Fix Ember global deprecation

A minimal fix for #600. We should probably follow through with the
refactor suggested by @rwjblue in #600 but that can be done later.

This is probably not very embroider friendly, but neither is the
current code. It's probably easier to just rewrite the shims in
terms of ES modules and embroider macros, i.e. what was suggested
in #337.

assets/browser-fetch.js.t

@@ -1,7 +1,5 @@
 (function (originalGlobal) {
-  define('fetch', ['exports'], function(exports) {
-    'use strict';
-    var Promise = originalGlobal.Ember.RSVP.Promise;
+  <%= moduleHeader %>
     var supportProps = [
       'FormData',
       'FileReader',
@@ -49,8 +47,8 @@
       return result;
     }
 
-    if (originalGlobal.Ember.Test) {
-      originalGlobal.Ember.Test.registerWaiter(function() {
+    if (Ember.Test) {
+      Ember.Test.registerWaiter(function() {
         return pending === 0;
       });
 

index.js

@@ -27,6 +27,7 @@ const map = stew.map;
 const Rollup = require('broccoli-rollup');
 const BroccoliDebug = require('broccoli-debug');
 const calculateCacheKeyForTree = require('calculate-cache-key-for-tree');
+const VersionChecker = require('ember-cli-version-checker');
 
 const debug = BroccoliDebug.buildDebugCallback('ember-fetch');
 
@@ -172,6 +173,7 @@ module.exports = {
     const alwaysIncludePolyfill = !options.preferNative || options.alwaysIncludePolyfill;
     const needsFetchPolyfill = alwaysIncludePolyfill || !this._checkSupports('fetch', browsers);
     const needsAbortControllerPolyfill = alwaysIncludePolyfill || !this._checkSupports('abortcontroller', browsers);
+    const hasRealModules = VersionChecker.forProject(this.project).check({ 'ember-source': '>= 3.27.0' });
 
     const inputNodes = [];
     const inputFiles = [];
@@ -216,8 +218,19 @@ module.exports = {
       sourceMapConfig: { enabled: false }
     }), 'after-concat');
 
+    const moduleHeader = hasRealModules ? `
+  define('fetch', ['exports', 'ember', 'rsvp'], function(exports, Ember__module, RSVP__module) {
+    'use strict';
+    var Ember = 'default' in Ember__module ? Ember__module['default'] : Ember__module;
+    var RSVP = 'default' in RSVP__module ? RSVP__module['default'] : RSVP__module;` : `
+  define('fetch', ['exports'], function(exports) {
+    'use strict';
+    var Ember = originalGlobal.Ember;
+    var RSVP = Ember.RSVP;`
+
     return debug(new Template(polyfillNode, TEMPLATE_PATH, function(content) {
       return {
+        moduleHeader,
         moduleBody: content
       };
     }), 'browser-fetch');

package.json

@@ -36,6 +36,7 @@
     "caniuse-api": "^3.0.0",
     "ember-cli-babel": "^7.23.1",
     "ember-cli-typescript": "^3.1.3",
+    "ember-cli-version-checker": "^5.1.2",
     "node-fetch": "^2.6.1",
     "whatwg-fetch": "^3.6.2"
   },