Use new JSX transform with React 17 (facebook#9645)

Author: iansu

packages/babel-preset-react-app/create.js

@@ -54,6 +54,10 @@ module.exports = function (api, opts, env) {
     );
   }
 
+  var hasJsxRuntime = Boolean(
+    api.caller(caller => !!caller && caller.hasJsxRuntime)
+  );
+
   if (!isEnvDevelopment && !isEnvProduction && !isEnvTest) {
     throw new Error(
       'Using `babel-preset-react-app` requires that you specify `NODE_ENV` or ' +
@@ -95,7 +99,8 @@ module.exports = function (api, opts, env) {
           development: isEnvDevelopment || isEnvTest,
           // Will use the native built-in instead of trying to polyfill
           // behavior for any plugins that require one.
-          useBuiltIns: true,
+          ...(!hasJsxRuntime ? { useBuiltIns: true } : {}),
+          runtime: opts.runtime || 'classic',
         },
       ],
       isTypeScriptEnabled && [require('@babel/preset-typescript').default],

packages/react-scripts/config/webpack.config.js

@@ -14,6 +14,7 @@ const fs = require('fs');
 const path = require('path');
 const webpack = require('webpack');
 const resolve = require('resolve');
+const semver = require('semver');
 const PnpWebpackPlugin = require('pnp-webpack-plugin');
 const HtmlWebpackPlugin = require('html-webpack-plugin');
 const CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
@@ -35,6 +36,7 @@ const ModuleNotFoundPlugin = require('react-dev-utils/ModuleNotFoundPlugin');
 const ForkTsCheckerWebpackPlugin = require('react-dev-utils/ForkTsCheckerWebpackPlugin');
 const typescriptFormatter = require('react-dev-utils/typescriptFormatter');
 const ReactRefreshWebpackPlugin = require('@pmmmwh/react-refresh-webpack-plugin');
+const react = require(require.resolve('react', { paths: [paths.appPath] }));
 // @remove-on-eject-begin
 const getCacheIdentifier = require('react-dev-utils/getCacheIdentifier');
 // @remove-on-eject-end
@@ -402,7 +404,16 @@ module.exports = function (webpackEnv) {
                 // @remove-on-eject-begin
                 babelrc: false,
                 configFile: false,
-                presets: [require.resolve('babel-preset-react-app')],
+                presets: [
+                  [
+                    require.resolve('babel-preset-react-app'),
+                    {
+                      runtime: semver.gte(react.version, '17.0.0-alpha.0')
+                      ? 'automatic'
+                      : 'classic',
+                    },
+                  ],
+                ],
                 // Make sure we have a unique cache identifier, erring on the
                 // side of caution.
                 // We remove this when the user ejects because the default