add pkg.module (Leaflet#6021)

* add pkg.module version

* get tests to pass

* export noConflict

build/rollup-config.js

@@ -3,8 +3,9 @@
 import rollupGitVersion from 'rollup-plugin-git-version'
 import json from 'rollup-plugin-json'
 import gitRev from 'git-rev-sync'
+import pkg from '../package.json'
 
-let version = require('../package.json').version;
+let {version} = pkg;
 let release;
 
 // Skip the git branch+rev in the banner when doing a release build
@@ -23,15 +24,33 @@ const banner = `/* @preserve
  */
 `;
 
+const outro = `var oldL = window.L;
+exports.noConflict = function() {
+	window.L = oldL;
+	return this;
+}
+
+// Always export us to window global (see #2364)
+window.L = exports;`;
+
 export default {
 	input: 'src/Leaflet.js',
-	output: {
-		file: 'dist/leaflet-src.js',
-		format: 'umd',
-		name: 'L',
-		banner: banner,
-		sourcemap: true
-	},
+	output: [
+		{
+			file: pkg.main,
+			format: 'umd',
+			name: 'L',
+			banner: banner,
+			outro: outro,
+			sourcemap: true
+		},
+		{
+			file: pkg.module,
+			format: 'es',
+			banner: banner,
+			sourcemap: true
+		}
+	],
 	legacy: true, // Needed to create files loadable by IE8
 	plugins: [
 		release ? json() : rollupGitVersion()

package.json

@@ -32,6 +32,7 @@
     "uglify-js": "~3.0.26"
   },
   "main": "dist/leaflet-src.js",
+  "module": "dist/leaflet-src.esm.js",
   "style": "dist/leaflet.css",
   "files": [
     "dist",

spec/karma.conf.js

@@ -1,5 +1,14 @@
 var json = require('rollup-plugin-json');
 
+const outro = `var oldL = window.L;
+exports.noConflict = function() {
+	window.L = oldL;
+	return this;
+}
+
+// Always export us to window global (see #2364)
+window.L = exports;`;
+
 // Karma configuration
 module.exports = function (config) {
 
@@ -50,7 +59,8 @@ module.exports = function (config) {
 				json()
 			],
 			format: 'umd',
-			name: 'L'
+			name: 'L',
+			outro: outro
 		},
 
 		// test results reporter to use

src/Leaflet.js

@@ -23,16 +23,5 @@ export * from './layer/index';
 // map
 export * from './map/index';
 
-// misc
-
-var oldL = window.L;
-export function noConflict() {
-	window.L = oldL;
-	return this;
-}
-
-// Always export us to window global (see #2364)
-window.L = exports;
-
 import {freeze} from './core/Util';
 Object.freeze = freeze;