implement ES6 modules in JS AST.

lib/src/options.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Set of flags and options passed to the compiler
 library dev_compiler.src.options;
 
 import 'dart:io';
 
 import 'package:args/args.dart';
@@ skipping 55 matching lines @@
   /// Output directory for generated code.
   final String outputDir;
 
   /// Emit Closure Compiler-friendly code.
   final bool closure;
 
   /// Whether to emit a workaround for missing arrow function bind-this in
   /// other V8 builds
   final bool arrowFnBindThisWorkaround;
 
+  /// Which module format to support.
+  /// Currently 'es6' and 'dart' are supported.
+  final String moduleFormat;
+
   const CodegenOptions(
       {this.emitSourceMaps: true,
       this.forceCompile: false,
       this.closure: _CLOSURE_DEFAULT,
       this.outputDir,
-      this.arrowFnBindThisWorkaround: false});
+      this.arrowFnBindThisWorkaround: false,
+      this.moduleFormat: 'dart'});
 }
 
 /// Options for devrun.
 class RunnerOptions {
   /// V8-based binary to be used to run the .js output (d8, iojs, node).
   /// Can be just the executable name if it's in the path, or a path to the
   /// executable.
   final String v8Binary;
 
   const RunnerOptions({this.v8Binary: _V8_BINARY_DEFAULT});
@@ skipping 128 matching lines @@
   }
 
   if (serverMode && args.rest.length != 1) showUsage = true;
 
   return new CompilerOptions(
       codegenOptions: new CodegenOptions(
           emitSourceMaps: args['source-maps'],
           forceCompile: args['force-compile'] || serverMode,
           closure: args['closure'],
           outputDir: outputDir,
-          arrowFnBindThisWorkaround: args['arrow-fn-bind-this']),
+          arrowFnBindThisWorkaround: args['arrow-fn-bind-this'],
+          moduleFormat: args['modules']),
       sourceOptions: new SourceResolverOptions(
           useMockSdk: args['mock-sdk'],
           dartSdkPath: sdkPath,
           useImplicitHtml: serverMode &&
               args.rest.length == 1 &&
               args.rest[0].endsWith('.dart'),
           customUrlMappings: customUrlMappings,
           useMultiPackage: args['use-multi-package'],
           packageRoot: args['package-root'],
           packagePaths: args['package-paths'].split(','),
@@ skipping 44 matching lines @@
           'look for packages in.',
       defaultsTo: '')
   ..addOption('resources',
       help: 'Additional resources to serve', defaultsTo: '')
   ..addFlag('source-maps',
       help: 'Whether to emit source map files', defaultsTo: true)
   ..addOption('runtime-dir',
       help: 'Where to find dev_compiler\'s runtime files', defaultsTo: null)
   ..addFlag('arrow-fn-bind-this',
       help: 'Work around `this` binding in => functions')
+  ..addOption('modules',
+      help: 'Which module pattern to emit',
+      allowed: ['es6', 'dart'],
+      allowedHelp: {
+        'es6': 'es6 modules',
+        'custom-dart': 'a custom format used by dartdevc, similar to AMD'
+      },
+      defaultsTo: 'dart')
 
   // general options
   ..addFlag('help', abbr: 'h', help: 'Display this message')
   ..addFlag('version',
       negatable: false, help: 'Display the Dev Compiler verion')
   ..addFlag('server', help: 'Run as a development server.', defaultsTo: false)
   ..addFlag('hashing',
       help: 'Enable hash-based file caching.', defaultsTo: null)
   ..addFlag('widget',
       help: 'Serve embedded widget with static errors and warnings.',
@@ skipping 75 matching lines @@
     // The pub-cache directory is two levels up, but we verify that the layout
     // looks correct.
     if (path.basename(dir) != 'dev_compiler') return null;
     dir = path.dirname(dir);
     if (path.basename(dir) != 'global_packages') return null;
     dir = path.dirname(dir);
     return path.join(dir, cacheDir, 'lib', 'runtime');
   }
   return null;
 }