Add option to indicate bundle encoding

Summary: public

To improve cold start performance we want to be able to avoid decoding the bundle at all. To make that happen we need to be able to generate a bundle encoded on `ucs2`. This diff adds support for indicating the encoding the Packager should use for bundling.

Reviewed By: davidaurelio

Differential Revision: D2582365

fb-gh-sync-id: 905384272a668910c57a1a2ca6d1b723c39233f8

Author: martinbigio

local-cli/bundle/__tests__/saveBundleAndMap-test.js

@@ -41,10 +41,11 @@ describe('saveBundleAndMap', () => {
     saveBundleAndMap(
       codeWithMap,
       'ios',
-      bundleOutput
+      bundleOutput,
+      'utf8',
     );
 
-    expect(fs.writeFileSync.mock.calls[0]).toEqual([bundleOutput, code]);
+    expect(fs.writeFileSync.mock.calls[0]).toEqual([bundleOutput, code, 'utf8']);
   });
 
   it('should save sourcemaps if required so', () => {
@@ -55,6 +56,7 @@ describe('saveBundleAndMap', () => {
       codeWithMap,
       'ios',
       bundleOutput,
+      'utf8',
       sourceMapOutput
     );
 

local-cli/bundle/buildBundle.js

@@ -49,6 +49,7 @@ function buildBundle(args, config) {
           outputBundle,
           args.platform,
           args['bundle-output'],
+          args['bundle-encoding'],
           args['sourcemap-output'],
           args['assets-dest']
         ));

local-cli/bundle/bundleCommandLineArgs.js

@@ -32,6 +32,11 @@ module.exports = [
     description: 'File name where to store the resulting bundle, ex. /tmp/groups.bundle',
     type: 'string',
     required: true,
+  }, {
+    command: 'bundle-encoding',
+    description: 'Encoding the bundle should be written in (https://nodejs.org/api/buffer.html#buffer_buffer).',
+    type: 'string',
+    default: 'utf8',
   }, {
     command: 'sourcemap-output',
     description: 'File name where to store the sourcemap file for resulting bundle, ex. /tmp/groups.map',

local-cli/bundle/saveBundleAndMap.js

@@ -20,11 +20,12 @@ function saveBundleAndMap(
   codeWithMap,
   platform,
   bundleOutput,
+  encoding,
   sourcemapOutput,
   assetsDest
 ) {
   log('Writing bundle output to:', bundleOutput);
-  fs.writeFileSync(bundleOutput, sign(codeWithMap.code));
+  fs.writeFileSync(bundleOutput, sign(codeWithMap.code), encoding);
   log('Done writing bundle output');
 
   if (sourcemapOutput) {