Allow to use native promises instead of RSVP

.travis.yml

@@ -33,6 +33,7 @@ jobs:
         - yarn lint:js
         - yarn test
         - PREFER_NATIVE=true yarn test
+        - NATIVE_PROMISE=true yarn test
         - npm run test:node
 
     - name: "Floating Dependencies"

README.md

@@ -91,6 +91,20 @@ If all your [browser targets](https://guides.emberjs.com/release/configuring-emb
 
 The way you do import remains same.
 
+### Use native promise instead of RSVP
+
+If you do not want to use RSVP, but native Promises, you can specify this build config flag:
+
+```js
+// ember-cli-build.js
+let app = new EmberAddon(defaults, {
+  // Add options here
+  'ember-fetch': {
+    nativePromise: true
+  }
+});
+```
+
 ### Error Handling
 
 A `fetch` response is successful if `response.ok` is true,

assets/browser-fetch.js.t

@@ -1,6 +1,5 @@
 (function (originalGlobal) {
   <%= moduleHeader %>
-    var Promise = RSVP.Promise;
     var supportProps = [
       'FormData',
       'FileReader',

ember-cli-build.js

@@ -6,6 +6,7 @@ module.exports = function(defaults) {
   let app = new EmberAddon(defaults, {
     // Add options here
     'ember-fetch': {
+      nativePromise: process.env.NATIVE_PROMISE ? true : false,
       preferNative: process.env.PREFER_NATIVE ? true : false
     }
   });

index.js

@@ -91,6 +91,7 @@ module.exports = {
 
     app._fetchBuildConfig = Object.assign({
       preferNative: false,
+      nativePromise: false,
       alwaysIncludePolyfill: false,
       hasEmberSourceModules,
       browsers: this.project.targets && this.project.targets.browsers
@@ -221,22 +222,48 @@ module.exports = {
       sourceMapConfig: { enabled: false }
     }), 'after-concat');
 
-    const moduleHeader = options.hasEmberSourceModules ? `
-  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');
+    const moduleHeader = this._getModuleHeader(options);
+
+    return debug(
+      new Template(polyfillNode, TEMPLATE_PATH, function (content) {
+        return {
+          moduleHeader,
+          moduleBody: content,
+        };
+      }),
+      "browser-fetch"
+    );
+  },
+
+  _getModuleHeader({ hasEmberSourceModules, nativePromise }) {
+    if (hasEmberSourceModules && nativePromise) {
+      return `
+define('fetch', ['exports', 'ember'], function(exports, Ember__module) {
+  'use strict';
+  var Ember = 'default' in Ember__module ? Ember__module['default'] : Ember__module;`;
+    }
+
+    if (hasEmberSourceModules) {
+      return `
+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;
+  var Promise = RSVP.Promise;`;
+    }
+
+    if (nativePromise) {
+      return `
+define('fetch', ['exports'], function(exports) {
+  'use strict';
+  var Ember = originalGlobal.Ember;`;
+    }
+
+    return `
+define('fetch', ['exports'], function(exports) {
+  'use strict';
+  var Ember = originalGlobal.Ember;
+  var Promise = Ember.RSVP.Promise;`;
   },
 
   _checkSupports(featureName, browsers) {