.eslintrc.js

module.exports = {
  // Dep names: 'eslint-plugin-jest', 'eslint-plugin-react', 'eslint-plugin-react-hooks', 'eslint-plugin-import', '@typescript-eslint/eslint-plugin', '@typescript-eslint/parser', 'eslint-plugin-jsx-a11y', '@babel/eslint-parser'

  // REVIEW: React plugins and rules
  // REVIEW: TypeScript rules/config (file extensions, plugins, parsers, etc.)
  // REVIEW: Make sure all extensions to be linted (other than .js) are covered at some point in the overrides section. This allows ESLint to lint them without passing in the --ext CLI option. @see https://github.com/eslint/rfcs/pull/20/files?short_path=89f153b#diff-89f153b40e57baa60c4da2693bb17305
  // REVIEW: jsx-a11y

  plugins: ["react-hooks", "import", "jsx-a11y"],
  // jsx-a11y: could remove usage, or even move to "plugin:jsx-a11y/strict"
  extends: ["plugin:react/recommended", "plugin:jsx-a11y/recommended"],
  env: {
    es6: true,
    node: true,
  },
  // REVIEW: Remove this if not using babel
  parser: "@babel/eslint-parser",
  parserOptions: {
    // REVIEW: Depending on the browsers supported for the project, this might need to go down. Safari and non-Chromium Edge seem to be the biggest ones to hold things back, but the things they don't support from 2016 onwards are rarely used. Also, this probably isn't necessary if using Babel
    // @see https://kangax.github.io/compat-table/es2016plus/
    ecmaVersion: 2020,
    sourceType: "module",
  },
  settings: {
    react: {
      version: "detect",
    },
  },
  // REVIEW: May need to add things based on the project
  ignorePatterns: ["dist/", "build/", "coverage/"],

  rules: {
    /**
     * Possible Errors
     *
     * https://eslint.org/docs/rules/#possible-errors
     */
    "no-compare-neg-zero": 2,
    "no-cond-assign": 2,
    "no-console": [2, { allow: ["error"] }],
    "no-constant-condition": 2,
    "no-debugger": 2,
    "no-dupe-args": 2,
    "no-dupe-keys": 2,
    "no-duplicate-case": 2,
    "no-empty": [2, { allowEmptyCatch: true }],
    "no-empty-character-class": 2,
    "no-ex-assign": 2,
    "no-extra-boolean-cast": 2,
    "no-func-assign": 2,
    "no-inner-declarations": 2,
    "no-invalid-regexp": 2,
    "no-irregular-whitespace": 2,
    "no-obj-calls": 2,
    "no-regex-spaces": 2,
    "no-sparse-arrays": 0,
    "no-template-curly-in-string": 2,
    "no-unexpected-multiline": 2,
    "no-unreachable": 2,
    "no-unsafe-finally": 2,
    "use-isnan": 2,
    "valid-typeof": 2,
    eqeqeq: ["error", "always", { null: "ignore" }],

    /**
     * Best Practices
     *
     * https://eslint.org/docs/rules/#best-practices
     */
    "prefer-regex-literals": 2,
    "no-caller": 2,
    "no-case-declarations": 2,
    "no-empty-pattern": 2,
    "no-extend-native": 2,
    "no-new-wrappers": 2,
    "no-octal": 2,
    "no-redeclare": 2,
    "no-self-assign": 2,
    "no-unused-labels": 2,
    "no-var": 2,

    /**
     * ESLint's "Variables" rules
     *
     * https://eslint.org/docs/rules/#variables
     */
    "no-delete-var": 2,
    "no-undef": 2,
    "no-unused-vars": [
      2,
      {
        args: "none",
        ignoreRestSiblings: true,
      },
    ],
    "no-use-before-define": [
      2,
      {
        functions: false,
      },
    ],

    /**
     * ECMAScript 6
     *
     * https://eslint.org/docs/rules/#ecmascript-6
     */
    "constructor-super": 2,

    /**
     * React
     */
    // REVIEW: Depends on the project (TS, if you care about prop-types, etc.)
    "react/prop-types": 0,

    /**
     * React hooks
     */
    "react-hooks/rules-of-hooks": 2,
    "react-hooks/exhaustive-deps": 2,

    /**
     * eslint-plugin-import
     */
    // REVIEW: Check to see if the team is OK with this
    "import/no-default-export": 2,
  },
  overrides: [
    /**
     * Files only ran in the browser. Modify this to point at the client/src directory, depending on the project
     */
    {
      files: ["client/**/*+(js|jsx|ts|tsx)"],
      env: {
        jest: true,
        node: false,
        browser: true,
      },
    },

    /**
     * Test files. Node is enabled, since Jest inherently is ran through Node. Browser is enabled because of the simulated browser env that Jest runs tests in.
     */
    {
      // REVIEW: Jest setup file, test utils, etc. Anything that's not a `spec` file that should be treated in the test env
      files: [
        "client/**/*.spec.@(js|jsx|ts|tsx)",
        "./jest.setup.js",
        "client/test-utils/**/*.(js|jsx|ts|tsx)",
      ],
      plugins: ["jest"],
      env: {
        jest: true,
        node: true,
        browser: true,
      },
      rules: {
        "jest/no-disabled-tests": 2,
        "jest/no-commented-out-tests": 2,
        "jest/no-focused-tests": 2,
        "jest/no-identical-title": 2,
        "jest/no-jasmine-globals": 2,
        "jest/no-jest-import": 2,
        "jest/no-mocks-import": 2,
        "jest/no-standalone-expect": 2,
        "jest/no-test-callback": 2,
        "jest/no-test-prefixes": 2,
        "jest/no-try-expect": 2,
        "jest/prefer-to-be-null": 2,
        "jest/prefer-to-be-undefined": 2,
        "jest/prefer-to-contain": 2,
        "jest/prefer-to-have-length": 2,
        "jest/prefer-todo": 2,
        "jest/valid-describe": 2,
        "jest/valid-expect-in-promise": 2,
        "jest/valid-expect": 2,
      },
    },

    /**
     * TypeScript files.
     */
    {
      files: ["**/*.@(ts|tsx)"],
      parser: "@typescript-eslint/parser",
      parserOptions: {
        project: "./tsconfig.json",
      },
      plugins: ["@typescript-eslint"],
      rules: {
        // Turn off rules that TypeScript's compiler can/will catch on its own. This is necessary, since this project has a mix of JS and TS files.
        // REVIEW: Make sure the TS compiler enforces these rules on its own before committing to turning these ESLint rules off
        "no-unused-vars": 0,
        "no-use-before-define": 0,
        "no-undef": 0,

        // `@typescript-eslint` rules. The default recommended rules are a bit picky, and included useless warnings instead of error. So we explicitly choose the ones that could actually help catch bugs, reasonably enforce consistency, or reasonably enforce modern TS
        "@typescript-eslint/await-thenable": 2,
        "@typescript-eslint/ban-types": 2,
        "@typescript-eslint/consistent-type-assertions": 2,
        "@typescript-eslint/no-explicit-any": 2,
        "@typescript-eslint/no-for-in-array": 2,
        "@typescript-eslint/no-inferrable-types": 2,
        "@typescript-eslint/no-misused-new": 2,
        "@typescript-eslint/no-misused-promises": 2,
        "@typescript-eslint/no-namespace": 2,
        "@typescript-eslint/no-this-alias": 2,
        "@typescript-eslint/no-unnecessary-type-assertion": 2,
        "@typescript-eslint/no-var-requires": 2,
        "@typescript-eslint/prefer-includes": 2,
        "@typescript-eslint/prefer-namespace-keyword": 2,
        "@typescript-eslint/prefer-string-starts-ends-with": 2,
        "@typescript-eslint/triple-slash-reference": 2,
        "@typescript-eslint/unbound-method": 2,
        "@typescript-eslint/no-array-constructor": 2,
        "@typescript-eslint/require-await": 2,
      },
    },
  ],
}