Use "babel-preset-react-native"

Summary:
Rather than specifying Babel plugins in the `.babelrc` packaged with react-native, leverage a Babel preset to define the plugins (https://github.com/exponentjs/babel-preset-react-native).

This allows for a much better user experience for those who want (or need) to override options in their project's `.babelrc`.

Prior to this PR, if a user wanted to use a custom babel-plugin (or a custom set of babel plugins), they'd have either 1) manually override the `.babelrc` in the react-packager directory (or fork RN), or 2) specify a custom transformer to use when running the packager that loaded their own `.babelrc`. Note - the custom transformer was necessary because without it, RN's `.babelrc` options would supersede the options defined in the project's `.babelrc`...potentially causing issues with plugin ordering.

This PR makes the transformer check for the existence of a project-level `.babelrc`, and if it it's there, it _doesn't_ use the react-native `.babelrc`. This prevents any oddities with Babel plug
Closes https://github.com/facebook/react-native/pull/5214

Reviewed By: davidaurelio

Differential Revision: D2881814

Pulled By: martinbigio

fb-gh-sync-id: 4168144b7a365fae62bbeed094d8a03a48b4798c

babelRegisterOnly.js

@@ -16,7 +16,7 @@ var path = require('path');
 var _only = [];
 
 function readBabelRC() {
-  var rcpath = path.join(__dirname, 'react-packager', '.babelrc');
+  var rcpath = path.join(__dirname, 'react-packager', 'rn-babelrc.json');
   var source = fs.readFileSync(rcpath).toString();
   return JSON.parse(source);
 }
@@ -25,5 +25,5 @@ module.exports = function(onlyList) {
   _only = _only.concat(onlyList);
   var config = readBabelRC();
   config.only = _only;
-  require('babel-core/register')(config);
+  require('babel-register')(config);
 };

react-packager/.babelrc

@@ -1,30 +0,0 @@
-{
-  "retainLines": true,
-  "compact": true,
-  "comments": false,
-  "plugins": [
-    "syntax-async-functions",
-    "syntax-class-properties",
-    "syntax-trailing-function-commas",
-    "transform-class-properties",
-    "transform-es2015-arrow-functions",
-    "transform-es2015-block-scoping",
-    "transform-es2015-classes",
-    "transform-es2015-computed-properties",
-    "transform-es2015-constants",
-    "transform-es2015-destructuring",
-    ["transform-es2015-modules-commonjs", {"strict": false, "allowTopLevelThis": true}],
-    "transform-es2015-parameters",
-    "transform-es2015-shorthand-properties",
-    "transform-es2015-spread",
-    "transform-es2015-template-literals",
-    "transform-flow-strip-types",
-    "transform-object-assign",
-    "transform-object-rest-spread",
-    "transform-react-display-name",
-    "transform-react-jsx",
-    "transform-regenerator",
-    "transform-es2015-for-of"
-  ],
-  "sourceMaps": false
-}

react-packager/index.js

@@ -15,7 +15,6 @@ useGracefulFs();
 var debug = require('debug');
 var omit = require('underscore').omit;
 var Activity = require('./src/Activity');
-var Transforms = require('./src/transforms');
 
 exports.createServer = createServer;
 exports.middleware = function(options) {
@@ -24,7 +23,6 @@ exports.middleware = function(options) {
 };
 
 exports.Activity = Activity;
-exports.getTransforms = Transforms.getAll;
 
 // Renamed "package" to "bundle". But maintain backwards
 // compat.

react-packager/rn-babelrc.json

@@ -0,0 +1,4 @@
+{
+  "presets": [ "react-native" ],
+  "plugins": []
+}

react-packager/src/JSTransformer/index.js

@@ -66,6 +66,7 @@ class Transformer {
 
     this._cache = opts.cache;
     this._transformModulePath = opts.transformModulePath;
+    this._projectRoots = opts.projectRoots;
 
     if (opts.transformModulePath != null) {
       let transformer;
@@ -129,6 +130,7 @@ class Transformer {
             filename: filePath,
             options: {
               ...options,
+              projectRoots: this._projectRoots,
               externalTransformModulePath: this._transformModulePath,
             },
           }).then(res => {

react-packager/src/JSTransformer/resolvePlugins.js

@@ -1,32 +0,0 @@
-/**
- * Copyright (c) 2015-present, Facebook, Inc.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- */
-'use strict';
-
-/**
- * Manually resolve all default Babel plugins.
- * `babel.transform` will attempt to resolve all base plugins relative to
- * the file it's compiling. This makes sure that we're using the plugins
- * installed in the react-native package.
- */
-function resolvePlugins(plugins) {
-  return plugins.map(function(plugin) {
-    // Normalise plugin to an array.
-    if (!Array.isArray(plugin)) {
-      plugin = [plugin];
-    }
-    // Only resolve the plugin if it's a string reference.
-    if (typeof plugin[0] === 'string') {
-      plugin[0] = require('babel-plugin-' + plugin[0]);
-      plugin[0] = plugin[0].__esModule ? plugin[0].default : plugin[0];
-    }
-    return plugin;
-  });
-}
-
-module.exports = resolvePlugins;

react-packager/src/JSTransformer/worker.js

@@ -9,30 +9,25 @@
 'use strict';
 
 var babel = require('babel-core');
-var resolvePlugins = require('./resolvePlugins');
-var Transforms = require('../transforms');
+var makeInternalConfig = require('babel-preset-react-native/configs/internal');
 
 // Runs internal transforms on the given sourceCode. Note that internal
 // transforms should be run after the external ones to ensure that they run on
 // Javascript code
 function internalTransforms(sourceCode, filename, options) {
-  var plugins = resolvePlugins(Transforms.getAll(options));
-  if (plugins.length === 0) {
+  var internalBabelConfig = makeInternalConfig(options);
+
+  if (!internalBabelConfig) {
     return {
       code: sourceCode,
       filename: filename,
     };
   }
 
-  var result = babel.transform(sourceCode, {
-    retainLines: true,
-    compact: true,
-    comments: false,
+  var result = babel.transform(sourceCode, Object.assign({
     filename: filename,
     sourceFileName: filename,
-    sourceMaps: false,
-    plugins: plugins,
-  });
+  }, internalBabelConfig));
 
   return {
     code: result.code,

react-packager/src/Resolver/index.js

@@ -93,7 +93,6 @@ class Resolver {
         // should work after this release and we can
         // remove it from here.
         'parse',
-        'react-transform-hmr',
       ],
       platforms: ['ios', 'android'],
       preferNativePlatform: true,

react-packager/src/transforms/index.js

@@ -1,14 +0,0 @@
-/**
- * Copyright (c) 2015-present, Facebook, Inc.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- */
-'use strict';
-
-exports.getAll = function(options) {
-  return [];
-};
-

transformer.js

@@ -11,47 +11,95 @@
 'use strict';
 
 const babel = require('babel-core');
+const externalHelpersPlugin = require('babel-plugin-external-helpers');
 const fs = require('fs');
-const inlineRequires = require('fbjs-scripts/babel-6/inline-requires');
+const makeHMRConfig = require('babel-preset-react-native/configs/hmr');
+const resolvePlugins = require('babel-preset-react-native/lib/resolvePlugins');
+const inlineRequiresPlugin = require('fbjs-scripts/babel-6/inline-requires');
 const json5 = require('json5');
 const path = require('path');
-const ReactPackager = require('./react-packager');
-const resolvePlugins = require('./react-packager/src/JSTransformer/resolvePlugins');
 
-const babelRC =
-  json5.parse(
-    fs.readFileSync(
-      path.resolve(__dirname, 'react-packager', '.babelrc')));
+/**
+ * Return a memoized function that checks for the existence of a
+ * project level .babelrc file, and if it doesn't exist, reads the
+ * default RN babelrc file and uses that.
+ */
+const getBabelRC = (function() {
+  let babelRC = null;
 
-function transform(src, filename, options) {
-  options = options || {};
+  return function _getBabelRC(projectRoots) {
+    if (babelRC !== null) {
+      return babelRC;
+    }
+
+    babelRC = { plugins: [] }; // empty babelrc
+
+    // Let's look for the .babelrc in the first project root.
+    // In the future let's look into adding a command line option to specify
+    // this location.
+    //
+    // NOTE: we're not reading the project's .babelrc here. We leave it up to
+    // Babel to do that automatically and apply the transforms accordingly
+    // (which works because we pass in `filename` and `sourceFilename` to
+    // Babel when we transform).
+    let projectBabelRCPath;
+    if (projectRoots && projectRoots.length > 0) {
+      projectBabelRCPath = path.resolve(projectRoots[0], '.babelrc');
+    }
+
+    // If a .babelrc file doesn't exist in the project,
+    // use the Babel config provided with react-native.
+    if (!projectBabelRCPath || !fs.existsSync(projectBabelRCPath)) {
+      babelRC = json5.parse(
+        fs.readFileSync(
+          path.resolve(__dirname, 'react-packager', 'rn-babelrc.json'))
+        );
+
+      // Require the babel-preset's listed in the default babel config
+      babelRC.presets = babelRC.presets.map((preset) => require('babel-preset-' + preset));
+      babelRC.plugins = resolvePlugins(babelRC.plugins);
+    }
+
+    return babelRC;
+  }
+})();
+
+/**
+ * Given a filename and options, build a Babel
+ * config object with the appropriate plugins.
+ */
+function buildBabelConfig(filename, options) {
+  const babelRC = getBabelRC(options.projectRoots);
 
-  const extraPlugins = ['external-helpers-2'];
   const extraConfig = {
     filename,
     sourceFileName: filename,
   };
 
-  const config = Object.assign({}, babelRC, extraConfig);
-  if (options.hot) {
-    extraPlugins.push([
-      'react-transform',
-      {
-        transforms: [{
-          transform: 'react-transform-hmr/lib/index.js',
-          imports: ['React'],
-          locals: ['module'],
-        }]
-      },
-    ]);
-  }
+  let config = Object.assign({}, babelRC, extraConfig);
+
+  // Add extra plugins
+  const extraPlugins = [externalHelpersPlugin];
 
   if (options.inlineRequires) {
-    extraPlugins.push(inlineRequires);
+    extraPlugins.push(inlineRequiresPlugin);
   }
-  config.plugins = resolvePlugins(extraPlugins.concat(config.plugins));
 
-  const result = babel.transform(src, Object.assign({}, babelRC, config));
+  config.plugins = extraPlugins.concat(config.plugins);
+
+  if (options.hot) {
+    const hmrConfig = makeHMRConfig(options);
+    config = Object.assign({}, config, hmrConfig);
+  }
+
+  return Object.assign({}, babelRC, config);
+}
+
+function transform(src, filename, options) {
+  options = options || {};
+
+  const babelConfig = buildBabelConfig(filename, options);
+  const result = babel.transform(src, babelConfig);
 
   return {
     code: result.code,