Breaking: provide ESM export (refs eslint/rfcs#72)

.eslintignore

@@ -1,4 +1,4 @@
-!.eslintrc.js
+!.eslintrc.cjs
 /node_modules
 /tests/fixtures
 /tools

.eslintrc.cjs

@@ -0,0 +1,23 @@
+module.exports = {
+    root: true,
+    extends: "eslint:recommended",
+    parserOptions: {
+        sourceType: "module"
+    },
+    env: {
+        es6: true,
+        node: true
+    },
+    overrides: [
+        {
+            files: ["tests/lib/*"],
+            parserOptions: {
+                ecmaVersion: 2020,
+                sourceType: "module"
+            },
+            env: {
+                mocha: true
+            }
+        }
+    ]
+};

.gitignore

@@ -1,6 +1,8 @@
 build
 coverage
 node_modules
+.DS_Store
+dist
 npm-debug.log
 _test.js
 .idea

espree.js

@@ -56,13 +56,14 @@
  */
 /* eslint no-undefined:0, no-use-before-define: 0 */
 
-"use strict";
+import * as acorn from "acorn";
+import jsx from "acorn-jsx";
+import astNodeTypes from "./lib/ast-node-types.js";
+import espree from "./lib/espree.js";
+import espreeVersion from "./lib/version.js";
+import visitorKeys from "eslint-visitor-keys";
+import { getLatestEcmaVersion, getSupportedEcmaVersions } from "./lib/options.js";
 
-const acorn = require("acorn");
-const jsx = require("acorn-jsx");
-const astNodeTypes = require("./lib/ast-node-types");
-const espree = require("./lib/espree");
-const { getLatestEcmaVersion, getSupportedEcmaVersions } = require("./lib/options");
 
 // To initialize lazily.
 const parsers = {
@@ -106,7 +107,7 @@ const parsers = {
  * @throws {SyntaxError} If the input code is invalid.
  * @private
  */
-function tokenize(code, options) {
+export function tokenize(code, options) {
     const Parser = parsers.get(options);
 
     // Ensure to collect tokens.
@@ -128,7 +129,7 @@ function tokenize(code, options) {
  * @returns {ASTNode} The "Program" AST node.
  * @throws {SyntaxError} If the input code is invalid.
  */
-function parse(code, options) {
+export function parse(code, options) {
     const Parser = parsers.get(options);
 
     return new Parser(options, code).parse();
@@ -138,15 +139,12 @@ function parse(code, options) {
 // Public
 //------------------------------------------------------------------------------
 
-exports.version = require("./package.json").version;
+export const version = espreeVersion;
 
-exports.tokenize = tokenize;
-
-exports.parse = parse;
 
 // Deep copy.
 /* istanbul ignore next */
-exports.Syntax = (function() {
+export const Syntax = (function() {
     let name,
         types = {};
 
@@ -168,10 +166,10 @@ exports.Syntax = (function() {
 }());
 
 /* istanbul ignore next */
-exports.VisitorKeys = (function() {
-    return require("eslint-visitor-keys").KEYS;
+export const VisitorKeys = (function() {
+    return visitorKeys.KEYS;
 }());
 
-exports.latestEcmaVersion = getLatestEcmaVersion();
+export const latestEcmaVersion = getLatestEcmaVersion();
 
-exports.supportedEcmaVersions = getSupportedEcmaVersions();
+export const supportedEcmaVersions = getSupportedEcmaVersions();

lib/ast-node-types.js

@@ -3,8 +3,6 @@
  * @author Nicholas C. Zakas
  */
 
-"use strict";
-
 //------------------------------------------------------------------------------
 // Requirements
 //------------------------------------------------------------------------------
@@ -15,7 +13,7 @@
 // Public
 //------------------------------------------------------------------------------
 
-module.exports = {
+export default {
     AssignmentExpression: "AssignmentExpression",
     AssignmentPattern: "AssignmentPattern",
     ArrayExpression: "ArrayExpression",

lib/espree.js

@@ -1,8 +1,7 @@
-"use strict";
-
 /* eslint-disable no-param-reassign*/
-const TokenTranslator = require("./token-translator");
-const { normalizeOptions } = require("./options");
+import TokenTranslator from "./token-translator.js";
+import { normalizeOptions } from "./options.js";
+
 
 const STATE = Symbol("espree's internal state");
 const ESPRIMA_FINISH_NODE = Symbol("espree's esprimaFinishNode");
@@ -41,7 +40,7 @@ function convertAcornCommentToEsprimaComment(block, text, start, end, startLoc,
     return comment;
 }
 
-module.exports = () => Parser => {
+export default () => Parser => {
     const tokTypes = Object.assign({}, Parser.acorn.tokTypes);
 
     if (Parser.acornJsx) {

lib/features.js

@@ -4,8 +4,6 @@
  * @author Nicholas C. Zakas
  */
 
-"use strict";
-
 //------------------------------------------------------------------------------
 // Requirements
 //------------------------------------------------------------------------------
@@ -16,7 +14,7 @@
 // Public
 //------------------------------------------------------------------------------
 
-module.exports = {
+export default {
 
     // React JSX parsing
     jsx: false,

lib/options.js

@@ -3,8 +3,6 @@
  * @author Kai Cataldo
  */
 
-"use strict";
-
 //------------------------------------------------------------------------------
 // Helpers
 //------------------------------------------------------------------------------
@@ -67,7 +65,7 @@ function normalizeSourceType(sourceType = "script") {
  * @throws {Error} throw an error if found invalid option.
  * @returns {Object} normalized options
  */
-function normalizeOptions(options) {
+export function normalizeOptions(options) {
     const ecmaVersion = normalizeEcmaVersion(options.ecmaVersion);
     const sourceType = normalizeSourceType(options.sourceType);
     const ranges = options.range === true;
@@ -83,24 +81,14 @@ function normalizeOptions(options) {
  * Get the latest ECMAScript version supported by Espree.
  * @returns {number} The latest ECMAScript version.
  */
-function getLatestEcmaVersion() {
+export function getLatestEcmaVersion() {
     return SUPPORTED_VERSIONS[SUPPORTED_VERSIONS.length - 1];
 }
 
 /**
  * Get the list of ECMAScript versions supported by Espree.
  * @returns {number[]} An array containing the supported ECMAScript versions.
  */
-function getSupportedEcmaVersions() {
+export function getSupportedEcmaVersions() {
     return [...SUPPORTED_VERSIONS];
 }
-
-//------------------------------------------------------------------------------
-// Public
-//------------------------------------------------------------------------------
-
-module.exports = {
-    normalizeOptions,
-    getLatestEcmaVersion,
-    getSupportedEcmaVersions
-};

lib/token-translator.js

@@ -4,8 +4,6 @@
  */
 /* eslint no-underscore-dangle: 0 */
 
-"use strict";
-
 //------------------------------------------------------------------------------
 // Requirements
 //------------------------------------------------------------------------------
@@ -260,4 +258,4 @@ TokenTranslator.prototype = {
 // Public
 //------------------------------------------------------------------------------
 
-module.exports = TokenTranslator;
+export default TokenTranslator;

lib/version.js

@@ -0,0 +1,3 @@
+const version = "7.3.1";
+
+export default version;

lib/visitor-keys.js

@@ -25,8 +25,6 @@
  * SOFTWARE.
  */
 
-"use strict";
-
 //------------------------------------------------------------------------------
 // Requirements
 //------------------------------------------------------------------------------
@@ -37,7 +35,7 @@
 // Public
 //------------------------------------------------------------------------------
 
-module.exports = {
+export default {
 
     // ECMAScript
     AssignmentExpression: ["left", "right"],