Output `.meta` files for plain bundles

Summary: Outputs `.meta` files for plain text bundles just like “old packager” did.

Reviewed By: jeanlauliac, cpojer

Differential Revision: D5077649

fbshipit-source-id: eb87999dd899066adeb9756333adb4d79ce04832

packager/src/ModuleGraph/output/as-plain-bundle.js

@@ -10,6 +10,8 @@
  */
 'use strict';
 
+const meta = require('../../../../local-cli/bundle/output/meta');
+
 const {createIndexMap} = require('./source-map');
 const {addModuleIdsToModuleWrapper} = require('./util');
 
@@ -41,7 +43,11 @@ module.exports = (
       code += `/*# sourceMappingURL=${sourceMapPath}*/`;
     }
 
-    return {code, map: createIndexMap({file: filename, sections})};
+    return {
+      code,
+      extraFiles: [[`${filename}.meta`, meta(code)]],
+      map: createIndexMap({file: filename, sections}),
+    };
   }: OutputFn);
 
 const reLine = /^/gm;

packager/src/ModuleGraph/types.flow.js

@@ -78,7 +78,8 @@ export type OutputFn = (
 ) => OutputResult;
 
 type OutputResult = {|
-  code: string,
+  code: string | Buffer,
+  extraFiles: Iterable<[string, string | Buffer]>,
   map: SourceMap,
 |};