index.js

import jest from "eslint-plugin-jest";
import js from "@eslint/js";
import import_ from "eslint-plugin-import";
import stylistic from "@stylistic/eslint-plugin";
import ts from 'typescript-eslint';
import globals from 'globals';

export default [
  js.configs.recommended,
  { ignores: ["**/node_modules/"] }, {
    languageOptions: {
      globals: {...globals.node},
      ecmaVersion: 11,
      sourceType: "commonjs",
      parserOptions: {
        ecmaFeatures: {
          globalReturn: true,
        },
      },
    },
    settings: {jest: {version: 29}},
    plugins: {
      import: import_,
      "@stylistic": stylistic,
    },
    rules: {
      "no-console": "off",

      // bad code, modern (new code patterns we don't like because they're less readable or performant)
      "no-restricted-globals": ["error", "Proxy", "Reflect", "WeakSet"],

      // bad code, deprecated (deprecated/bad patterns that should be written a different way)
      "eqeqeq": "error",
      "func-names": "off", // has minor advantages but way too verbose, hurting readability
      "guard-for-in": "off", // guarding is a deprecated pattern, we just use no-extend-native instead
      "init-declarations": "off", // TypeScript lets us delay initialization safely
      "no-caller": "error",
      "no-eval": "error",
      "no-extend-native": "error",
      "no-implied-eval": "error",
      "no-inner-declarations": ["error", "functions"],
      "no-iterator": "error",
      "no-labels": ["error", {allowLoop: true, allowSwitch: true}],
      "no-multi-str": "error",
      "no-new-func": "error",
      "no-new-wrappers": "error",
      "no-proto": "error",
      "no-restricted-syntax": ["error", "WithStatement"],
      "no-sparse-arrays": "error",
      "no-var": "error",
      "no-with": "error",

      // probably bugs (code with no reason to exist, probably typos)
      "array-callback-return": "error",
      "block-scoped-var": "error", // not actually used; precluded by no-var
      "callback-return": [2, ["callback", "cb", "done"]],
      "consistent-this": "off", // we use arrow functions instead
      "constructor-super": "error",
      "default-case": "off", // hopefully TypeScript will let us skip `default` for things that are exhaustive
      "no-case-declarations": "off", // meh, we have no-shadow
      "no-duplicate-case": "error",
      "no-empty": ["error", {allowEmptyCatch: true}],
      "no-extra-bind": "error",
      "no-extra-label": "error",
      "no-fallthrough": "error",
      "no-label-var": "error",
      "no-new-require": "error",
      "no-new": "error",
      "no-redeclare": "off", // Useful with type namespaces
      "no-self-compare": "error",
      "no-sequences": "error",
      "no-shadow-restricted-names": "error",
      "no-shadow": "error",
      "no-template-curly-in-string": "error",
      "no-throw-literal": "error",
      "no-undef": ["error", {typeof: true}],
      "no-unmodified-loop-condition": "error",
      "no-unused-expressions": "error",
      "no-unsafe-finally": "error",
      "no-unused-labels": "error",
      "no-use-before-define": ["error", {functions: false, classes: false, variables: false}],
      "use-isnan": "error",
      "valid-typeof": "error",

      // style choices
      "no-constant-condition": ["error", {checkLoops: false}],
      "no-lonely-if": "off",
      "radix": ["error", "as-needed"],

      // naming style
      "camelcase": "off", // mostly only so we can import `child_process`
      "id-length": "off",
      "id-match": "off",
      "new-cap": ["error", {newIsCap: true, capIsNew: false}],
      "no-underscore-dangle": "off",

      // syntax style (local syntactical, usually autofixable formatting decisions)

      "@stylistic/arrow-parens": "off",
      "arrow-body-style": "error",
      "@stylistic/brace-style": ["error", "1tbs", {allowSingleLine: true}],
      "@stylistic/comma-dangle": ["error", {
        arrays: "always-multiline",
        objects: "always-multiline",
        imports: "always-multiline",
        exports: "always-multiline",
        tuples: "always-multiline",
        functions: "ignore",
      }],
      "@stylistic/comma-style": ["error", "last"],
      "curly": ["error", "multi-line", "consistent"],
      "dot-notation": "off",
      "max-len": ["error", {code: 100, ignoreUrls: true}],
      "@stylistic/new-parens": "error",
      "no-array-constructor": "error",
      "no-div-regex": "error",
      "no-duplicate-imports": "error",
      "no-extra-parens": "off",
      "@stylistic/no-floating-decimal": "error",
      "no-mixed-requires": "error",
      "@stylistic/no-multi-spaces": "error",
      "no-new-object": "error",
      "no-octal-escape": "error",
      "no-return-assign": ["error", "except-parens"],
      "no-undef-init": "off",
      "no-unneeded-ternary": "error",
      "no-useless-call": "error",
      "no-useless-computed-key": "error",
      "no-useless-concat": "off",
      "no-useless-rename": "error",
      "object-shorthand": ["error", "methods"],
      "one-var": "off",
      "operator-assignment": "off",
      "prefer-arrow-callback": "off",
      "prefer-const": ["error", {destructuring: "all"}],
      "quote-props": "off",
      "quotes": "off",
      "semi": ["error", "always"],
      "sort-vars": "off",
      "vars-on-top": "off",
      "@stylistic/wrap-iife": ["error", "inside"],
      "@stylistic/wrap-regex": "off",
      "yoda": ["error", "never", {exceptRange: true}],

      // whitespace
      "@stylistic/array-bracket-spacing": ["error", "never"],
      "@stylistic/arrow-spacing": ["error", {before: true, after: true}],
      "@stylistic/block-spacing": ["error", "always"],
      "@stylistic/comma-spacing": ["error", {before: false, after: true}],
      "@stylistic/computed-property-spacing": ["error", "never"],
      "@stylistic/dot-location": ["error", "property"],
      "@stylistic/eol-last": ["error", "always"],
      "@stylistic/func-call-spacing": "error",
      "@stylistic/function-paren-newline": ["error", "consistent"],
      "@stylistic/indent": ["error", 2, {flatTernaryExpressions: true, SwitchCase: 1}],
      "@stylistic/key-spacing": "error",
      "@stylistic/keyword-spacing": ["error", {before: true, after: true}],
      "@stylistic/lines-around-comment": "off",
      "@stylistic/no-mixed-spaces-and-tabs": "error",
      "@stylistic/no-multiple-empty-lines": ["error", {max: 1}],
      "@stylistic/no-trailing-spaces": ["error", {ignoreComments: false}],
      "@stylistic/object-curly-spacing": ["error", "never"],
      "@stylistic/operator-linebreak": ["error", "after", {overrides: {"?": "before", ":": "before"}}],
      "@stylistic/padded-blocks": ["error", "never"],
      "@stylistic/padding-line-between-statements": "off",
      "@stylistic/rest-spread-spacing": ["error", "never"],
      "@stylistic/semi-spacing": ["error", {before: false, after: true}],
      "@stylistic/space-before-blocks": ["error", "always"],
      "@stylistic/space-before-function-paren": ["error", {anonymous: "always", named: "never"}],
      "@stylistic/spaced-comment": ["error", "always", {exceptions: ["*"]}],
      "@stylistic/space-in-parens": ["error", "never"],
      "@stylistic/space-infix-ops": "error",
      "@stylistic/space-unary-ops": ["error", {words: true, nonwords: false}],
      "@stylistic/template-curly-spacing": ["error", "never"],

        // imports
      "import/order": ["error", {
        "newlines-between": "always",
        "alphabetize": {
          order: "asc",
          caseInsensitive: true,
        },
      }],
      "sort-imports": ["error", {
        ignoreDeclarationSort: true,
        allowSeparatedGroups: true,
      }],
    },
  },
  ...ts.config({
    files: ["**/*.ts", "**/*.tsx"],
    plugins: {'@typescript-eslint': ts.plugin},
    extends: [
      js.configs.recommended,
      ...ts.configs.recommended,
      ...ts.configs.recommendedTypeChecked,
    ],
    languageOptions: {
      parser: ts.parser,
      ecmaVersion: 11,
      sourceType: "module",
      parserOptions: {
        tsconfigRootDir: ".",
        project: ["./tsconfig.json"],
        warnOnUnsupportedTypeScriptVersion: false,
      },
    },
    rules: {
      // TODO revisit
      "@typescript-eslint/explicit-function-return-type": "off",
      "@typescript-eslint/member-ordering": "off",
      // "@typescript-eslint/no-extraneous-class": "error",
      // "@typescript-eslint/no-type-alias": "error",

      "@typescript-eslint/no-namespace": "off",
      "@stylistic/new-parens": "off",// used for the `new class {...}` pattern
      "no-prototype-builtins": "off",

      // typescript-eslint defaults too strict
      "@typescript-eslint/ban-ts-comment": "off",
      "@typescript-eslint/no-empty-function": "off",
      "@typescript-eslint/no-explicit-any": "off",
      "@typescript-eslint/no-unsafe-argument": "off",
      "@typescript-eslint/no-non-null-assertion": "off",
      "@typescript-eslint/no-use-before-define": ["error", {functions: false, classes: false, variables: false}],
      "@typescript-eslint/unbound-method": ["error", {ignoreStatic: true}],
      // disable additional typescript-eslint 3.0 defaults
      "@typescript-eslint/explicit-module-boundary-types": "off",
      "@typescript-eslint/no-unsafe-member-access": "off",
      "@typescript-eslint/no-unsafe-assignment": "off",
      "@typescript-eslint/no-unsafe-call": "off",
      "@typescript-eslint/no-unsafe-return": "off",

      // probably bugs
      "@typescript-eslint/no-dupe-class-members": "error",
      "@typescript-eslint/no-empty-interface": "error",
      "@typescript-eslint/no-extra-non-null-assertion": "error",
      "@typescript-eslint/no-misused-new": "error",
      "@typescript-eslint/no-non-null-asserted-optional-chain": "error",
      "@typescript-eslint/return-await": ["error", "in-try-catch"],
      "no-dupe-class-members": "off",
      "no-unused-expressions": ["error", {allowTernary: true}], // ternary is used to convert callbacks to Promises

      // naming style
      "@typescript-eslint/camelcase": "off",

      // syntax style (local syntactical, usually autofixable formatting decisions)
      "@typescript-eslint/adjacent-overload-signatures": "error",
      // "@typescript-eslint/array-type": "error",
      "@typescript-eslint/consistent-type-assertions": ["error", {assertionStyle: "as"}],
      "@typescript-eslint/consistent-type-definitions": ["error", "interface"],
      "@typescript-eslint/explicit-member-accessibility": ["error", {accessibility: "no-public"}],
      "@stylistic/member-delimiter-style": "error",
      "@typescript-eslint/parameter-properties": "error",
      "@typescript-eslint/no-this-alias": "error",
      "@typescript-eslint/no-var-requires": "error",
      "@typescript-eslint/prefer-as-const": "error",
      "@typescript-eslint/prefer-for-of": "error",
      "@typescript-eslint/prefer-function-type": "error",
      "@typescript-eslint/prefer-includes": "error",
      "@typescript-eslint/prefer-namespace-keyword": "error",
      "prefer-object-spread": "error",
      "@typescript-eslint/prefer-optional-chain": "error",
      "@typescript-eslint/triple-slash-reference": "error",
      "@typescript-eslint/unified-signatures": "error",

      "quotes": "off",
      "@stylistic/quotes": ["error", "single", {avoidEscape: true}],
      "semi": "off",
      "@stylistic/semi": ["error", "always"],

      // whitespace
      "@stylistic/type-annotation-spacing": "error",
      "@stylistic/spaced-comment": ["error", "always", {exceptions: ["*", "/"]}],

      // overriding base
      "no-use-before-define": "off",
      "no-shadow": "off",
      "@typescript-eslint/no-shadow": ["error"],
      // BUG: conflicts with @stylistic/object-curly-spacing in TypeScript types
      "@stylistic/block-spacing": "off",

      // types
      "@typescript-eslint/restrict-plus-operands": "off",
      "@typescript-eslint/prefer-string-starts-ends-with": "off",
      // "@typescript-eslint/switch-exhaustiveness-check": "error",

      // types - probably bugs
      "@typescript-eslint/no-floating-promises": ["error", {ignoreVoid: false, ignoreIIFE: true}],
      "@typescript-eslint/no-for-in-array": "error",
      "@typescript-eslint/no-misused-promises": "error",
      "@typescript-eslint/only-throw-error": "error",

      // syntax style (local syntactical, usually autofixable formatting decisions)
      "@typescript-eslint/no-unnecessary-qualifier": "off",
      "@typescript-eslint/no-unnecessary-type-arguments": "error",
      "@typescript-eslint/no-unnecessary-type-assertion": "error",
      "@typescript-eslint/prefer-regexp-exec": "error",
    },
  }),
  {
    files: ["**/*.test.js", "**/tests/*.js"],
    ...jest.configs['flat/recommended'],
    plugins: {jest},
    languageOptions: {globals: {...jest.environments.globals.globals}},
    rules: {
      ...jest.configs['flat/recommended'].rules,
      ...jest.configs['flat/style'].rules,
    },
  },
  {
    files: ["**/*.test.ts", "**/tests/*.ts"],
    ...jest.configs['flat/recommended'],
    plugins: {jest},
    languageOptions: {globals: {...jest.environments.globals.globals}},
    rules: {
      ...jest.configs['flat/recommended'].rules,
      ...jest.configs['flat/style'].rules,
      "@typescript-eslint/unbound-method": "off",
      "jest/unbound-method": "error",
    },
  },
];