it happens to be down, you can also check out the GitHub Gem repo’s list. Just search for yourname-yourrepo.

Putting it all together

# hack, hack, hack, commit, etc
$ rake version:bump:patch release

Now browse to, and wait for it to be built.


You should have a good idea of what Jeweler is all about by now. It makes gem creation an impulse action. It makes managing versions of gems nice and automated.

Oh, and did I mention it is the GitHub recommended way for maintaining your gem?

Now go forth, and craft the perfect gem.

comments powered by Disqus