Hi there! We're thrilled that you'd like to contribute to this project. Your help is essential for keeping it great.

If you have any substantial changes that you would like to make, please open an issue first to discuss them with us.

Contributions to this project are released to the public under the project's open source license.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.

Adding a new component

Use the provided generator to create a component:

bundle exec thor component_generator my_component_name

To declare a dependency on an npm package, pass js to the generator:

bundle exec thor component_generator my_component_name --js=some-npm-package-name

Tag considerations

Components and slots should restrict which HTML tags they will render. For example, an Image component should never be rendered as an <h1>.

Consider which HTML tags make sense. Components typically fall under one of the following patterns:

1) Fixed tag that cannot be updated by the consumer:

system_arguments[:tag] = :h1

2) Allowed list of tags that are set with the tag: argument using the fetch_or_fallback helper.

system_arguments[:tag] = fetch_or_fallback(TAG_OPTIONS, tag, DEFAULT_TAG)


Before running the whole test suite with: script/test, you must run bundle exec rake docs:preview.

Run a subset of tests by supplying arguments to script/test:

  1. script/test FILE runs all tests in the file.
  2. script/test FILE:LINE runs test in specific line of the file.
  3. script/test 'GLOB' runs all tests for matching glob.
    • make sure to wrap the GLOB in single quotes ''.

System tests

Primer ViewComponents utilizes Cuprite for system testing components that rely on JavaScript functionality.

By default, the system tests run in a headless Chrome browser. Prefix the test command with HEADLESS=false to run the system tests in a normal browser.

Writing documentation

Documentation is written as YARD comments directly in the source code, compiled into Markdown via bundle exec rake docs:build and served by Doctocat.

Documentation / Demo Rails App

  • Docs: Generated YARD docs with examples, see components with usage instructions and examples
    • Typically runs on port 5400
    • To rebuild docs, run bundle exec rake docs:build
  • Demo App: See components on a plain page with no interfering framework or styling. Used to test functionality.
    • Typically runs on port 4000 - visit /rails/view_components/ in your browser
    • To rerender the templates, you do not have to restart the server. Run bundle exec rake docs:preview and refresh the page.

To run the documentation site and the demo app, run:


If you are running into issues or not seeing your updates, a few things you can try:

  • Delete the overmind.sock file and run script/dev again
  • Ensure you have run script/setup
  • Delete the node_modules directory and re-run script/setup
  • Run bundle exec rake docs:build
  • Run bundle exec rake docs:preview

Note: Overmind is required to run script/dev.

Developing with another app

In your Gemfile, change:

gem "primer_view_components"


gem "primer_view_components", path: "path_to_the_gem" # e.g. path: "~/primer/view_components"

Then, bundle install to update references. You'll now be able to see changes from the gem without having to build it. Remember that restarting the Rails server is necessary to see changes, as the gem is loaded at boot time.

To minimize the number of restarts, we recommend checking the component in Lookbook first, and then when it's in a good state, you can check it in your app.

Submitting a pull request

  1. Fork and clone the repository
  2. Configure and install the dependencies: ./script/setup
  3. Make sure the tests pass on your machine
  4. Create a new branch: git checkout -b my-branch-name
  5. Make your change, add tests, and make sure the tests still pass
  6. Add a changeset for your changes if needed
  7. Push to your fork and submit a pull request
  8. Pat yourself on the back and wait for your pull request to be reviewed and merged.

Here are a few things you can do that will increase the likelihood of your pull request being accepted:

  • Write tests.
  • Write YARD comments for component and slot initializers. Please document the purpose and general use of new components or slots you add, as well as the parameters they accept. See for example the comment style in app/components/primer/beta/counter.rb.
  • Add new components to the components list in Rakefile in the docs:build task, so that Markdown documentation is generated for them within docs/content/components/.
  • Keep your change as focused as possible. If there are multiple changes you would like to make that are not dependent upon each other, consider submitting them as separate pull requests.
  • Write a descriptive pull request message.

Deploying the Rails Lookbook

The Rails lookbook is currently deployed via GitHub Actions using this workflow. Deployments happen automatically on every merge to the main branch. The lookbook runs in a Kubernetes cluster hosted within our team's Azure subscription. Please contact a member of the team for access.

Publishing a Release

To publish a release, you must have an account on rubygems and npmjs. Additionally, you must have been added as a maintainer to the project. Please verify that you have 2FA enabled on both accounts.

  1. Once the changesets release PR has been approved and merged, run script/publish. This will build and publish the packages. You may be prompted to log into your rubygem and npm account.