Output ESM instead of CommonJS (#225)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

.github/workflows/main.yml

@@ -18,9 +18,9 @@ jobs:
       - uses: actions/setup-node@v2
         with:
           node-version: ${{ matrix.node-version }}
-      - run: npm install
+      - run: npm install --force
       - run: npm test
       - uses: codecov/codecov-action@v1
-        if: matrix.node-version == 14
+        if: matrix.node-version == 16
         with:
           fail_ci_if_error: true

example.js

@@ -1,5 +1,4 @@
-'use strict';
-const {default: ow} = require('./dist');
+import ow from './dist/index.js'
 
 const logError = fn => {
 	try {

package.json

@@ -12,12 +12,13 @@
 		"email": "sindresorhus@gmail.com",
 		"url": "https://sindresorhus.com"
 	},
+	"type": "module",
 	"main": "dist/index.js",
 	"engines": {
 		"node": ">=12"
 	},
 	"scripts": {
-		"test": "xo && nyc ava",
+		"test": "xo && c8 ava",
 		"docs": "typedoc source/index.ts",
 		"build": "del-cli dist && tsc",
 		"prepare": "npm run build",
@@ -61,15 +62,15 @@
 		"@types/lodash.isequal": "^4.5.5",
 		"@types/node": "^16.10.2",
 		"@types/vali-date": "^1.0.0",
-		"ava": "^2.4.0",
+		"ava": "^3.15.0",
+		"c8": "^7.10.0",
 		"del-cli": "^4.0.0",
 		"expect-type": "^0.12.0",
 		"gh-pages": "^3.2.3",
-		"nyc": "^15.1.0",
-		"ts-node": "^10.2.1",
+		"ts-node": "^10.4.0",
 		"typedoc": "^0.22.5",
-		"typescript": "^4.4.3",
-		"xo": "^0.38.2"
+		"typescript": "^4.5.0-beta",
+		"xo": "^0.46.4"
 	},
 	"browser": {
 		"./dist/utils/infer-label.js": "./dist/utils/infer-label.browser.js"
@@ -93,25 +94,26 @@
 			"@typescript-eslint/no-explicit-any": "off",
 			"@typescript-eslint/no-empty-function": "off",
 			"@typescript-eslint/restrict-template-expressions": "off",
-			"@typescript-eslint/no-unused-vars": "off",
-			"import/no-anonymous-default-export": "off"
+			"@typescript-eslint/no-unused-vars": "off"
 		}
 	},
 	"ava": {
-		"babel": false,
-		"compileEnhancements": false,
+		"nonSemVerExperiments": {
+			"configurableModuleFormat": true
+		},
+		"nodeArguments": [
+			"--loader=ts-node/esm",
+			"--experimental-specifier-resolution=node"
+		],
 		"files": [
 			"test/**",
 			"!test/fixtures/**"
 		],
-		"extensions": [
-			"ts"
-		],
-		"require": [
-			"ts-node/register"
-		]
+		"extensions": {
+			"ts": "module"
+		}
 	},
-	"nyc": {
+	"c8": {
 		"reporter": [
 			"text",
 			"lcov"

source/argument-error.ts

@@ -1,4 +1,4 @@
-import {generateStackTrace} from './utils/generate-stack';
+import {generateStackTrace} from './utils/generate-stack.js';
 
 const wrapStackTrace = (error: ArgumentError, stack: string): string => `${error.name}: ${error.message}\n${stack}`;
 

source/index.ts

@@ -1,10 +1,10 @@
 import callsites from 'callsites';
-import {inferLabel} from './utils/infer-label';
-import {Predicate} from './predicates/predicate';
-import {BasePredicate, isPredicate} from './predicates/base-predicate';
-import modifiers, {Modifiers} from './modifiers';
-import predicates, {Predicates} from './predicates';
-import test from './test';
+import {inferLabel} from './utils/infer-label.js';
+import {Predicate} from './predicates/predicate.js';
+import {BasePredicate, isPredicate} from './predicates/base-predicate.js';
+import modifiers, {Modifiers} from './modifiers.js';
+import predicates, {Predicates} from './predicates.js';
+import test from './test.js';
 
 /**
 @hidden
@@ -124,7 +124,7 @@ Object.defineProperties(ow, {
 			} catch {
 				return false;
 			}
-		}
+		},
 	},
 	create: {
 		value: <T>(labelOrPredicate: BasePredicate<T> | string | undefined, predicate?: BasePredicate<T>) => (value: unknown, label?: string): asserts value is T => {
@@ -137,8 +137,8 @@ Object.defineProperties(ow, {
 			}
 
 			test(value, label ?? (labelOrPredicate!), predicate!);
-		}
-	}
+		},
+	},
 });
 
 // Can't use `export default predicates(modifiers(ow)) as Ow` because the variable needs a type annotation to avoid a compiler error when used:
@@ -149,5 +149,5 @@ const _ow: Ow = predicates(modifiers(ow)) as Ow;
 export default _ow;
 
 export {BasePredicate, Predicate};
-export * from './predicates';
-export {ArgumentError} from './argument-error';
+export * from './predicates.js';
+export {ArgumentError} from './argument-error.js';

source/modifiers.ts

@@ -1,5 +1,5 @@
-import {BasePredicate} from '.';
-import predicates, {Predicates} from './predicates';
+import predicates, {Predicates} from './predicates.js';
+import {BasePredicate} from './index.js';
 
 type Optionalify<P> = P extends BasePredicate<infer X>
 	? P & BasePredicate<X | undefined>
@@ -14,12 +14,14 @@ export interface Modifiers {
 	};
 }
 
-export default <T>(object: T): T & Modifiers => {
+const modifiers = <T>(object: T): T & Modifiers => {
 	Object.defineProperties(object, {
 		optional: {
-			get: (): Predicates => predicates({}, {optional: true})
-		}
+			get: (): Predicates => predicates({}, {optional: true}),
+		},
 	});
 
 	return object as T & Modifiers;
 };
+
+export default modifiers;

source/operators/not.ts

@@ -1,6 +1,6 @@
-import randomId from '../utils/random-id';
-import {validatorSymbol} from '../predicates/predicate';
-import type {Predicate, Validator} from '../predicates/predicate';
+import randomId from '../utils/random-id.js';
+import {validatorSymbol} from '../predicates/predicate.js';
+import type {Predicate, Validator} from '../predicates/predicate.js';
 
 /**
 Operator which inverts the following validation.
@@ -17,9 +17,9 @@ export const not = (predicate: Predicate): Predicate => {
 		const placeholder = randomId();
 
 		validator.message = (value: unknown, label: string): string => (
-			negatedMessage ?
-				negatedMessage(value, label) :
-				message(value, placeholder).replace(/ to /, '$&not ').replace(placeholder, label)
+			negatedMessage
+				? negatedMessage(value, label)
+				: message(value, placeholder).replace(/ to /, '$&not ').replace(placeholder, label)
 		);
 
 		validator.validator = (value: unknown): unknown => !fn(value);