feat: add ESM export; fixes mochajs#5211

.gitignore

@@ -4,6 +4,8 @@ docs/images/supporters
 docs/api
 mocha.js
 mocha.js.map
+mocha.mjs
+mocha.mjs.map
 .karma/
 !bin/mocha.js
 !lib/mocha.js

eslint.config.js

@@ -151,7 +151,8 @@ module.exports = [
       'out/**',
       'test/integration/fixtures/**',
       '.karma/**',
-      'mocha.js'
+      'mocha.js',
+      'mocha.mjs'
     ],
   }
 ];

karma.conf.js

@@ -317,6 +317,10 @@ const chooseTestSuite = (cfg, value) => {
           {
             pattern: 'test/browser-specific/esm.spec.mjs',
             type: 'module'
+          },
+          {
+            pattern: 'test/browser-specific/esm-build.spec.mjs',
+            type: 'module'
           }
         ]
       });

package.json

@@ -177,6 +177,8 @@
     "mocha.css",
     "mocha.js",
     "mocha.js.map",
+    "mocha.mjs",
+    "mocha.mjs.map",
     "browser-entry.js"
   ],
   "browser": {

rollup.config.js

@@ -10,37 +10,43 @@ import {visualizer} from 'rollup-plugin-visualizer';
 import pickFromPackageJson from './scripts/pick-from-package-json';
 import {version} from './package.json';
 
-const config = {
-  input: './browser-entry.js',
-  output: {
-    file: './mocha.js',
-    format: 'umd',
-    sourcemap: true,
-    name: 'mocha',
-    banner: `// mocha@${version} in javascript ES2018`
-  },
-  plugins: [
-    json(),
-    pickFromPackageJson({
-      keys: ['name', 'version', 'homepage', 'notifyLogo']
-    }),
-    commonjs(),
-    globals(),
-    nodePolyfills(),
-    nodeResolve({
-      browser: true
-    })
-  ],
-  onwarn: (warning, warn) => {
-    if (warning.code === 'CIRCULAR_DEPENDENCY') return;
+function getConfig (format) {
+  const config = {
+    input: './browser-entry.js',
+    output: {
+      file: `./mocha${format === 'esm' ? '.mjs' : '.js'}`,
+      format,
+      sourcemap: true,
+      name: 'mocha',
+      banner: `// mocha@${version} in javascript ES2018`
+    },
+    plugins: [
+      json(),
+      pickFromPackageJson({
+        keys: ['name', 'version', 'homepage', 'notifyLogo']
+      }),
+      commonjs(),
+      globals(),
+      nodePolyfills(),
+      nodeResolve({
+        browser: true
+      })
+    ],
+    onwarn: (warning, warn) => {
+      if (warning.code === 'CIRCULAR_DEPENDENCY') return;
 
-    // Use default for everything else
-    warn(warning);
-  }
-};
+      // Use default for everything else
+      warn(warning);
+    }
+  };
 
-if (!process.env.CI) {
-  config.plugins.push(visualizer());
+  if (!process.env.CI) {
+    config.plugins.push(visualizer());
+  }
+  return config;
 }
 
-export default config;
+export default [
+  getConfig('umd'),
+  getConfig('esm')
+];

test/browser-specific/esm-build.spec.mjs

@@ -0,0 +1,9 @@
+import './fixtures/esm-build.fixture.mjs';
+
+it('should register a global if it did not fail', function () {
+  expect(window.MOCHA_IS_OK, 'to be ok');
+});
+
+it('should have a global Mocha', function () {
+  expect(window.Mocha, 'not to be', undefined);
+});

test/browser-specific/fixtures/esm-build.fixture.mjs

@@ -0,0 +1,3 @@
+/* eslint-disable-next-line import/no-absolute-path */
+import '/base/mocha.mjs';
+window.MOCHA_IS_OK = true;