Migrate to Nx monorepo with create-eslint-config package

[hanna-skryl]

Closes #46

Summary

• Convert repository to Nx monorepo with two packages: @code-pushup/eslint-config (existing) and @code-pushup/create-eslint-config (new, coming soon)
• Configure Nx to orchestrate tasks (test, lint, typecheck, build, docs) with caching
• Replace release-it with Nx releases
• Update CI pipeline to use nx affected for checking affected projects
• Set up Commitlint and Commitizen for conventional commit enforcement
• Add monorepo documentation (root README, CONTRIBUTING.md)

Note

The npx nx g @nx/workspace:convert-to-monorepo generator did not produce a usable result for this repository (mangled package name, incomplete file movement, nested scope directory). The monorepo structure was created manually instead.

[matejchalk]

The rule doesn't catch errors for the eslint-config project. You can test this by removing one of the peer dependencies (e.g., globals) from its package.json.

After some digging, I found that @nx/dependency-checks skips everything if it can't find a build target.

https://github.com/nrwl/nx/blob/44abcb2ab49e102885d7eef2231b80024364158f/packages/eslint-plugin/src/rules/dependency-checks.ts#L152-L154

This can be resolved by adding our typecheck target. However, Nx defaults to {projectRoot]/**/* when the target has no cache inputs.

https://github.com/nrwl/nx/blob/44abcb2ab49e102885d7eef2231b80024364158f/packages/js/src/utils/find-npm-dependencies.ts#L101-L103

So it checks imports in non-production code and reports them as missing (vitest, build-md, @typescript-eslint/utils, compare-versions). This may be resolved by excluding certain file patterns.

Finally, Nx thinks eslint-import-resolver-typescript isn't a valid peer dependency because it can't see it being imported. This is a false positive that we need to exclude.

This is the configuration I ended up with in packages/eslint-config/eslint.config.js:

{
  files: ['**/package.json'],
  languageOptions: { parser: jsoncParser },
  rules: {
    '@nx/dependency-checks': [
      'error',
      {
        buildTargets: ['typecheck'],
        ignoredFiles: [
          '{projectRoot}/scripts/**',
          '{projectRoot}/tests/**',
          '{projectRoot}/vitest.config.js',
          '{projectRoot}/eslint.config.js',
        ],
        ignoredDependencies: ['eslint-import-resolver-typescript'],
      },
    ],
  },
},

There might be a more elegant workaround than using the typecheck build target. If we set it to some target that already uses the production cache inputs, our non-production file patterns could be defined in one place. Maybe something like typecheck:prod? 🤔

[hanna-skryl]

I applied your suggestion, keeping the explicit ignoredFiles so the intent is visible at the rule definition. I also added a short comment for extra clarity.