Switch to isomorphic-fetch

package.json

@@ -63,9 +63,9 @@
   "dependencies": {
     "core-js": "^1.0.0",
     "loose-envify": "^1.0.0",
+    "isomorphic-fetch": "^2.1.1",
     "promise": "^7.0.3",
-    "ua-parser-js": "^0.7.9",
-    "whatwg-fetch": "^0.9.0"
+    "ua-parser-js": "^0.7.9"
   },
   "devEngines": {
     "node": ">=3",

scripts/babel/default-options.js

@@ -43,8 +43,8 @@ module.exports = {
   plugins: plugins,
   _moduleMap: {
     'core-js/library/es6/map': 'core-js/library/es6/map',
+    'isomorphic-fetch': 'isomorphic-fetch',
     'promise': 'promise',
     'ua-parser-js': 'ua-parser-js',
-    'whatwg-fetch': 'whatwg-fetch',
   },
 };

src/__forks__/fetch.js

@@ -11,5 +11,11 @@
 
 'use strict';
 
-require('whatwg-fetch');
-module.exports = self.fetch.bind(self);
+// This hopefully supports the React Native case, which is already bringing along
+// its own fetch polyfill. That should exist on `global`. If that doesn't exist
+// then we'll try to polyfill, which might not work correctly in all environments.
+if (global.fetch) {
+  module.exports = global.fetch.bind(global);
+} else {
+  module.exports = require('isomorphic-fetch');
+}