rubocop-view_component

A RuboCop extension that encourages ViewComponent best practices.

Installation

Add to your Gemfile:

gem 'rubocop-view_component', require: false

Add to your .rubocop.yml:

require:
  - rubocop-view_component

Cops

This gem provides several cops to enforce ViewComponent best practices:

  • ViewComponent/ComponentSuffix - Enforce -Component suffix for ViewComponent classes
  • ViewComponent/NoGlobalState - Prevent direct access to params, request, session, etc.
  • ViewComponent/PreferPrivateMethods - Suggest making helper methods private (analyzes ERB templates to avoid flagging methods used in views)
  • ViewComponent/PreferSlots - Detect HTML parameters that should be slots
  • ViewComponent/PreferComposition - Avoid inheriting one ViewComponent from another (prefer composition)
  • ViewComponent/TestRenderedOutput - Encourage testing rendered output over private methods
  • ViewComponent/MissingPreview - Ensure every ViewComponent has a corresponding preview file (requires PreviewPaths configuration)

Optional Configuration

Base Class

By default, the cops detect classes that inherit from ViewComponent::Base or ApplicationComponent. If your project uses a different base class (e.g. Primer::Component), you can configure additional parent classes under AllCops, for example:

# .rubocop.yml
AllCops:
  ViewComponentParentClasses:
    - MyApp::BaseComponent

No Super

View Component convention is to not calling super in component initializers, but that may cause Lint/MissingSuper failures from RuboCop. We suggest disabling that rule for your view components directory, for example:

# .rubocop.yml
Lint/MissingSuper:
  Exclude:
    - 'app/components/**/*'

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

To release a new version:

  1. Update the version number in lib/rubocop/view_component/version.rb
  2. Run bundle install to update Gemfile.lock
  3. Commit and push both files
  4. Trigger the Push Gem workflow via GitHub Actions (uses trusted publishing — no API key needed)

Real-World Verification

The cops are tested against real-world component libraries as baselines to catch regressions.

The script/verify script downloads component libraries (cached in verification/), runs all ViewComponent cops against them, and compares the results to checked-in snapshots. This runs automatically in CI.

Primer ViewComponents

To verify against primer/view_components locally:

script/verify primer

If you intentionally change cop behavior, regenerate the snapshot:

script/verify primer --regenerate

To force download the latest Primer source:

script/verify primer --update

x-govuk Components

To verify against x-govuk/govuk-components locally:

script/verify govuk

If you intentionally change cop behavior, regenerate the snapshot:

script/verify govuk --regenerate

To force download the latest x-govuk source:

script/verify govuk --update

Polaris ViewComponents

To verify against baoagency/polaris_view_components locally:

script/verify polaris

If you intentionally change cop behavior, regenerate the snapshot:

script/verify polaris --regenerate

To force download the latest Polaris source:

script/verify polaris --update

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/andyw8/rubocop-view_component.

License

The gem is available as open source under the terms of the MIT License.