Remove unnecessary fetch polyfill from frontend

All supported browsers provide a native `fetch` implementation so
remove `isomorphic-fetch` from the polyfills.

Instead of this, we use `node-fetch` directly in the unit tests
and also update `fetch-mock` to the latest version.

These changes, along with the Node.js 14 update, reduce the execution
time for the full suite of unit tests from ~2.5mins to under 1 minute.

config_frontend/setupTests.js

@@ -12,10 +12,15 @@ limitations under the License.
 */
 
 import 'react-testing-library/cleanup-after-each';
+import fetch from 'node-fetch';
 import fetchMock from 'fetch-mock';
 import { TextDecoder, TextEncoder } from 'util';
 import { ReadableStream } from 'web-streams-polyfill/es6';
 
+if (!global.fetch) {
+  global.fetch = fetch;
+}
+
 fetchMock.catch();
 fetchMock.config.overwriteRoutes = true;
 

package.json

@@ -40,7 +40,6 @@
     "es6-promise": "^4.2.8",
     "git-url-parse": "^11.3.0",
     "history": "^4.10.1",
-    "isomorphic-fetch": "^2.2.1",
     "js-yaml": "^3.14.0",
     "lodash.isequal": "^4.5.0",
     "lodash.keyby": "^4.6.0",
@@ -90,7 +89,7 @@
     "eslint-plugin-notice": "^0.9.10",
     "eslint-plugin-prettier": "^3.1.4",
     "eslint-plugin-react": "^7.20.0",
-    "fetch-mock": "^7.7.3",
+    "fetch-mock": "^9.10.7",
     "fibers": "^5.0.0",
     "file-loader": "^6.0.0",
     "glob": "^7.1.6",
@@ -100,6 +99,7 @@
     "lodash.difference": "^4.5.0",
     "lodash.omit": "^4.5.0",
     "mini-css-extract-plugin": "^0.9.0",
+    "node-fetch": "^2.6.1",
     "prettier": "^2.0.5",
     "properties-reader": "^2.1.1",
     "react-testing-library": "^6.1.2",

src/api/extensions.test.js

@@ -29,7 +29,10 @@ it('getExtensions', () => {
 });
 
 it('getExtensions null', () => {
-  fetchMock.get(/extensions/, 'null');
+  fetchMock.get(/extensions/, {
+    body: 'null',
+    headers: { 'Content-Type': 'application/json' }
+  });
   return API.getExtensions().then(response => {
     expect(response).toEqual([]);
     fetchMock.restore();

src/utils/polyfills.js

@@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Tekton Authors
+Copyright 2019-2020 The Tekton Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -13,7 +13,6 @@ limitations under the License.
 
 import 'core-js/stable';
 import 'regenerator-runtime/runtime';
-import 'isomorphic-fetch';
 import 'es6-promise/auto';
 
 import './object-is';