rubocop-view_component

A RuboCop extension that encourages ViewComponent best practices.

Add to your Gemfile:

gem 'rubocop-view_component', require: false

Add to your .rubocop.yml:

plugins:
  - rubocop-view_component

Note: From v0.7.0 onwards, this gem makes use of rubydex to discover which classes inherit from ViewComponent::Base. UseProjectIndex is required. Without it, cops that depend on ancestry detection will raise an error.

AllCops:
  UseProjectIndex: true

If you use a ViewComponent library such as primer then you'll also need to set ProjectIndexIncludesGems: true so the cops can resolve ancestry chains that pass through gem classes.

For more background on how RuboCop uses rubydex for cross-file analysis, see RuboCop 1.89: Project-Wide Analysis with Rubydex.

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 (defaults to test/components/previews and spec/components/previews if PreviewPaths is not configured). Abstract base classes with descendants are automatically exempt.

Several cops (ComponentSuffix, PreferComposition, TestRenderedOutput) default to running only on files under app/components/. If your project uses a different path, override Include in your .rubocop.yml:

# .rubocop.yml
ViewComponent/ComponentSuffix:
  Include:
    - 'app/components/**/*.rb'
    - 'engines/*/app/components/**/*.rb'

ViewComponent convention is to not call 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/**/*'

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)

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.

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

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

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

To verify against substancelab/flowbite-components locally:

script/verify flowbite

If you intentionally change cop behavior, regenerate the snapshot:

script/verify flowbite --regenerate

To force download the latest Flowbite source:

script/verify flowbite --update

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

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