Polyfill missing std lib fns for module browsers

packages/next-polyfill-module/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "@next/polyfill-module",
+  "version": "9.5.4-canary.16",
+  "description": "A standard library polyfill for ES Modules supporting browsers (Edge 16+, Firefox 60+, Chrome 61+, Safari 10.1+)",
+  "main": "dist/polyfill-module.js",
+  "license": "MIT",
+  "repository": {
+    "url": "vercel/next.js",
+    "directory": "packages/next-polyfill-module"
+  },
+  "scripts": {
+    "prepublish": "microbundle src/index.js -f iife --no-sourcemap --external none",
+    "build": "microbundle watch src/index.js -f iife --no-sourcemap --external none"
+  },
+  "devDependencies": {
+    "microbundle": "0.11.0"
+  }
+}

packages/next-polyfill-module/src/index.js

@@ -0,0 +1,94 @@
+/* eslint-disable no-extend-native */
+
+// Contains polyfills for methods missing after browser version(s):
+// Edge 16, Firefox 60, Chrome 61, Safari 10.1
+
+/**
+ * Available in:
+ * Edge: never
+ * Firefox: 61
+ * Chrome: 66
+ * Safari: 12
+ *
+ * https://caniuse.com/mdn-javascript_builtins_string_trimstart
+ * https://caniuse.com/mdn-javascript_builtins_string_trimend
+ */
+if (!('trimStart' in String.prototype)) {
+  String.prototype.trimStart = String.prototype.trimLeft
+}
+if (!('trimEnd' in String.prototype)) {
+  String.prototype.trimEnd = String.prototype.trimRight
+}
+
+/**
+ * Available in:
+ * Edge: never
+ * Firefox: 63
+ * Chrome: 70
+ * Safari: 12.1
+ *
+ * https://caniuse.com/mdn-javascript_builtins_symbol_description
+ */
+if (!('description' in Symbol.prototype)) {
+  Object.defineProperty(Symbol.prototype, 'description', {
+    get: function get() {
+      return /\((.+)\)/.exec(this)[1]
+    },
+  })
+}
+
+/**
+ * Available in:
+ * Edge: never
+ * Firefox: 62
+ * Chrome: 69
+ * Safari: 12
+ *
+ * https://caniuse.com/array-flat
+ */
+// Copied from https://gist.github.com/developit/50364079cf0390a73e745e513fa912d9
+// Licensed Apache-2.0
+if (!Array.prototype.flat) {
+  Array.prototype.flat = function flat(d, c) {
+    return (
+      (c = this.concat.apply([], this)),
+      d > 1 && c.some(Array.isArray) ? c.flat(d - 1) : c
+    )
+  }
+  Array.prototype.flatMap = function (c, a) {
+    return this.map(c, a).flat()
+  }
+}
+
+/**
+ * Available in:
+ * Edge: 18
+ * Firefox: 58
+ * Chrome: 63
+ * Safari: 11.1
+ *
+ * https://caniuse.com/promise-finally
+ */
+// Modified from https://gist.github.com/developit/e96097d9b657f2a2f3e588ffde433437
+// Licensed Apache-2.0
+if (!Promise.prototype.finally) {
+  Promise.prototype.finally = function (callback) {
+    if (typeof callback !== 'function') {
+      return this.then(callback, callback)
+    }
+
+    var P = this.constructor || Promise
+    return this.then(
+      function (value) {
+        return P.resolve(callback()).then(function () {
+          return value
+        })
+      },
+      function (err) {
+        return P.resolve(callback()).then(function () {
+          throw err
+        })
+      }
+    )
+  }
+}

packages/next/client/index.tsx

@@ -1,21 +1,22 @@
 /* global location */
+import '@next/polyfill-module'
 import React from 'react'
 import ReactDOM from 'react-dom'
 import { HeadManagerContext } from '../next-server/lib/head-manager-context'
 import mitt from '../next-server/lib/mitt'
 import { RouterContext } from '../next-server/lib/router-context'
-import { delBasePath, hasBasePath } from '../next-server/lib/router/router'
 import type Router from '../next-server/lib/router/router'
 import type {
   AppComponent,
   AppProps,
   PrivateRouteInfo,
 } from '../next-server/lib/router/router'
+import { delBasePath, hasBasePath } from '../next-server/lib/router/router'
 import { isDynamicRoute } from '../next-server/lib/router/utils/is-dynamic'
 import * as querystring from '../next-server/lib/router/utils/querystring'
 import * as envConfig from '../next-server/lib/runtime-config'
-import { getURL, loadGetInitialProps, ST } from '../next-server/lib/utils'
 import type { NEXT_DATA } from '../next-server/lib/utils'
+import { getURL, loadGetInitialProps, ST } from '../next-server/lib/utils'
 import initHeadManager from './head-manager'
 import PageLoader, { looseToArray, StyleSheetTuple } from './page-loader'
 import measureWebVitals from './performance-relayer'
@@ -41,10 +42,6 @@ declare global {
 type RenderRouteInfo = PrivateRouteInfo & { App: AppComponent }
 type RenderErrorProps = Omit<RenderRouteInfo, 'Component' | 'styleSheets'>
 
-if (!('finally' in Promise.prototype)) {
-  ;(Promise.prototype as PromiseConstructor['prototype']).finally = require('next/dist/build/polyfills/finally-polyfill.min')
-}
-
 const data: typeof window['__NEXT_DATA__'] = JSON.parse(
   document.getElementById('__NEXT_DATA__')!.textContent!
 )

packages/next/package.json

@@ -76,6 +76,7 @@
     "@babel/preset-typescript": "7.10.4",
     "@babel/runtime": "7.11.2",
     "@babel/types": "7.11.5",
+    "@next/polyfill-module": "9.5.4-canary.16",
     "@next/react-dev-overlay": "9.5.4-canary.16",
     "@next/react-refresh-utils": "9.5.4-canary.16",
     "ast-types": "0.13.2",
@@ -179,7 +180,6 @@
     "escape-string-regexp": "2.0.0",
     "etag": "1.8.1",
     "file-loader": "6.0.0",
-    "finally-polyfill": "0.1.0",
     "find-up": "4.1.0",
     "fresh": "0.5.2",
     "gzip-size": "5.1.1",

packages/next/taskfile.js

@@ -11,26 +11,14 @@ export async function next__polyfill_nomodule(task, opts) {
     .target('dist/build/polyfills')
 }
 
-export async function finally_polyfill(task, opts) {
-  await task
-    .source(
-      opts.src || relative(__dirname, require.resolve('finally-polyfill'))
-    )
-    .target('dist/build/polyfills')
-}
-
 export async function unfetch(task, opts) {
   await task
     .source(opts.src || relative(__dirname, require.resolve('unfetch')))
     .target('dist/build/polyfills')
 }
 
 export async function browser_polyfills(task) {
-  await task.parallel([
-    'next__polyfill_nomodule',
-    'finally_polyfill',
-    'unfetch',
-  ])
+  await task.parallel(['next__polyfill_nomodule', 'unfetch'])
 }
 
 const externals = {

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

@@ -94,17 +94,17 @@ describe('Build Output', () => {
       expect(parseFloat(indexSize) - 265).toBeLessThanOrEqual(0)
       expect(indexSize.endsWith('B')).toBe(true)
 
-      // should be no bigger than 60.2 kb
-      expect(parseFloat(indexFirstLoad) - 60.5).toBeLessThanOrEqual(0)
+      // should be no bigger than 60.8 kb
+      expect(parseFloat(indexFirstLoad) - 60.8).toBeLessThanOrEqual(0)
       expect(indexFirstLoad.endsWith('kB')).toBe(true)
 
       expect(parseFloat(err404Size) - 3.5).toBeLessThanOrEqual(0)
       expect(err404Size.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(err404FirstLoad) - 63.7).toBeLessThanOrEqual(0)
+      expect(parseFloat(err404FirstLoad) - 63.8).toBeLessThanOrEqual(0)
       expect(err404FirstLoad.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(sharedByAll) - 60.2).toBeLessThanOrEqual(0)
+      expect(parseFloat(sharedByAll) - 60.4).toBeLessThanOrEqual(0)
       expect(sharedByAll.endsWith('kB')).toBe(true)
 
       if (_appSize.endsWith('kB')) {

yarn.lock

@@ -7545,11 +7545,6 @@ finalhandler@~1.1.2:
     statuses "~1.5.0"
     unpipe "~1.0.0"
 
-finally-polyfill@0.1.0:
-  version "0.1.0"
-  resolved "https://registry.yarnpkg.com/finally-polyfill/-/finally-polyfill-0.1.0.tgz#2a17b16581d9477db16a703c7b79a898ac0b7d50"
-  integrity sha512-J1LEcZ5VXe1l3sEO+S//WqL5wcJ/ep7QeKJA6HhNZrcEEFj0eyC8IW3DEZhxySI2bx3r85dwAXz+vYPGuHx5UA==
-
 find-cache-dir@3.3.1, find-cache-dir@^3.0.0, find-cache-dir@^3.3.1:
   version "3.3.1"
   resolved "https://registry.yarnpkg.com/find-cache-dir/-/find-cache-dir-3.3.1.tgz#89b33fad4a4670daa94f855f7fbe31d6d84fe880"