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💡 Lab 12 - Module boundaries

⏰ Estimated time: 10-15 minutes



📚 Learning outcomes:

  • Understand how to assign scopes and type tags to your libraries
  • How to specify boundaries around your tags and avoid circular dependencies in your repo
  • How to use linting to trigger warnings or errors when you are not respecting these boundaries


🏋️‍♀️ Steps :

  1. Open nx.json and finish tagging the apps accordingly:

    "projects": {
    "store": {
      "tags": ["scope:store", "type:app"]
    },
    .... <-- fill in the rest of the tags
  }



  2. Open the root .eslintrc.json, find the "@nrwl/nx/enforce-module-boundaries" rule and set the depConstraints:

    "depConstraints": [
    {
        "sourceTag": "scope:store",
        "onlyDependOnLibsWithTags": ["scope:store", "scope:shared"]
    },
    .... <-- finish adding constraints for the tags we defined in the previous step
]



  3. Run nx run-many --target=lint --all --parallel

    💡 nx run-many allows you run a specific target against a specific set of projects via the --projects=[..] option. However, you can also pass it the --all option to run that target against all projects in your workspace.

    💡 --parallel launches all the lint processes in parallel

  4. We talked about how importing a Feature lib should not be allowed from a UI lib. Let's test our lint rules by doing just that:

    • In libs/store/ui-shared/src/lib/store-ui-shared.module.ts
    • Try to import { StoreFeatureGameDetailModule } from '@bg-hoard/store/feature-game-detail';

  5. Run linting against all the projects again.

  6. You should see the expected error. Great! You can now delete the import above.

  7. We also talked about the importance of setting boundaries between your workspace scopes. Let's try and import a store lib from an api scope.

    • In apps/api/src/app/app.service.ts
    • Try to import { formatRating } from '@bg-hoard/store/util-formatters';

  8. Run linting on all projects - you should see another expected error.

  9. You can now delete the import above.

  10. Run linting again and check if all the errors went away.

    💡 Pass the suggested --only-failed option, so it doesn't relint everything.

  11. Commit everything before moving on to the next lab

🎓If you get stuck, check out the solution

➡️ Next lab ➡️