refactor: use babel overrides to transpile babel runtime helpers

packages/@vue/babel-preset-app/__tests__/babel-preset.spec.js

@@ -107,7 +107,7 @@ test('async/await', () => {
   // should use regenerator runtime
   expect(code).toMatch(`import "regenerator-runtime/runtime"`)
   // should use required helper instead of inline
-  expect(code).toMatch(/import _asyncToGenerator from ".*runtime-corejs3\/helpers\/esm\/asyncToGenerator\"/)
+  expect(code).toMatch(/import _asyncToGenerator from ".*runtime\/helpers\/esm\/asyncToGenerator\"/)
 })
 
 test('jsx', () => {
@@ -135,7 +135,8 @@ test('jsx options', () => {
       jsx: {
         injectH: false
       }
-    }]]
+    }]],
+    filename: 'test-entry-file.js'
   })
   expect(code).not.toMatch(`var h = arguments[0]`)
   expect(code).toMatch(`return h("div", ["bar"])`)
@@ -152,6 +153,6 @@ test('disable absoluteRuntime', () => {
     filename: 'test-entry-file.js'
   })
 
-  expect(code).toMatch('import _toConsumableArray from "@babel/runtime-corejs3/helpers/esm/toConsumableArray"')
+  expect(code).toMatch('import _toConsumableArray from "@babel/runtime/helpers/esm/toConsumableArray"')
   expect(code).not.toMatch(getAbsolutePolyfill('es.promise'))
 })

packages/@vue/babel-preset-app/index.js

@@ -183,24 +183,25 @@ module.exports = (context, options = {}) => {
     absoluteRuntime
   }])
 
-  // use @babel/runtime-corejs3 so that helpers that need polyfillable APIs will reference core-js instead.
-  // if useBuiltIns is not set to 'usage', then it means users would take care of the polyfills on their own,
-  // i.e., core-js 3 is no longer needed.
-  // this extra plugin can be removed once one of the two issues resolves:
-  // https://github.com/babel/babel/issues/7597
-  // https://github.com/babel/babel/issues/9903
-  if (useBuiltIns === 'usage' && !process.env.VUE_CLI_MODERN_BUILD) {
-    const runtimeCoreJs3Path = path.dirname(require.resolve('@babel/runtime-corejs3/package.json'))
-    plugins.push([require('babel-plugin-module-resolver'), {
-      alias: {
-        '@babel/runtime': '@babel/runtime-corejs3',
-        [runtimePath]: runtimeCoreJs3Path
-      }
-    }])
-  }
-
   return {
-    presets,
-    plugins
+    overrides: [{
+      exclude: [/@babel[\/|\\\\]runtime/, /core-js/],
+      presets,
+      plugins
+    }, {
+      // there are some untranspiled code in @babel/runtime
+      // https://github.com/babel/babel/issues/9903
+      include: [/@babel[\/|\\\\]runtime/],
+      presets: [
+        [require('@babel/preset-env'), {
+          useBuiltIns,
+          corejs: 3
+        }]
+      ]
+    }]
   }
 }
+
+// a special flag to tell @vue/cli-plugin-babel to include @babel/runtime for transpilation
+// otherwise the above `include` option won't take effect
+process.env.VUE_CLI_TRANSPILE_BABEL_RUNTIME = true

packages/@vue/babel-preset-app/package.json

@@ -31,10 +31,8 @@
     "@babel/plugin-transform-runtime": "^7.6.2",
     "@babel/preset-env": "^7.6.3",
     "@babel/runtime": "^7.6.3",
-    "@babel/runtime-corejs3": "^7.6.3",
     "@vue/babel-preset-jsx": "^1.1.1",
     "babel-plugin-dynamic-import-node": "^2.2.0",
-    "babel-plugin-module-resolver": "^3.2.0",
     "core-js": "^3.3.2",
     "core-js-compat": "^3.3.2"
   }

packages/@vue/cli-plugin-babel/__tests__/babel-runtime.spec.js

@@ -0,0 +1,77 @@
+jest.setTimeout(80000)
+
+const { defaultPreset } = require('@vue/cli/lib/options')
+const create = require('@vue/cli-test-utils/createTestProject')
+const serve = require('@vue/cli-test-utils/serveWithPuppeteer')
+
+test('should add polyfills for code in @babel/runtime', async () => {
+  const project = await create('babel-runtime-polyfills', defaultPreset)
+
+  await project.write('src/main.js', `
+  const x = function () {
+    setTimeout(
+      // eslint-disable-next-line
+      () => console.log(...arguments), 100
+    );
+  }
+  x(1, 2)
+  `)
+
+  await project.run('vue-cli-service build --mode development')
+  const vendorFile = await project.read('dist/js/chunk-vendors.js')
+
+  // iterableToArray is used to transform `console.log(...arguments)`
+  expect(vendorFile).toMatch('iterableToArray')
+  // with inline helpers, preset-env can detect the symbol polyfill is required
+  // (because the implementation of `iterableToArray` relies on it)
+  // however, with transform-runtime plugin, helpers are only references to @babel/runtime modules
+  // so we need to make sure polyfill detection is enabled for @babel/runtime too
+  expect(vendorFile).toMatch('es.symbol')
+})
+
+test('should not transpile babel helpers multiple times', async () => {
+  const project = await create('babel-runtime-helpers', defaultPreset)
+
+  const mainjs = await project.read('src/main.js')
+  await project.write('src/main.js', `
+  // eslint-disable-next-line
+  console.log(typeof Symbol('a'))
+
+  ${mainjs}
+  `)
+
+  // if the typeof symbol helper is transpiled recursively,
+  // there would be an error thrown and the page would be empty
+  await serve(
+    () => project.run('vue-cli-service serve'),
+    async ({ helpers }) => {
+      const msg = `Welcome to Your Vue.js App`
+      expect(await helpers.getText('h1')).toMatch(msg)
+    }
+  )
+})
+
+// #4742 core-js-pure imports are likely to be caused by
+// incorrect configuration of @babel/plugin-transform-runtime
+test('should not introduce polyfills from core-js-pure', async () => {
+  const project = await create('babel-runtime-core-js-pure', defaultPreset)
+
+  await project.write('src/main.js', `
+import Vue from 'vue'
+import App from './App.vue'
+
+Vue.config.productionTip = false
+
+new Vue({
+  render: h => h(App),
+  methods: {
+    myfunc: async function () {}
+  }
+}).$mount('#app')
+  `)
+
+  await project.run('vue-cli-service build --mode development')
+  const vendorFile = await project.read('dist/js/chunk-vendors.js')
+
+  expect(vendorFile).not.toMatch('core-js-pure')
+})

packages/@vue/cli-plugin-babel/index.js

@@ -1,4 +1,5 @@
 const path = require('path')
+const babel = require('@babel/core')
 const { isWindows } = require('@vue/cli-shared-utils')
 
 function genTranspileDepRegex (transpileDependencies) {
@@ -17,9 +18,14 @@ function genTranspileDepRegex (transpileDependencies) {
 
 module.exports = (api, options) => {
   const useThreads = process.env.NODE_ENV === 'production' && !!options.parallel
-  const cliServicePath = require('path').dirname(require.resolve('@vue/cli-service'))
+  const cliServicePath = path.dirname(require.resolve('@vue/cli-service'))
   const transpileDepRegex = genTranspileDepRegex(options.transpileDependencies)
 
+  // try to load the project babel config;
+  // if the default preset is used,
+  // there will be a VUE_CLI_TRANSPILE_BABEL_RUNTIME env var set.
+  babel.loadPartialConfig()
+
   api.chainWebpack(webpackConfig => {
     webpackConfig.resolveLoader.modules.prepend(path.join(__dirname, 'node_modules'))
 
@@ -36,6 +42,15 @@ module.exports = (api, options) => {
             if (filepath.startsWith(cliServicePath)) {
               return true
             }
+
+            // only include @babel/runtime when the @vue/babel-preset-app preset is used
+            if (
+              process.env.VUE_CLI_TRANSPILE_BABEL_RUNTIME &&
+              filepath.includes(path.join('@babel', 'runtime'))
+            ) {
+              return false
+            }
+
             // check if this is something the user explicitly wants to transpile
             if (transpileDepRegex && transpileDepRegex.test(filepath)) {
               return false

packages/@vue/cli-service/__tests__/serve.spec.js

@@ -6,6 +6,8 @@ const { defaultPreset } = require('@vue/cli/lib/options')
 const create = require('@vue/cli-test-utils/createTestProject')
 const serve = require('@vue/cli-test-utils/serveWithPuppeteer')
 
+const sleep = n => new Promise(resolve => setTimeout(resolve, n))
+
 test('serve', async () => {
   const project = await create('e2e-serve', defaultPreset)
 
@@ -53,6 +55,7 @@ test('serve with router', async () => {
       expect(await helpers.hasClass('a[href="#/about"]', 'router-link-exact-active')).toBe(false)
 
       await page.click('a[href="#/about"]')
+      await sleep(1000)
       expect(await helpers.getText('h1')).toMatch(`This is an about page`)
       expect(await helpers.hasElement('#nav')).toBe(true)
       expect(await helpers.hasClass('a[href="#/"]', 'router-link-exact-active')).toBe(false)
@@ -76,6 +79,7 @@ test('serve with legacy router option', async () => {
       expect(await helpers.hasClass('a[href="/about"]', 'router-link-exact-active')).toBe(false)
 
       await page.click('a[href="/about"]')
+      await sleep(1000)
       expect(await helpers.getText('h1')).toMatch(`This is an about page`)
       expect(await helpers.hasElement('#nav')).toBe(true)
       expect(await helpers.hasClass('a[href="/"]', 'router-link-exact-active')).toBe(false)