enable chaining of chai plugins

lib/chai.js

@@ -13,8 +13,6 @@ import {Assertion} from './chai/assertion.js';
 import * as should from './chai/interface/should.js';
 import {assert} from './chai/interface/assert.js';
 
-const used = [];
-
 // Assertion Error
 export {AssertionError};
 
@@ -35,16 +33,14 @@ export function use(fn) {
  expect,
  assert,
  Assertion,
- ...should
+ use,
+ ...should,
  };
 
- if (!~used.indexOf(fn)) {
- fn(exports, util);
- used.push(fn);
- }
+ fn(exports, util);
 
  return exports;
-};
+}
 
 // Utility Functions
 export {util};

test/plugins.js

@@ -1,42 +1,40 @@
-import * as chai from '../index.js';
+import {use, expect} from '../index.js';
 
-describe('plugins', function () {
+function plugin(chai) {
+ if (chai.Assertion.prototype.testing) return;
+
+ Object.defineProperty(chai.Assertion.prototype, 'testing', {
+ get: function () {
+ return 'successful';
+ },
+ });
+}
 
- function plugin (chai) {
-  if (chai.Assertion.prototype.testing) return;
+function anotherPlugin(chai) {
+ if (chai.Assertion.prototype.moreTesting) return;
 
-  Object.defineProperty(chai.Assertion.prototype, 'testing', {
-  get: function () {
-  return 'successful';
-  }
-  });
- }
+ Object.defineProperty(chai.Assertion.prototype, 'moreTesting', {
+ get: function () {
+ return 'more success';
+ },
+ });
+}
 
+describe('plugins', function () {
  it('basic usage', function () {
- chai.use(plugin);
- var expect = chai.expect;
+ const {expect} = use(plugin);
  expect(expect('').testing).to.equal('successful');
  });
 
- it('double plugin', function () {
- chai.expect(function () {
- chai.use(plugin);
+ it('multiple plugins', function () {
+ expect(function () {
+ use(plugin).use(anotherPlugin);
  }).to.not.throw();
  });
 
  it('.use detached from chai object', function () {
- function anotherPlugin (chai) {
- Object.defineProperty(chai.Assertion.prototype, 'moreTesting', {
- get: function () {
- return 'more success';
- }
- });
- }
-
- var use = chai.use;
- use(anotherPlugin);
-
- var expect = chai.expect;
+ const {expect} = use(anotherPlugin);
+
  expect(expect('').moreTesting).to.equal('more success');
  });
 });