A How-To Guide and Checklist for Releasing Crystal Shards
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💎 👩‍🏫 Crystal Shards 101

How to write and release Crystal Shards.

Build Status Docs GitHub release

What's a Shard?

Simply put, a Shard is a package of Crystal code, made to be shared-with and used-by other projects.


If you haven't already, install the latest version of the Crystal compiler. Installation instructions here


In this tutorial, we'll be making a Crystal library called palindrome-example.

For those who don't know, a palindrome is a word which is spelled the same way forwards as it is backwards. e.g. racecar, mom, dad, kayak, madam

Creating the Project

Begin by using the Crystal compiler to generate a new library in a subfolder of the current directory.

In your terminal, enter:

 $  crystal init lib palindrome-example
      create  palindrome-example/.gitignore
      create  palindrome-example/.editorconfig
      create  palindrome-example/LICENSE
      create  palindrome-example/README.md
      create  palindrome-example/.travis.yml
      create  palindrome-example/shard.yml
      create  palindrome-example/src/palindrome-example.cr
      create  palindrome-example/src/palindrome-example/version.cr
      create  palindrome-example/spec/spec_helper.cr
      create  palindrome-example/spec/palindrome-example_spec.cr
Initialized empty Git repository in /Users/YOUR_USER_NAME/.../palindrome-example/.git/

...and cd into the directory:

cd palindrome-example

Then add & commit to start tracking the files with Git:

 $  git add -A
 $  git commit -am "First Commit"
[master (root-commit) 77bad84] First Commit
 10 files changed, 102 insertions(+)
 create mode 100644 .editorconfig
 create mode 100644 .gitignore
 create mode 100644 .travis.yml
 create mode 100644 LICENSE
 create mode 100644 README.md
 create mode 100644 shard.yml
 create mode 100644 spec/palindrome-example_spec.cr
 create mode 100644 spec/spec_helper.cr
 create mode 100644 src/palindrome-example.cr
 create mode 100644 src/palindrome-example/version.cr

Writing the Code

The code you write is up to you, but how you write it impacts whether people want to use your library and/or help you maintain it.



Run crystal doc and open the files in /doc/ in your browser to see how your documentation is looking along the way. (the process of seeing your comments and code magically turned into documentation is surprisingly satisfying)

Coding Style

Writing a README

A good README can make or break your project. Awesome README is a nice curation of examples and resources on the topic.

Most importantly, your README should explain:

  1. what your library is
  2. what it does
  3. how to use it

This explanation should include a few examples along with subheadings.

NOTE: Be sure to replace all instances of [your-github-name] in the Crystal-generated README template with your Github username.

Fill out and insert the following block of markdown build badges below the description in your README.

The purpose of this is to inform users on the status of certain aspects of your repository. More on this in a minute.

[![Build Status](https://travis-ci.org/[YOUR-GITHUB-USERNAME]/[YOUR-REPOSITORY-NAME].svg?branch=master)](https://travis-ci.org/[YOUR-GITHUB-USERNAME]/[YOUR-REPOSITORY-NAME]) [![Docs](https://img.shields.io/badge/docs-available-brightgreen.svg)](https://[YOUR-GITHUB-USERNAME].github.io/[YOUR-REPOSITORY-NAME]/) [![GitHub release](https://img.shields.io/github/release/[YOUR-GITHUB-USERNAME]/[YOUR-REPOSITORY-NAME].svg)](https://github.com/[YOUR-GITHUB-USERNAME]/[YOUR-REPOSITORY-NAME]/releases)

Writing a shard.yml

The spec is your rulebook. Follow it.


Your shard.yml's name property should be concise and descriptive.


name: palindrome-example


Add a description to your shard.yml.

A description is a single line description used to search for and find your shard.

A description should be:

  1. Informative
  2. Discoverable


It's hard for anyone to use your project if they can't find it. crystalshards.xyz is currently the go-to place for Crystal libraries, so that's what we'll optimize for.

There are people looking for the exact functionality of our library and the general functionality of our library. e.g. Bob needs a palindrome library, but Felipe is just looking for libraries involving text and Susan is looking for libraries involving spelling.

Our name is already descriptive enough for Bob's search of "palindrome". We don't need to repeat the palindrome keyword. Instead, we'll catch Susan's search for "spelling" and Felipe's search for "text".

description: |
  A textual algorithm to tell if a word is spelled the same way forwards as it is backwards.


  • Create a repository with the same name and description as specified in your shard.yml.

  • Add and commit everything:

$ git add -A && git commit -am "shard complete"
  • Add the remote:
$ git remote add public https://github.com/[YOUR-GITHUB-NAME]/[YOUR-REPOSITORY-NAME].git
  • Push it:
$ git push public master

Github Releases

It's good practice to do Github Releases.

Start by navigating to your repository's releases page.

Click "Create a new release".

According to the Crystal Shards README,

When libraries are installed from Git repositories, the repository is expected to have version tags following a semver-like format, prefixed with a v. Examples: v1.2.3, v2.0.0-rc1 or v2017.04.1

Accordingly, in the input that says tag version, type v0.1.0. Make sure this matches the version in shard.yml. Title it v0.1.0 and write a short description for the release.

Click "Publish release" and you're done!

You'll now notice that the Github Release badge has updated in your README.

Follow Semantic Versioning and create a new release every time your push to master.

Setting up Travis CI and .travis.yml

If you haven't already, sign up for Travis CI.

Add the following lines to your .travis.yml:

  - crystal spec

This tells Travis CI to run your tests.

Commit and push to Github.

Follow these guidelines to get your repo up & running on Travis CI.

Once you're up and running, and the build is passing, the Build badge will update in your README.

Hosting your docs on Github-Pages

Add the following script to your .travis.yml:

  - crystal docs

This tells Travis CI to generate your documentation.

Next, add the following lines to your .travis.yml.

  provider: pages
  skip_cleanup: true
  github_token: $GITHUB_TOKEN
    branch: master
  local_dir: doc

Set the Environment Variable, GITHUB_TOKEN, with your personal access token.

If you've been following along, your .travis.yml file should look something like this:

language: crystal
  - crystal spec
  - crystal docs
  provider: pages
  skip_cleanup: true
  github_token: $GITHUB_TOKEN
    branch: master
  local_dir: doc

Click Here for the official documentation on deploying to GH-Pages with Travis CI.


  1. Fork it ( https://github.com/mccallofthewild/crystal-shards-101/fork )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request