.eslintrc.js

const rules = {
  // This is a useless warning, as mount hooks require empty arrays
  // and sometimes you just don't need to track all dependencies.
  "react-hooks/exhaustive-deps": 0,

  // Disabled in favor of TS definitions.
  "react/prop-types": 0,

  "react/no-unescaped-entities": 0,

  "no-empty": [
    2,
    {
      allowEmptyCatch: true,
    },
  ],

  // Turn this off in favor of unused-imports plugin.
  "no-unused-vars": 0,

  // Warn on unused imports.
  // Note that this is upgraded to an error during git commits.
  "unused-imports/no-unused-imports": 1,

  // Turn this off in favor of simple-import-sort rule.
  "sort-imports": 0,

  "simple-import-sort/sort": [
    1,
    {
      // Custom groupings based on documentation from
      // https://www.npmjs.com/package/eslint-plugin-simple-import-sort#custom-grouping
      groups: [
        // Side effect imports
        ["^\\u0000"],
        // External packages: things that start with a letter, digit, underscore, or @
        ["^@?\\w"],
        // Local packages: things that start with @client
        ["^@client", "^@shared", "^@server"],
        // Absolute/other imports: anything that does not start with a dot
        ["^[^.]"],
        // Relative imports: anything that starts with a dot
        ["^\\."],
      ],
    },
  ],

  // 'debugger' statements are only warnings because we want to allow them during local development
  // Note that this is upgraded to an error during git commits.
  "no-debugger": 1,

  /** We warn about this to make you aware that require() is not recommended, but sometimes
   * needed. You should eslint-ignore any valid usages. */
  "@typescript-eslint/no-var-requires": 1,

  // The TS compiler will already error if it can't detect the return type from the code.
  // Forcing the return type is just too noisy sometimes.
  "@typescript-eslint/explicit-function-return-type": 0,

  // This is up for debate. We currently use a lot of I-prefixes so it's disabled for now.
  // https://github.com/microsoft/TypeScript-Handbook/issues/121
  "@typescript-eslint/interface-name-prefix": 0,

  // Many of our API endpoints use snake_case.
  "@typescript-eslint/camelcase": 0,

  // This rule is too restrictive. Try not to use `any` if it's avoidable, but sometimes it's
  // necessary.
  "@typescript-eslint/no-explicit-any": 0,

  // Unused vars are warnings during local development.
  // Disables eslint rule in favor of typescript-specific rule below.
  // Note that this is upgraded to an error during git commits.
  "unused-imports/no-unused-vars": 0,
  "@typescript-eslint/no-unused-vars": 1,

  "@typescript-eslint/no-use-before-define": 0,

  "prettier/prettier": 1,
};

module.exports = {
  extends: ["eslint:recommended", "plugin:react/recommended", "plugin:prettier/recommended"],
  env: {
    es6: true,
    browser: true,
    node: true,
  },
  parserOptions: {
    ecmaVersion: 9,
  },
  rules,
  plugins: ["simple-import-sort", "unused-imports"],
  overrides: [
    {
      files: "{client,server}/src/**/*.{ts,tsx}",
      parser: "@typescript-eslint/parser",
      plugins: ["@typescript-eslint"],
      extends: [
        "eslint:recommended",
        "plugin:react/recommended",
        "plugin:prettier/recommended",
        "plugin:@typescript-eslint/eslint-recommended",
        "plugin:@typescript-eslint/recommended",
      ],
      rules,
    },
  ],
};