Polyfill window.fetch by Default

packages/next/build/polyfills/fetch.js

@@ -0,0 +1 @@
+export default window.fetch

packages/next/build/polyfills/object-assign.js

@@ -0,0 +1 @@
+module.exports = Object.assign

packages/next/build/webpack-config.ts

@@ -17,6 +17,7 @@ import { fileExists } from '../lib/file-exists'
 import { resolveRequest } from '../lib/resolve-request'
 import {
   CLIENT_STATIC_FILES_RUNTIME_MAIN,
+  CLIENT_STATIC_FILES_PATH,
   CLIENT_STATIC_FILES_RUNTIME_WEBPACK,
   REACT_LOADABLE_MANIFEST,
   SERVER_DIRECTORY,
@@ -115,6 +116,11 @@ export default async function getBaseWebpackConfig(
               dev ? `next-dev.js` : 'next.js'
             )
           ),
+        [path.join(
+          CLIENT_STATIC_FILES_PATH,
+          buildId,
+          'polyfill.js'
+        )]: path.join(NEXT_PROJECT_ROOT_DIST_CLIENT, 'polyfill.js'),
       }
     : undefined
 
@@ -163,6 +169,25 @@ export default async function getBaseWebpackConfig(
       next: NEXT_PROJECT_ROOT,
       [PAGES_DIR_ALIAS]: pagesDir,
       [DOT_NEXT_ALIAS]: distDir,
+      ...(!isServer
+        ? {
+            unfetch: path.join(__dirname, 'polyfills', 'fetch.js'),
+            'isomorphic-unfetch': path.join(__dirname, 'polyfills', 'fetch.js'),
+            'whatwg-fetch': path.join(__dirname, 'polyfills', 'fetch.js'),
+            'object-assign': path.join(
+              __dirname,
+              'polyfills',
+              'object-assign.js'
+            ),
+            'object.assign$': path.join(
+              __dirname,
+              'polyfills',
+              'object-assign.js'
+            ),
+            '@babel/runtime-corejs2/core-js/object/assign':
+              'next/dist/build/polyfills/object-assign.js',
+          }
+        : {}),
     },
     mainFields: isServer ? ['main', 'module'] : ['browser', 'module', 'main'],
     plugins: [PnpWebpackPlugin],

packages/next/client/polyfill.js

@@ -0,0 +1,2 @@
+import 'whatwg-fetch'
+Object.assign = require('object.assign/polyfill')()

packages/next/package.json

@@ -102,6 +102,7 @@
     "mini-css-extract-plugin": "0.8.0",
     "mkdirp": "0.5.1",
     "node-fetch": "2.6.0",
+    "object.assign": "4.1.0",
     "ora": "3.4.0",
     "path-to-regexp": "2.1.0",
     "pnp-webpack-plugin": "1.5.0",
@@ -127,7 +128,8 @@
     "webpack": "4.39.0",
     "webpack-dev-middleware": "3.7.0",
     "webpack-hot-middleware": "2.25.0",
-    "webpack-sources": "1.4.3"
+    "webpack-sources": "1.4.3",
+    "whatwg-fetch": "3.0.0"
   },
   "peerDependencies": {
     "react": "^16.6.0",

packages/next/pages/_document.tsx

@@ -757,6 +757,16 @@ export class NextScript extends Component<OriginProps> {
             }}
           />
         ) : null}
+        <script
+          nonce={this.props.nonce}
+          crossOrigin={this.props.crossOrigin || process.crossOrigin}
+          noModule={true}
+          src={
+            assetPrefix +
+            `/_next/static/${buildId}/polyfill.js` +
+            _devOnlyInvalidateCacheQueryString
+          }
+        />
         {page !== '/_error' && pageScript}
         {appScript}
         {staticMarkup ? null : this.getDynamicChunks()}

test/integration/build-stats-output/test/index.test.js

@@ -9,6 +9,6 @@ const appDir = join(__dirname, '../react-site')
 describe('Build Stats Output', () => {
   it('Shows correct package count in output', async () => {
     const { stdout } = await nextBuild(appDir, undefined, { stdout: true })
-    expect(stdout).toMatch(/\/something .*?4/)
+    expect(stdout).toMatch(/\/something .*?2/)
   })
 })

test/integration/defer-scripts/test/index.test.js

@@ -38,13 +38,14 @@ describe('Defer Scripts', () => {
     let missing = false
 
     for (const script of $('script').toArray()) {
-      const { defer, type } = script.attribs
+      const { defer, type, src } = script.attribs
       // application/json doesn't need defer
-      if (type === 'application/json') {
+      if (type === 'application/json' || /polyfill\.js$/.test(src)) {
         continue
       }
 
       if (defer !== '') {
+        console.log(src)
         missing = true
       }
     }

test/integration/size-limit/test/index.test.js

@@ -81,7 +81,7 @@ describe('Production response size', () => {
     )
 
     // These numbers are without gzip compression!
-    expect(responseSizeKilobytes).toBeLessThanOrEqual(221) // Kilobytes
+    expect(responseSizeKilobytes).toBeLessThanOrEqual(225) // Kilobytes
   })
 
   it('should not increase the overall response size of modern build', async () => {

yarn.lock

@@ -10449,7 +10449,7 @@ object-visit@^1.0.0:
   dependencies:
     isobject "^3.0.0"
 
-object.assign@^4.1.0:
+object.assign@4.1.0, object.assign@^4.1.0:
   version "4.1.0"
   resolved "https://registry.yarnpkg.com/object.assign/-/object.assign-4.1.0.tgz#968bf1100d7956bb3ca086f006f846b3bc4008da"
   integrity sha512-exHJeq6kBKj58mqGyTQ9DFvrZC/eR6OwxzoM9YRoGBqrXYonaFyGiFMuc9VZrXf7DarreEwMpurG3dd+CNyW5w==
@@ -15020,7 +15020,7 @@ [email protected]:
   resolved "https://registry.yarnpkg.com/whatwg-fetch/-/whatwg-fetch-2.0.4.tgz#dde6a5df315f9d39991aa17621853d720b85566f"
   integrity sha512-dcQ1GWpOD/eEQ97k66aiEVpNnapVj90/+R+SXTPYGHpYBBypfKJEQjLrvMZ7YXbKm21gXd4NcuxUTjiv1YtLng==
 
-whatwg-fetch@>=0.10.0:
+whatwg-fetch@3.0.0, whatwg-fetch@>=0.10.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/whatwg-fetch/-/whatwg-fetch-3.0.0.tgz#fc804e458cc460009b1a2b966bc8817d2578aefb"
   integrity sha512-9GSJUgz1D4MfyKU7KRqwOjXCXTqWdFNvEr7eUBYchQiVc744mqK/MzXPNR2WsPkmkOa4ywfg8C2n8h+13Bey1Q==