switch to github fetch

Github/fetch has merged PR for UMD distribution:
JakeChampion/fetch#616

Also abort support has been added:
JakeChampion/fetch#592

We can use Github fetch instead of yetch now.
But AbortableFetch is still not supported, see comment
in test.

karma.conf.js

@@ -21,7 +21,7 @@ module.exports = function(config) {
       'bower_components/jquery/dist/jquery.js',
       'node_modules/es6-promise/dist/es6-promise.auto.js',
       'node_modules/abortcontroller-polyfill/dist/abortcontroller-polyfill-only.js',
-      'assets/yetch-ponyfill.js',
+      'node_modules/whatwg-fetch/dist/fetch.umd.js',
       'pretender.js',
       'test/**/*.js'
     ],

package.json

@@ -40,14 +40,15 @@
   "dependencies": {
     "fake-xml-http-request": "^2.0.0",
     "route-recognizer": "^0.3.3",
-    "yetch": "^0.0.1"
+    "whatwg-fetch": "^2.0.4"
   },
   "jspm": {
     "shim": {
       "pretender": {
         "deps": [
           "route-recognizer",
-          "fake-xml-http-request"
+          "fake-xml-http-request",
+          "whatwg-fetch"
         ],
         "exports": "Pretender"
       }

pretender.js

@@ -14,7 +14,7 @@ var FakeXMLHttpRequest = appearsBrowserified ? getModuleDefault(require('fake-xm
   self.FakeXMLHttpRequest;
 
 // fetch related ponyfills
-var Yetch = appearsBrowserified ? getModuleDefault(require('yetch/dist/yetch-polyfill')) : self.Yetch;
+var WHATWGFetch = appearsBrowserified ? getModuleDefault(require('whatwg-fetch')) : self.WHATWGFetch;
 
 /**
  * parseURL - decompose a URL into its parts
@@ -147,7 +147,7 @@ function Pretender(/* routeMap1, routeMap2, ..., options*/) {
   this._fetchProps = ['fetch', 'Headers', 'Request', 'Response'];
   this._fetchProps.forEach(function(name) {
     this['_native' + name] = self[name];
-    self[name] = Yetch[name];
+    self[name] = WHATWGFetch[name];
   }, this);
 
   // 'start' the server

test/fetch_test.js

@@ -63,6 +63,36 @@ describe('pretender invoking by fetch', function(config) {
     assert.equal(val, 0);
   });
 
+
+  // TODO: Pretender doesn't work with abortable fetch
+  // src in fake_xml_http_request.js
+  // ```
+  // abort: function abort() {
+  //   this.aborted = true;
+  //   this.responseText = null;
+  //   this.errorFlag = true;
+  //   this.requestHeaders = {};
+
+  //   if (this.readyState > FakeXMLHttpRequest.UNSENT && this.sendFlag) {
+  //     this._readyStateChange(FakeXMLHttpRequest.DONE);
+  //     this.sendFlag = false;
+  //   }
+
+  //   this.readyState = FakeXMLHttpRequest.UNSENT;
+
+  //   this.dispatchEvent(new _Event("abort", false, false, this));
+  //   if (typeof this.onerror === "function") {
+  //       this.onerror();
+  //   }
+  // }
+  // ```
+  // For `fake_xml_http_request` impl, the request is resolved once its state
+  // is changed to `DONE` so the `reject` is not cathed.
+  // So the senario happens in pretender is:
+  // 1. state chagne to `DONE`, trigger resolve request
+  // 2. abort, trigger reject
+  // 3. xhr.onerror, trigger reject
+  // The first resolve wins, error thus not rejected but an empty request is resolved.
   it('has NO Abortable fetch', function(assert) {
     assert.expect(1);
     var done = assert.async();
@@ -87,15 +117,6 @@ describe('pretender invoking by fetch', function(config) {
       })
       .catch(function(err) {
         // it should execute to here but won't due to FakeXmlHttpRequest limitation
-        //
-        // ### why it's not working for fetch
-        // For `fake_xml_http_request` impl, the request is resolved once its state
-        // is changed to `DONE` so the `reject` is not cathed.
-        // So the senario happens in pretender is:
-        // 1. state chagne to `DONE`, trigger resolve request
-        // 2. abort, trigger reject
-        // 3. xhr.onerror, trigger reject
-        // The first resolve wins, error thus not rejected but an empty request is resolved.
         done();
       });
   });