.eslintrc.js

module.exports = {
  root: true,
  env: { node: true },
  parser: '@typescript-eslint/parser',
  plugins: [ '@typescript-eslint' ],
  ignorePatterns: '.eslintrc.js',
  extends: [
    'eslint:recommended',
    'plugin:@typescript-eslint/recommended',
    'plugin:@typescript-eslint/recommended-requiring-type-checking'
  ],
  rules: {
    // I let the compiler infer the return types of methods, functions... itself.
    // For my use, I do not need a stable interface for outside modules, because I am
    // the only one to consume my own code. It is another story if you build a library with a stable interface.
    '@typescript-eslint/explicit-module-boundary-types': 'off',

    // The 'any' type should be used with caution.
    // Still, I sometime use it for ugly legacy code or well scoped area.
    // PS: a better alternative would be the `unknown` type and turn the rule on again.
    '@typescript-eslint/no-explicit-any': 'off',

    // I use async on all funcions handled by fastify for now. I have to check before changing this.
    '@typescript-eslint/require-await': 'off',

    // Used to notify typescript that request.session is not nil when we know it isn't.
    '@typescript-eslint/no-non-null-assertion': 'off'

    // Feel free to enable/disable some rules depending on your needs.
  }
}