Docs/examples suggestion for forbidding feature folder dependencies

[jzaefferer]

Summary

Thank you for this great tool! It took me a while to build two specific rules, and since I had to look through issues to find an answer, I figured my solution could be useful for others. Specifically I wanted rules that a src/feature folder can only depend on itself or on modules outside of src/features (but not one feature to another). And except two specific modules, no module is allowed to depend on any src/feature folder.

Context

The context is a React app with a src/App.tsx that does a lot of imports from folders in src/features/ folders. The App is allowed to import these features, but nothing else should like (src/components). And each feature should be standalone, and only depend on shared components (e.g. src/components).

I eventually managed to put these rules together:

forbidden: {
    {
      name: 'not-into-features',
      comment:
        'Code outside of features should not depend on features, except App and Shell',
      severity: 'error',
      from: { pathNot: ['^src/features', '^src/App', '^src/Shell'] },
      to: { path: '^src/features' },
    },
    {
      name: 'features-not-to-features',
      comment:
        'One feature should not depend on another feature (in a separate folder)',
      severity: 'error',
      from: { path: '(^src/features/)([^/]+)/' },
      to: { path: '^$1', pathNot: '$1$2' },
    },
}

Example violations:

error not-into-features: src/hooks/useSearchBar.ts → src/features/LibraryPage/buildUrl.ts
error features-not-to-features: src/features/user-profile/components/UserProfile.jsx → src/features/ChangeAvatarModal/ChangeAvatarModalContent.jsx

The first rule was relatively easy, but the 2nd rule was rather difficult to write, and I only managed after reading #330 (comment)

Maybe these could be useful examples for others, e.g. on https://github.com/sverweij/dependency-cruiser/blob/develop/doc/rules-tutorial.md where its going to be easier to find than in issues.

[sverweij]

Hi @jzaefferer

I've been toying with expanding the documentation in this respect (looking for inspiration to http-proxy-middleware's 'recipes'), but was doubting it'd actually fill a need - as as an author it's one of my blind spots. This is why your feedback is very valuable. Thank you!

I'll expand the documentation with a bunch of examples/ recipes, starting with yours!