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Simple and opinionated helper for creating Rubygem projects on GitHub



 Project Readme

Juwelier: Craft the perfect RubyGem for Ruby 2.3.x and Beyond

  • Intro
  • Migrating from Jeweler
  • Hot Ideas
    • Merging Jeweler and Juwelier
  • Hello, world
    • More juwelier options
  • Hello, rake tasks
    • Releasing
    • Version bumping
  • Customizing your gem
    • Project information
  • Juwelier Files
    • Dependencies
  • Juwelier Executables
    • Versioning
  • Juwelier Rake tasks
  • New Features
    • Rusty Gems Support
      • Example
  • Release Notes
  • Known Issues
  • Contributing to
  • Copyright


Provides the noble ruby developer with three primary features:

  • a library or managing and releasing RubyGem projects
  • a scaffold generator for starting new RubyGem projects
  • a means to write a RubyGem in Rust (creating a RustyGem)

PLEASE NOTE that I have taken over the original Jeweler and will be maintaining both repos for a while, and will eventually merge them to one. In the mean time, all new features shall be added to Juwelier, while keeping the origial Jeweler up-to-date with the latest Ruby releases. When the merge takes place, it will be in a manner that will not break either the Jeweler or the Juwelier camps.

“Juwelier” is pronounced “you-ve-LEER” (with German inflection! :))

Migrating from Jeweler

Note that if you have a preexisting project created with Jeweler, you may have some issues. Eventally I will provide a migration option, but in the meantime, you may wish to run this bash script from the root directory of your project:

for f in $(grep -irl jeweler *)
  sed -i 's/jeweler/juwelier/g' $f
  sed -i 's/Jeweler/Juwelier/g' $f
bundle update

Hot Ideas

Merging Jeweler and Juwelier

This just occured to me – we simply use metaprorgamming to use “Jeweler” or “Juwelier” in the generated code. All else would be the same. So the name of the script that ran would be captured and encoded by the script itself, and then used throughout the generation. That way, all can be happy.

Hello, world

Use RubyGems to install the heck out of juwelier to get started:

$ gem install juwelier

With juwelier installed, you can use the juwelier command to generate a new project. For the most basic use, just give it a name:

$ juwelier hello-gem

This requires some Git configuration (like name, email, GitHub account, etc), but juwelier will prompt along the way.

Your new hello-gem gem is ready in the hello-gem directory. Take a peek, and you’ll see several files and directories

  • Rakefile setup for juwelier, running tests, generating documentation, and releasing to
  • README.rdoc with contribution guidelines and copyright info crediting you
  • LICENSE with the MIT licensed crediting you
  • Gemfile with development dependencies filled in
  • lib/hello-gem.rb waiting for you to code
  • test/ containing a (failing) shoulda test suite shoulda

More juwelier options

The juwelier command supports a lot of options. Mostly, they are for generating baked in support for this test framework, or that.

Check out juwelier --help for the most up to date options.

Hello, rake tasks

Beyond just editing source code, you’ll be interacting with your gem using rake a lot. To see all the tasks available with a brief description, you can run:

$ rake -T

You’ll need a version before you can start installing your gem locally. The easiest way is with the version:write Rake task. Let’s imagine you start with 0.1.0

$ rake version:write MAJOR=0 MINOR=1 PATCH=0

You can now go forth and develop, now that there’s an initial version defined. Eventually, you should install and test the gem:

$ rake install

The install rake task builds the gem and =gem install=s it. You’re all set if you’re using RVM, but you may need to run it with sudo if you have a system-installed ruby:

$ sudo rake install


At last, it’s time to ship it! Make sure you have everything committed and pushed, then go wild:

$ rake release

This will automatically:

/Juwelier Generate hello-gem.gemspec and commit it / Use git to tag v0.1.0 and push it * Build hello-gem-0.1.0.gem and push it to

rake release accepts REMOTE(default: origin), LOCAL\_BRANCH(default: master), REMOTE\_BRANCH(default: master) and BRANCH(default: master)as options.

$ rake release REMOTE=upstream LOCAL_BRANCH=critical-security-fix REMOTE_BRANCH=v3

This will tag and push the commits on your local branch named critical-security-fix to branch named v3 in remote named upstream (if you have commit rights on upstream) and release the gem.

$ rake release BRANCH=v3

If both remote and local branches are the same, use BRANCH option to simplify. This will tag and push the commits on your local branch named v3 to branch named v3 in remote named origin (if you have commit rights on origin) and release the gem.

Version bumping

It feels good to release code. Do it, do it often. But before that, bump the version. Then release it. There’s a few ways to update the version:

# version:write like before
$ rake version:write MAJOR=0 MINOR=3 PATCH=0

# bump just major, ie 0.1.0 -> 1.0.0
$ rake version:bump:major

# bump just minor, ie 0.1.0 -> 0.2.0
$ rake version:bump:minor

# bump just patch, ie 0.1.0 -> 0.1.1
$ rake version:bump:patch

Then it’s the same release we used before:

$ rake release

Customizing your gem

If you’ve been following along so far, your gem is just a blank slate. You’re going to need to make it colorful and full of metadata.

You can customize your gem by updating your Rakefile. With a newly generated project, it will look something like this:

Juwelier require ‘juwelier’ do |gem| # gem is a Gem::Specification… see for more options = “whatwhatwhat” gem.summary = %Q{TODO: one-line summary of your gem} gem.description = %Q{TODO: longer description of your gem} = “” gem.homepage = “” Juwelier gem.authors = [“Joshua Nichols”] end JuwelierJuwelier

It’s crucial to understand the gem object is just a Gem::Specification. You can read up about it at This is the most basic way of specifying a gem, -managed or not. just exposes this to you, in addition to providing some reasonable defaults, which we’ll explore now.

Project information = "whatwhatwhat"

Every gem has a name. Among other things, the gem name is how you are able to gem install it. Reference

gem.summary = %Q{TODO: one-line summary of your gem}

This is a one line summary of your gem. This is displayed, for example, when you use gem list --details or view it on

gem.description = %Q{TODO: longer description of your gem}

Description is a longer description. Scholars ascertain that knowledge of where the description is used was lost centuries ago. = ""

This should be a way to get a hold of you regarding the gem.

gem.homepage = ""

The homepage should have more information about your gem. The juwelier generator guesses this based on the assumption your code lives on GitHub, using your Git configuration to find your GitHub username. This is displayed by gem list --details and on

gem.authors = ["Joshua Nichols"]

Hey, this is you, the author (or me in this case). The juwelier generator also guesses this from your Git configuration. This is displayed by gem list --details and on

Juwelier Files

ThJuweliere quickest way to add more files is to git add them. uses your Git repository to populate your gem’s files by including added and committed and excluding =.gitignore=d. In most cases, this is reasonable enough.

If you need to tweak the files, that’s cool. populates gem.files as a Rake::FileList. It’s like a normal array, except you can include and exclude file globs:

gem.files.exclude 'tmp' # exclude temporary directory
gem.files.include 'lib/foo/bar.rb' # explicitly include lib/foo/bar.rb

If that’s not enough, you can just set gem.files outright

gem.files = Dir.glob('lib/**/*.rb')


Dependencies let you define other gems that your gem needs to function. gem install your-gem will install your-gem’s dependencies along with it, and when you use your-gem in an application, the dependencies will be made available. Use gem.add_dependency to register them. Reference

gem.add_dependency 'nokogiri'

This will ensure a version of nokogiri is installed, but it doesn’t require anything more than that. You can provide extra args to be more specific:

gem.add_dependency 'nokogiri', '= 1.2.1' # exactly version 1.2.1
gem.add_dependency 'nokogiri', '>= 1.2.1' # greater than or equal to 1.2.1, ie, 1.2.1, 1.2.2, 1.3.0, 2.0.0, etc
gem.add_dependency 'nokogiri', '>= 1.2.1', '< 1.3.0' # greater than or equal to 1.2.1, but less than 1.3.0
gem.add_dependency 'nokogiri', '~> 1.2.1' # same thing, but more concise

When specifying which version is required, there’s a bit of the condunrum. You want to allow the most versions possible, but you want to be sure they are compatible. Using > 1.2.1= is fine most of the time, except until the point that 2.0.0 comes out and totally breaks backwards the API. That’s when it’s good to use ~> 1.2.1, which requires any version in the 1.2 family, starting with 1.2.1.

Juwelier Executables

Executables let your gem install shell commands. Just put any executable scripts in the bin/ directory, make sure they are added using git, and will take care of the rest.

When you need more finely grained control over it, you can set it yourself:

gem.executables = ['foo'] # note, it's the file name relative to `bin/`, not the project root


WeJuwelierJuwelier discussed earlier how to bump the version. The rake tasks are really just convience methods for manipulating the VERSION file. It just contains a version string, like 1.2.3.

VERSION is a convention used by , and is used to populate gem.version. You can actually set this yourself, and won’t try to override it:

gem.version = '1.2.3'

A common pattern is to have this in a version constant in your library. This is convenient, because users of the library can query the version they are using at runtime.

# in lib/foo/version.rb
class Foo
  module Version
    MAJOR = 1
    MINOR = 2
    PATCH = 3
    BUILD = 'pre3'

    STRING = [MAJOR, MINOR, PATCH, BUILD].compact.join('.')

# in Rakefile

Juwelier require ‘juwelier’ require ‘./lib/foo/version.rb’ do |gem| # snip gem.version = Foo::Version::STRING end

Juwelier Rake tasks

lives inside of Rake. As a result, they are dear friends. But, that friendship doesn’t interfere with typical Rake operations.

The Juwelier Rake means you can define your own namespaces, tasks, or use third party Rake libraries without cause for concern.

New Features

Rusty Gems Support

Beginning with version 2.4.0, we now have integration with Rust, so you are able to write Rust-enabled gems. Your users will have to have Rust installed on their systems, but this is easy to do.

This interface currently uses FFI, and I don’t have all the bugs worked out, so use at your own risk (for now).


The example code generated illustrates how to pass strings to Rust, and also how to pass data structures to Rust as JSON (highly recommended) and have it reformed into Rust structures in a typesafe manner.

First, create your Rusty Gem:

juwelier --semver --rusty foo

Next, cd into the foo directory and run bundle and attempt to run the test:

ruby lib/foo.rb

The test attempt should fail, since we have not built the Rust extension yet. Do so by doing the following:

cd rust
cd ..

And then attempt to run the test again:

ruby lib/foo.rb

That should work. Now install the gem locally with:

rake gemspec
rake install

And that should install your foo gem cleanly.

Release Notes

Version Date Notes
2.4.7 2017-06-24 Bundle update to allow the latest dependencies.
2.4.5 2017-05-14 Fixed Rusty interfacing example and the segfault it was generating.
2.4.0 2017-05-09 Support for Rusty Gems
2.3.5 2017-02-10 Revving Semver to be Semver2
2.2.3 2016-11-21 Psych bug fixed
2.2.2 2016-11-19 Added support for pry – includes pry, pry-byebug, pry-doc, pry-remote, pry-rescue. and pry-stack_explorer.
2.2.0 2016-11-19 Bugs with –semver fixed, new options for using .org and .markdown for README
2.1.3 2016-11-19 Problems with –semver, –required-version

Known Issues

Date Issue
2017-02-10 Orgmode and Markdown sync issue. They are out of sync for various reasons, and this must be ameorilated.
2016-11-19 On generation of the Markdown, the initial title does not linefeed before the header sequence.

Contributing to

  • Check out the latest master to make sure the feature hasn’t been implemented or the bug hasn’t been fixed yet
  • Ask on the mailing list for feedback on your proposal, to see if somebody else has done it.
  • Check out the issue tracker to make sure someone already hasn’t requested it and/or contributed it
  • Fork the project
  • Start a feature/bugfix branch
  • Commit and push until you are happy with your contribution
  • Make sure to add tests for the feature/bugfix. This is important so I don’t break it in a future version unintentionally.
  • Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate it to its own commit so I can cherry-pick around it.


Copyright (c) 2016 Fred Mitchell. See LICENSE for details.