feat(eslint-plugin-next): add pageExtensions option

[nnmax]

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What?

This PR is to fix a problem where @next/next/no-html-link-for-pages doesn't work when pageExtensions are configured.

As to why a new option should be provided, see the commend.

How?

An ESLint option called pageExtensions is provided.

Options Type

The rule accepts the following options:

type NoHTMLLinkForPagesOptions =
  | string
  | string[]
  | {
      pagesDir?: string | string[]
      pageExtensions?: string | string[]
    }

The values can be:

• string - It's equivalent to the pagesDir argument.
• string[] - It's equivalent to the pagesDir argument.
• An object with the following properties:
  • pagesDir - a path to a directory or an array of paths to directories
  • pageExtensions - a string or an array of strings representing the extensions of the page files

Usage

If you set the pageExtensions config, this rule will not work and the pageExtensions option must be set for it to work.

// next.config.js
/** @type {import('next').NextConfig} */
module.exports = {
  pageExtensions: ['page.tsx', 'mdx'],
}

// .eslintrc.js
module.exports = {
  rules: {
    '@next/next/no-html-link-for-pages': [
      'error',
      { pageExtensions: ['page.tsx', 'mdx'] },
    ],
  },
}
}

fix vercel#53473