fix: enable es modules

.travis.yml

@@ -1,5 +1,6 @@
 language: node_js
 node_js:
+  - '14'
   - '12'
   - '10'
   - '8'

estest/index.js

@@ -0,0 +1,26 @@
+// eslint-disable-next-line unicorn/import-index,import/extensions,import/no-useless-path-segments
+import meow from '../index.js';
+
+console.log(
+	meow(
+		`
+Usage
+  $ estest <input>
+
+Options
+  --rainbow, -r  Include a rainbow
+
+Examples
+  $ estest unicorns --rainbow
+  🌈 unicorns 🌈
+`,
+		{
+			flags: {
+				rainbow: {
+					type: 'boolean',
+					alias: 'r'
+				}
+			}
+		}
+	)
+);

estest/package.json

@@ -0,0 +1,4 @@
+{
+    "name": "estest",
+    "type": "module"
+}

index.js

@@ -12,7 +12,10 @@ const normalizePackageData = require('normalize-package-data');
 
 // Prevent caching of this module so module.parent is always accurate
 delete require.cache[__filename];
-const parentDir = path.dirname(module.parent.filename);
+
+// In CJS module.parent is available but not in ES modules
+const parentFilename = module.parent ? module.parent.filename : Object.keys(require.cache)[0];
+const parentDirectory = path.dirname(parentFilename);
 
 const meow = (helpText, options) => {
 	if (typeof helpText !== 'string') {
@@ -22,7 +25,7 @@ const meow = (helpText, options) => {
 
 	options = {
 		pkg: readPkgUp.sync({
-			cwd: parentDir,
+			cwd: parentDirectory,
 			normalize: false
 		}).packageJson || {},
 		argv: process.argv.slice(2),

test.js

@@ -1,6 +1,7 @@
 import test from 'ava';
 import indentString from 'indent-string';
 import execa from 'execa';
+import path from 'path';
 import pkg from './package.json';
 import meow from '.';
 
@@ -307,3 +308,14 @@ test('supports `number` flag type - throws on incorrect default value', t => {
 		});
 	});
 });
+
+test('supports es modules', async t => {
+	try {
+		const {stdout} = await execa('node', ['index.js'], {
+			cwd: path.join(__dirname, 'estest')
+		});
+		t.regex(stdout, /rainbow: false/);
+	} catch (error) {
+		t.is(error, undefined);
+	}
+});