Convert to ESM

* Load yargs as CJS due to strange compatibility issues
* Keep line number parsing code as CJS because it attempts to lazy-load dependencies
* Shared workers are always loaded through a dynamic import
* Shared worker filenames must now be file:// URLs, but you can provide a URL instance
* Test file paths within shared workers are now file:// URLs
* Error serialization and code excerpts now support ESM
* Title prefixes in the reporters now correctly skip all test file extensions, not just `js`

.xo-config.json

@@ -0,0 +1,76 @@
+{
+	"ignores": [
+		"media/**",
+		"test/config/fixtures/config-errors/test.js",
+		"test-tap/fixture/snapshots/test-sourcemaps/build/**",
+		"test-tap/fixture/report/edgecases/ast-syntax-error.cjs"
+	],
+	"rules": {
+		"import/no-anonymous-default-export": "off",
+		"import/no-mutable-exports": "off",
+		"import/order": [
+			"error",
+			{
+				"alphabetize": {
+					"order": "asc"
+				},
+				"newlines-between": "always"
+			}
+		],
+		"import/newline-after-import": "error",
+		"node/no-unsupported-features/es-syntax": "off",
+		"no-use-extend-native/no-use-extend-native": "off"
+	},
+	"overrides": [
+		{
+			"files": "index.d.ts",
+			"rules": {
+				"@typescript-eslint/member-ordering": "off",
+				"@typescript-eslint/method-signature-style": "off",
+				"@typescript-eslint/prefer-readonly-parameter-types": "off",
+				"@typescript-eslint/prefer-function-type": "off",
+				"@typescript-eslint/unified-signatures": "off"
+			}
+		},
+		{
+			"files": "plugin.d.ts",
+			"rules": {
+				"node/prefer-global/url": "off"
+			}
+		},
+		{
+			"files": "test-{d,tap}/**/*.ts",
+			"rules": {
+				"@typescript-eslint/explicit-function-return-type": "off",
+				"@typescript-eslint/no-empty-function": "off",
+				"@typescript-eslint/no-unsafe-call": "off",
+				"@typescript-eslint/no-unsafe-member-access": "off",
+				"@typescript-eslint/no-unsafe-return": "off",
+				"@typescript-eslint/no-unused-vars": "off",
+				"@typescript-eslint/prefer-readonly-parameter-types": "off",
+				"import/extensions": "off",
+				"no-unused-vars": "off"
+			}
+		},
+		{
+			"files": "test-tap/**/*.js",
+			"rules": {
+				"promise/prefer-await-to-then": "off",
+				"unicorn/error-message": "off",
+				"unicorn/no-array-reduce": "off",
+				"unicorn/prevent-abbreviations": "off"
+			}
+		},
+		{
+			"files": [
+				"test-tap/fixture/**",
+				"test/**/fixtures/**"
+			],
+			"rules": {
+				"ava/no-todo-test": "off",
+				"import/no-extraneous-dependencies": "off",
+				"import/no-unresolved": "off"
+			}
+		}
+	]
+}

entrypoints/cli.mjs

@@ -1,3 +1,4 @@
 #!/usr/bin/env node
-import * as cli from '../lib/cli.js'; // eslint-disable-line import/extensions
-cli.run();
+import run from '../lib/cli.js';
+
+run();

entrypoints/main.mjs

@@ -1,2 +1,3 @@
 import test from '../lib/worker/main.cjs';
+
 export default test;

lib/api.js

@@ -1,24 +1,25 @@
-'use strict';
-const fs = require('fs');
-const path = require('path');
-const os = require('os');
-const commonPathPrefix = require('common-path-prefix');
-const resolveCwd = require('resolve-cwd');
-const debounce = require('lodash/debounce');
-const arrify = require('arrify');
-const ms = require('ms');
-const chunkd = require('chunkd');
-const Emittery = require('emittery');
-const pMap = require('p-map');
-const tempDir = require('temp-dir');
-const globs = require('./globs');
-const isCi = require('./is-ci');
-const RunStatus = require('./run-status');
-const fork = require('./fork');
-const serializeError = require('./serialize-error');
-const {getApplicableLineNumbers} = require('./line-numbers');
-const sharedWorkers = require('./plugin-support/shared-workers');
-const scheduler = require('./scheduler');
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+
+import arrify from 'arrify';
+import chunkd from 'chunkd';
+import commonPathPrefix from 'common-path-prefix';
+import Emittery from 'emittery';
+import debounce from 'lodash/debounce.js';
+import ms from 'ms';
+import pMap from 'p-map';
+import resolveCwd from 'resolve-cwd';
+import tempDir from 'temp-dir';
+
+import fork from './fork.js';
+import * as globs from './globs.js';
+import isCi from './is-ci.js';
+import {getApplicableLineNumbers} from './line-numbers.js';
+import {observeWorkerProcess} from './plugin-support/shared-workers.js';
+import RunStatus from './run-status.js';
+import scheduler from './scheduler.js';
+import serializeError from './serialize-error.js';
 
 function resolveModules(modules) {
 	return arrify(modules).map(name => {
@@ -41,7 +42,7 @@ function getFilePathPrefix(files) {
 	return commonPathPrefix(files);
 }
 
-class Api extends Emittery {
+export default class Api extends Emittery {
 	constructor(options) {
 		super();
 
@@ -233,7 +234,7 @@ class Api extends Emittery {
 
 				const worker = fork(file, options, apiOptions.nodeArguments);
 				runStatus.observeWorker(worker, file, {selectingLines: lineNumbers.length > 0});
-				deregisteredSharedWorkers.push(sharedWorkers.observeWorkerProcess(worker, runStatus));
+				deregisteredSharedWorkers.push(observeWorkerProcess(worker, runStatus));
 
 				pendingWorkers.add(worker);
 				worker.promise.then(() => {
@@ -282,5 +283,3 @@ class Api extends Emittery {
 		return cacheDir;
 	}
 }
-
-module.exports = Api;

lib/assert.js

@@ -1,10 +1,10 @@
-'use strict';
-const concordance = require('concordance');
-const isError = require('is-error');
-const isPromise = require('is-promise');
-const concordanceOptions = require('./concordance-options').default;
-const {CIRCULAR_SELECTOR, isLikeSelector, selectComparable} = require('./like-selector');
-const snapshotManager = require('./snapshot-manager');
+import concordance from 'concordance';
+import isError from 'is-error';
+import isPromise from 'is-promise';
+
+import concordanceOptions from './concordance-options.js';
+import {CIRCULAR_SELECTOR, isLikeSelector, selectComparable} from './like-selector.js';
+import {SnapshotError, VersionMismatchError} from './snapshot-manager.js';
 
 function formatDescriptorDiff(actualDescriptor, expectedDescriptor, options) {
 	options = {...options, ...concordanceOptions};
@@ -35,7 +35,7 @@ const notImplemented = () => {
 	throw new Error('not implemented');
 };
 
-class AssertionError extends Error {
+export class AssertionError extends Error {
 	constructor(options) {
 		super(options.message || '');
 		this.name = 'AssertionError';
@@ -58,9 +58,8 @@ class AssertionError extends Error {
 		this.savedError = options.savedError ? options.savedError : getErrorWithLongStackTrace();
 	}
 }
-exports.AssertionError = AssertionError;
 
-function checkAssertionMessage(assertion, message) {
+export function checkAssertionMessage(assertion, message) {
 	if (typeof message === 'undefined' || typeof message === 'string') {
 		return true;
 	}
@@ -73,8 +72,6 @@ function checkAssertionMessage(assertion, message) {
 	});
 }
 
-exports.checkAssertionMessage = checkAssertionMessage;
-
 function getErrorWithLongStackTrace() {
 	const limitBefore = Error.stackTraceLimit;
 	Error.stackTraceLimit = Number.POSITIVE_INFINITY;
@@ -254,7 +251,7 @@ function assertExpectations({assertion, actual, expectations, message, prefix, s
 	}
 }
 
-class Assertions {
+export class Assertions {
 	constructor({
 		pass = notImplemented,
 		pending = notImplemented,
@@ -756,12 +753,12 @@ class Assertions {
 			try {
 				result = compareWithSnapshot({expected, message});
 			} catch (error) {
-				if (!(error instanceof snapshotManager.SnapshotError)) {
+				if (!(error instanceof SnapshotError)) {
 					throw error;
 				}
 
 				const improperUsage = {name: error.name, snapPath: error.snapPath};
-				if (error instanceof snapshotManager.VersionMismatchError) {
+				if (error instanceof VersionMismatchError) {
 					improperUsage.snapVersion = error.snapVersion;
 					improperUsage.expectedVersion = error.expectedVersion;
 				}
@@ -990,4 +987,3 @@ class Assertions {
 		}
 	}
 }
-exports.Assertions = Assertions;

lib/chalk.js

@@ -1,20 +1,16 @@
-'use strict';
-const chalk = require('chalk');
+import chalk from 'chalk';
 
-let ctx = null;
-exports.get = () => {
-	if (!ctx) {
-		throw new Error('Chalk has not yet been configured');
-	}
+let instance = new chalk.Instance();
+export default instance;
 
-	return ctx;
-};
+export {instance as chalk};
 
-exports.set = options => {
-	if (ctx) {
+let configured = false;
+export function set(options) {
+	if (configured) {
 		throw new Error('Chalk has already been configured');
 	}
 
-	ctx = new chalk.Instance(options);
-	return ctx;
-};
+	configured = true;
+	instance = new chalk.Instance(options);
+}