eslint.config.js

import url from "node:url";
import eslintPluginJs from "@eslint/js";
import eslintPluginStylisticJs from "@stylistic/eslint-plugin-js";
import eslintPluginTypescriptEslint from "@typescript-eslint/eslint-plugin";
import { isCI } from "ci-info";
import eslintConfigPrettier from "eslint-config-prettier";
import eslintPluginJest from "eslint-plugin-jest";
import eslintPluginN from "eslint-plugin-n";
import eslintPluginReact from "eslint-plugin-react";
import eslintPluginRegexp from "eslint-plugin-regexp";
import eslintPluginSimpleImportSort from "eslint-plugin-simple-import-sort";
import eslintPluginUnicorn from "eslint-plugin-unicorn";
import globals from "globals";
import eslintPluginPrettierInternalRules from "./scripts/tools/eslint-plugin-prettier-internal-rules/index.js";

const toPath = (file) => url.fileURLToPath(new URL(file, import.meta.url));

const ignores = `
.tmp
test*.*
# Ignore directories and files in 'tests/format'
tests/format/**/*
# Unignore directories and 'jsfmt.spec.js', 'format.test.js' file
!tests/format/**/
!tests/format/**/format.test.js
# TODO: Remove this in 2025, somehow '!tests/format/**/jsfmt.spec.js' does not work
!tests/format/**/jsfmt.*.js
tests/integration/cli/
scripts/release/node_modules
coverage/
dist*/
**/node_modules/**
website/build/
website/static/playground.js
website/static/lib/
scripts/benchmark/*/
**/.yarn/**
**/.pnp.*
`
  .split("\n")
  .filter((pattern) => pattern && !pattern.startsWith("#"));

export default [
  eslintPluginJs.configs.recommended,
  eslintPluginRegexp.configs["flat/recommended"],
  eslintPluginUnicorn.configs["flat/recommended"],
  eslintConfigPrettier,
  {
    languageOptions: {
      globals: { ...globals.builtin, ...globals.node },
    },
    plugins: {
      "@stylistic/js": eslintPluginStylisticJs,
      "@typescript-eslint": eslintPluginTypescriptEslint,
      n: eslintPluginN,
      "prettier-internal-rules": eslintPluginPrettierInternalRules,
      "simple-import-sort": eslintPluginSimpleImportSort,
    },

    rules: {
      "arrow-body-style": ["error", "as-needed"],
      curly: "error",
      "dot-notation": "error",
      eqeqeq: "error",
      "logical-assignment-operators": "error",
      "no-console": isCI ? "error" : "warn",
      "no-constant-binary-expression": "error",
      "no-duplicate-imports": "error",
      "no-else-return": [
        "error",
        {
          allowElseIf: false,
        },
      ],
      "no-implicit-coercion": "error",
      "no-inner-declarations": "error",
      "no-lonely-if": "error",
      "no-unneeded-ternary": "error",
      "no-useless-return": "error",
      "no-unused-expressions": [
        "error",
        {
          allowShortCircuit: true,
          allowTernary: true,
        },
      ],
      "no-unused-vars": [
        "error",
        {
          ignoreRestSiblings: true,
        },
      ],
      "no-var": "error",
      "object-shorthand": [
        "error",
        "always",
        {
          avoidExplicitReturnArrows: true,
        },
      ],
      "one-var": ["error", "never"],
      "prefer-arrow-callback": "error",
      "prefer-const": [
        "error",
        {
          destructuring: "all",
        },
      ],
      "prefer-destructuring": [
        "error",
        {
          VariableDeclarator: {
            array: false,
            object: true,
          },
          AssignmentExpression: {
            array: false,
            object: false,
          },
        },
        {
          enforceForRenamedProperties: false,
        },
      ],
      "prefer-object-has-own": "error",
      "prefer-object-spread": "error",
      "prefer-rest-params": "error",
      "prefer-spread": "error",
      "require-await": "error",
      "require-unicode-regexp": "error",
      "symbol-description": "error",
      yoda: [
        "error",
        "never",
        {
          exceptRange: true,
        },
      ],

      // Internal rules
      "prettier-internal-rules/jsx-identifier-case": "error",
      "prettier-internal-rules/massage-ast-parameter-names": "error",
      "prettier-internal-rules/no-identifier-n": "error",
      "prettier-internal-rules/prefer-fs-promises-submodule": "error",

      /* @stylistic/eslint-plugin-js */
      "@stylistic/js/quotes": [
        "error",
        "double",
        {
          avoidEscape: true,
        },
      ],

      /* @typescript-eslint/eslint-plugin */
      "@typescript-eslint/prefer-ts-expect-error": "error",

      /* eslint-plugin-n */
      "n/no-path-concat": "error",

      /* eslint-plugin-regexp */
      "regexp/match-any": [
        "error",
        {
          allows: ["dotAll"],
        },
      ],
      /* cspell:disable-next-line */
      "regexp/no-extra-lookaround-assertions": "error",
      "regexp/no-missing-g-flag": "error",
      "regexp/no-useless-flag": [
        "error",
        {
          strictTypes: false,
        },
      ],
      /* cspell:disable-next-line */
      "regexp/prefer-lookaround": [
        "error",
        {
          strictTypes: false,
        },
      ],
      "regexp/no-super-linear-backtracking": "off",
      "regexp/unicode-property": [
        "error",
        {
          generalCategory: "never",
          key: "long",
          property: {
            binary: "long",
            generalCategory: "long",
            script: "long",
          },
        },
      ],

      /* eslint-plugin-simple-import-sort */
      "simple-import-sort/imports": [
        "error",
        {
          groups: [
            // https://github.com/lydell/eslint-plugin-simple-import-sort/blob/20e25f3b83c713825f96b8494e2091e6600954d6/src/imports.js#L5-L19
            // Side effect imports.
            [String.raw`^\u0000`],
            // Remove blank lines between groups
            // https://github.com/lydell/eslint-plugin-simple-import-sort#how-do-i-remove-all-blank-lines-between-imports
            [
              // Node.js builtins prefixed with `node:`.
              "^node:",
              // Packages.
              // Things that start with a letter (or digit or underscore), or `@` followed by a letter.
              String.raw`^@?\w`,
              // Absolute imports and other imports such as Vue-style `@/foo`.
              // Anything not matched in another group.
              "^",
              // Relative imports.
              // Anything that starts with a dot.
              String.raw`^\.`,
            ],
          ],
        },
      ],
      "simple-import-sort/exports": "error",

      /* eslint-plugin-unicorn */
      "unicorn/escape-case": "off",
      "unicorn/catch-error-name": "off",
      "unicorn/consistent-destructuring": "off",
      "unicorn/consistent-function-scoping": "off",
      "unicorn/import-style": "off",
      "unicorn/no-array-callback-reference": "off",
      "unicorn/no-array-method-this-argument": "off",
      "unicorn/no-array-reduce": "off",
      "unicorn/no-await-expression-member": "off",
      "unicorn/no-for-loop": "off",
      "unicorn/no-hex-escape": "off",
      "unicorn/no-negated-condition": "off",
      "unicorn/no-nested-ternary": "off",
      "unicorn/no-null": "off",
      "unicorn/no-process-exit": "off",
      "unicorn/no-thenable": "off",
      "unicorn/no-unreadable-array-destructuring": "off",
      "unicorn/no-useless-switch-case": "off",
      "unicorn/no-useless-undefined": [
        "error",
        {
          checkArrowFunctionBody: false,
        },
      ],
      "unicorn/number-literal-case": "off",
      "unicorn/numeric-separators-style": "off",
      "unicorn/prefer-array-flat": [
        "error",
        {
          functions: ["flat", "flatten"],
        },
      ],
      "unicorn/prefer-add-event-listener": "off",
      "unicorn/prefer-at": [
        "error",
        {
          getLastElementFunctions: ["getLast"],
        },
      ],
      "unicorn/prefer-code-point": "off",
      "unicorn/prefer-dom-node-append": "off",
      "unicorn/prefer-dom-node-remove": "off",
      "unicorn/prefer-export-from": [
        "error",
        {
          ignoreUsedVariables: true,
        },
      ],
      "unicorn/prefer-global-this": "off",
      "unicorn/prefer-query-selector": "off",
      "unicorn/prefer-ternary": "off",
      "unicorn/prevent-abbreviations": "off",
      "unicorn/relative-url-style": "off",
      "unicorn/switch-case-braces": ["error", "avoid"],
      "unicorn/template-indent": "error",
    },

    linterOptions: {
      reportUnusedDisableDirectives: "error",
    },
  },
  {
    ignores,
  },
  // CommonJS modules
  {
    files: [
      "**/*.cjs",
      "scripts/tools/eslint-plugin-prettier-internal-rules/**/*.js",
      "website/**/*.js",
    ],
    languageOptions: {
      sourceType: "script",
    },
    rules: {
      strict: ["error", "global"],
      "unicorn/prefer-module": "off",
      "unicorn/prefer-node-protocol": "off",
    },
  },
  {
    files: ["scripts/**/*", "tests/config/install-prettier.js"],
    rules: {
      "no-console": "off",
    },
  },
  {
    files: ["scripts/**/*.js"],
    rules: {
      "unicorn/prefer-top-level-await": "error",
    },
  },
  {
    files: [
      "tests/config/**/*.js",
      "tests/format/**/format.test.js",
      "tests/integration/**/*.js",
      "tests/unit/**/*.js",
      "tests/dts/unit/**/*.js",
      "scripts/release/__tests__/**/*.spec.js",
    ],
    plugins: { jest: eslintPluginJest },
    languageOptions: {
      globals: eslintPluginJest.environments.globals.globals,
    },
    rules: {
      "@stylistic/js/quotes": [
        "error",
        "double",
        {
          avoidEscape: true,
          allowTemplateLiterals: true,
        },
      ],
      "jest/valid-expect": [
        "error",
        {
          alwaysAwait: true,
        },
      ],
      "jest/prefer-to-be": "error",
    },
  },
  {
    files: ["tests/format/**/*.js"],
    rules: {
      "prettier-internal-rules/no-legacy-format-test": "error",
    },
  },
  {
    files: ["tests/integration/**/*.js"],
    rules: {
      "prettier-internal-rules/await-cli-tests": "error",
    },
  },
  {
    files: ["tests/**/*.js"],
    rules: {
      // TODO: Enable this when we drop support for Node.js v14
      "logical-assignment-operators": "off",
      "unicorn/prefer-array-flat": "off",
      "unicorn/prefer-array-flat-map": "off",
      "unicorn/prefer-string-replace-all": "off",
    },
    languageOptions: {
      globals: {
        runCli: "readonly",
        runFormatTest: "readonly",
      },
    },
  },
  {
    files: ["src/cli/**/*.js"],
    rules: {
      "n/no-restricted-import": [
        "error",
        [
          {
            name: [
              toPath("src/**"),
              `!${toPath("src/cli/**")}`,
              `!${toPath("src/index.js")}`,
            ],
            message: "Don't use code from other directory.",
          },
        ],
      ],
    },
  },
  {
    files: ["src/language-js/needs-parens.js"],
    rules: {
      "prettier-internal-rules/better-parent-property-check-in-needs-parens":
        "error",
    },
  },
  {
    files: ["src/**/*.js"],
    rules: {
      "prettier-internal-rules/flat-ast-path-call": "error",
      "prettier-internal-rules/no-conflicting-comment-check-flags": "error",
      "prettier-internal-rules/no-doc-public-import": "error",
      "prettier-internal-rules/no-empty-flat-contents-for-if-break": "error",
      "prettier-internal-rules/no-unnecessary-ast-path-call": "error",
      "prettier-internal-rules/prefer-ast-path-each": "error",
      "prettier-internal-rules/prefer-indent-if-break": "error",
      "prettier-internal-rules/prefer-is-non-empty-array": "error",
      "prettier-internal-rules/prefer-ast-path-getters": "error",
    },
  },
  {
    files: ["src/language-*/**/*.js"],
    rules: {
      "prettier-internal-rules/directly-loc-start-end": "error",
    },
  },
  {
    files: ["src/language-js/**/*.js"],
    ignores: ["src/language-js/parse/postprocess/*.js"],
    rules: {
      "prettier-internal-rules/no-node-comments": [
        "error",
        {
          file: "src/language-js/utils/index.js",
          functions: ["hasComment", "getComments"],
        },
        "src/language-js/pragma.js",
        "src/language-js/parse/babel.js",
        "src/language-js/parse/meriyah.js",
        "src/language-js/parse/json.js",
        "src/language-js/parse/acorn.js",
        "src/language-js/parse/utils/wrap-babel-expression.js",
      ],
      "prettier-internal-rules/prefer-create-type-check-function": [
        "error",
        {
          ignoreSingleType: true,
          onlyTopLevelFunctions: true,
        },
      ],
    },
  },
  {
    files: ["website/**/*"],
    ...eslintPluginReact.configs.flat.recommended,
  },
  {
    files: ["website/**/*"],
    languageOptions: {
      globals: { ...globals.browser, ...globals.worker },
    },
    settings: {
      react: {
        version: "18",
      },
    },
    rules: {
      "react/display-name": "off",
      "react/no-deprecated": "off",
      "react/prop-types": "off",
      "unicorn/filename-case": "off",
    },
  },
  {
    files: ["website/playground/**/*"],
    languageOptions: {
      sourceType: "module",
    },
  },
  {
    files: ["bin/prettier.cjs"],
    languageOptions: {
      ecmaVersion: 5,
    },
    rules: {
      "no-var": "off",
      "prefer-arrow-callback": "off",
    },
  },
];