refactor: remove usage of deprecated babel functions, preparing for babel 8 (#5133)

* refactor: use babel.loadPartialConfigSync (added in babel 7.8)

As planned in https://github.com/babel/babel/issues/10746,
in babel 8 the old `loadPartialConfig` can't be used synchronously.

* refactor: remove dependence on internal babel files, preparing for babel 8

See
https://github.com/babel/babel/issues/10746
https://github.com/babel/babel/pull/10899

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

@@ -14,17 +14,16 @@ const defaultPolyfills = [
 ]
 
 function getPolyfills (targets, includes, { ignoreBrowserslistConfig, configPath }) {
-  const { isPluginRequired } = require('@babel/preset-env')
-  const builtInsList = require('core-js-compat/data')
-  const getTargets = require('@babel/preset-env/lib/targets-parser').default
-  const builtInTargets = getTargets(targets, {
-    ignoreBrowserslistConfig,
-    configPath
-  })
+  const getTargets = require('@babel/helper-compilation-targets').default
+  const builtInTargets = getTargets(targets, { ignoreBrowserslistConfig, configPath })
 
-  return includes.filter(item => {
-    return isPluginRequired(builtInTargets, builtInsList[item])
-  })
+  // if no targets specified, include all default polyfills
+  if (!targets && !Object.keys(builtInTargets).length) {
+    return includes
+  }
+
+  const { list } = require('core-js-compat')({ targets: builtInTargets })
+  return includes.filter(item => list.includes(item))
 }
 
 module.exports = (context, options = {}) => {

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

@@ -23,6 +23,7 @@
   "homepage": "https://github.com/vuejs/vue-cli/tree/dev/packages/@vue/babel-preset-app#readme",
   "dependencies": {
     "@babel/core": "^7.8.4",
+    "@babel/helper-compilation-targets": "^7.8.4",
     "@babel/helper-module-imports": "^7.8.3",
     "@babel/plugin-proposal-class-properties": "^7.8.3",
     "@babel/plugin-proposal-decorators": "^7.8.3",

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

@@ -26,7 +26,7 @@ module.exports = (api, options) => {
   // there will be a VUE_CLI_TRANSPILE_BABEL_RUNTIME env var set.
   // the `filename` field is required
   // in case there're filename-related options like `ignore` in the user config
-  babel.loadPartialConfig({ filename: api.resolve('src/main.js') })
+  babel.loadPartialConfigSync({ filename: api.resolve('src/main.js') })
 
   api.chainWebpack(webpackConfig => {
     webpackConfig.resolveLoader.modules.prepend(path.join(__dirname, 'node_modules'))