Use Rollup to build also as ESM

.babelrc

@@ -1,3 +1,3 @@
 {
- "presets": [ "es2015" ]
+  "presets": [ "@babel/preset-env" ]
 }

loader.js

@@ -1,7 +1,7 @@
 "use strict";
 
-const os = require('os');
-const gql = require('./src');
+import os from 'os';
+import gql from './src';
 
 // Takes `source` (the source GraphQL query string)
 // and `doc` (the parsed GraphQL document) and tacks on

package.json

@@ -3,8 +3,8 @@
   "version": "2.11.0",
   "description": "A JavaScript template literal tag that parses GraphQL queries",
   "main": "./lib/graphql-tag.umd.js",
-  "module": "./src/index.js",
-  "jsnext:main": "./src/index.js",
+  "module": "./lib/graphql-tag.js",
+  "jsnext:main": "./lib/graphql-tag.js",
   "sideEffects": false,
   "scripts": {
     "bundle": "rollup -c && cp src/index.js.flow lib/graphql-tag.umd.js.flow",
@@ -23,15 +23,19 @@
   "homepage": "https://github.com/apollographql/graphql-tag#readme",
   "dependencies": {},
   "devDependencies": {
-    "babel-preset-es2015": "^6.9.0",
-    "babel-register": "^6.9.0",
-    "chai": "^4.0.2",
-    "graphql": "^15.0.0",
-    "mocha": "^3.4.1",
-    "rollup": "^0.45.0",
-    "test-all-versions": "^3.3.2"
+    "@babel/core": "^7.12.10",
+    "@babel/preset-env": "^7.12.11",
+    "@babel/register": "^7.12.10",
+    "chai": "^4.2.0",
+    "graphql": "^15.4.0",
+    "mocha": "^8.2.1",
+    "rollup": "^2.37.0",
+    "test-all-versions": "^5.0.1"
   },
   "peerDependencies": {
     "graphql": "^0.9.0 || ^0.10.0 || ^0.11.0 || ^0.12.0 || ^0.13.0 || ^14.0.0 || ^15.0.0"
+  },
+  "mocha": {
+    "require": "@babel/register"
   }
 }

rollup.config.js

@@ -1,9 +1,22 @@
 export default {
-  entry: 'src/index.js',
-  dest: 'lib/graphql-tag.umd.js',
-  format: 'umd',
-  sourceMap: true,
-  moduleName: 'graphql-tag',
+  input: 'src/index.js',
+  output: [
+    {
+      file: 'lib/graphql-tag.js',
+      format: 'esm',
+      sourcemap: true
+    },
+    {
+      file: 'lib/graphql-tag.umd.js',
+      format: 'umd',
+      globals: {
+        'graphql/language': 'language'
+      },
+      name: 'graphql-tag',
+      sourcemap: true,
+      exports: 'named'
+    }
+  ],
   onwarn
 };
 

src/index.js

@@ -1,6 +1,4 @@
-var parser = require('graphql/language/parser');
-
-var parse = parser.parse;
+import { parse } from 'graphql/language';
 
 // Strip insignificant whitespace
 // Note that this could do a lot more, such as reorder fields etc.
@@ -177,4 +175,4 @@ gql.disableFragmentWarnings = disableFragmentWarnings;
 gql.enableExperimentalFragmentVariables = enableExperimentalFragmentVariables;
 gql.disableExperimentalFragmentVariables = disableExperimentalFragmentVariables;
 
-module.exports = gql;
+export default gql;

test/graphql.js

@@ -1,6 +1,7 @@
-const gql = require('../src');
-const loader = require('../loader');
-const assert = require('chai').assert;
+import { assert } from 'chai';
+
+import gql from '../src';
+import loader from '../loader';
 
 describe('gql', () => {
   it('parses queries', () => {