fix: replace deprecated/removed functions in eslint-plugin-next

[z0n]

Hi everyone, this is my first PR to such a large project so please be gentle. 😄 I'm also new to publishing packages so I'm not sure if I'm missing any steps.

ESLint 9.0.0 came out a few days ago and unfortunately, eslint-plugin-next is not compatible as it uses deprecated (and with ESLint 9.0.0 removed) functions.
In this PR, I replaced the deprecated functions with the suggested replacements (check this out).

Regarding backwards compatibility, everything I used is available since ESLint 8.40 (released May 2023). I'm not sure how far back Next.js support goes but it feels fine to me.

I successfully tested some rules locally with ESLint 9.0.0 and this eslint.config.js (flat config format):

import js from '@eslint/js';
import nextPlugin from '@next/eslint-plugin-next';
import prettierRecommended from 'eslint-plugin-prettier/recommended';
import importSortPlugin from 'eslint-plugin-simple-import-sort';
import globals from 'globals';
import tseslint from 'typescript-eslint';

/**
 * TypeScript config with strict type checking and no type checking for JS files.
 */
const typeScriptConfig = [
  ...tseslint.configs.strictTypeChecked,
  {
    plugins: {
      '@typescript-eslint': tseslint.plugin,
    },
    languageOptions: {
      parser: tseslint.parser,
      parserOptions: {
        project: true,
      },
    },
  },
  {
    // disable type-aware linting on JS files
    files: ['**/*.js', '**/*.mjs', '**/*.cjs'],
    ...tseslint.configs.disableTypeChecked,
  },
];

/**
 * Next.js config with recommended and core web vitals rules.
 */
const nextConfig = {
  plugins: {
    '@next/next': nextPlugin,
  },
  rules: {
    ...nextPlugin.configs.recommended.rules,
    ...nextPlugin.configs['core-web-vitals'].rules,
  },
};

/**
 * Import sort config with simple-import-sort plugin.
 */
const importSortConfig = {
  plugins: {
    'simple-import-sort': importSortPlugin,
  },
  rules: {
    'simple-import-sort/imports': 'error',
    'simple-import-sort/exports': 'error',
  },
};

/**
 * The final ESLint config wrapped with the tseslint.config helper for type hinting.
 */
export default tseslint.config(
  {
    ignores: ['.next', '.yarn', '**/*.d.ts', 'node_modules'],
  },
  {
    languageOptions: {
      globals: {
        ...globals.browser,
        ...globals.node,
      },
    },
  },
  js.configs.recommended,
  ...typeScriptConfig,
  nextConfig,
  prettierRecommended,
  importSortConfig,
);

It has a few more configs but I'm sure you can remove most of them. The important one is the nextConfig. Also important: Run eslint and not next lint, it's currently not compatible with the new flat config format.

Related discussion: #54238

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[r34son]

@z0n Hi! Here is another migration guide https://eslint.org/docs/latest/extend/plugin-migration-flat-config
Looks like you're missing a bunch of things to migrate to v9

[z0n]

@r34son This was meant as a first step, I know there's a few more things to do. This will make the eslint-plugin-next work for now. This PR doesn't include the whole flat config migration 🙂

[henrikvtcodes]

Is there any progress on this so far? If work still needs to be done I could jump on it.

[z0n]

@henrikvtcodes I'm still available but I need some feedback here. 😕

For full ESLint 9 support we also need the stuff @r34son mentioned but I didn't feel confident enough to update the whole plugin system. 😄

This PR makes eslint-plugin-next work with ESLint 9 though so I think it can stand on its own.

[ijjk]

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[ijjk]

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General

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build cache Overall increase ⚠️

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