Using arg parsing lib for dart2js.

lib/compiler/implementation/dart2js.dart

 // Copyright (c) 2012, 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.
 
 #library('dart2js');
 
 #import('dart:io');
 #import('dart:uri');
 #import('dart:utf');
 
+#import('../../args/args.dart');
 #import('../compiler.dart', prefix: 'api');
 #import('colors.dart', prefix: 'colors');
 #import('source_file.dart');
 #import('filenames.dart');
 #import('util/uri_extras.dart');
 
 final String LIBRARY_ROOT = '../../../..';
 
-void compile(List<String> argv) {
+ArgResults parseCommandLine(List<String> argv) {
+  // Set up and parse the command line arguments.
+  ArgParser parser = new ArgParser(usage: 'dart2js [options...] <dart file>');
+  parser.addFlag('throw-on-error',
+      help: 'Throw an exception if a fatal error occurs.');
+  parser.addFlag('suppress-warnings',
+      help: 'Display static warnings');
+  parser.addFlag('verbose', abbr: 'v',
+      help: 'Display verbose output');
+  parser.addFlag('allow-mock-compilation');
+  parser.addFlag('colors', defaultsTo: true,
+      help: 'Use color when displaying output');
+  parser.addOption('library-root',
+      help: 'Path to core lib directory');
+  parser.addOption('out', abbr: 'o',
+      help: 'Output JavaScript file to create',
+      defaultsTo: 'out.js');
+
+  return parser.process(argv);
+}
+
+void compile(ArgResults args) {
+  colors.enabled = args['colors'];
+  bool throwOnError = args['throw-on-error'];
+  bool showWarnings = !args['suppress-warnings'];
+  bool verbose = args['verbose'];
+
   Uri cwd = getCurrentDirectory();
-  bool throwOnError = false;
-  bool showWarnings = true;
-  bool verbose = false;
   Uri libraryRoot = cwd;
-  Uri out = cwd.resolve('out.js');
+  if (args['library-root'] != null) {
+    String path = nativeToUriPath(args['library-root']);
+    if (!path.endsWith("/")) path = "$path/";
+    libraryRoot = cwd.resolve(path);
+  }
+
+  Uri out = cwd.resolve(args['out']);
+
   List<String> options = new List<String>();
+  if (args['allow-mock-compilation']) {
+    options.add('--allow-mock-compilation');
+  }
 
-  List<String> arguments = <String>[];
-  for (String argument in argv) {
-    if ('--throw-on-error' == argument) {
-      throwOnError = true;
-    } else if ('--suppress-warnings' == argument) {
-      showWarnings = false;
-    } else if ('--verbose' == argument) {
-      verbose = true;
-    } else if (argument.startsWith('--library-root=')) {
-      String path =
-          nativeToUriPath(argument.substring(argument.indexOf('=') + 1));
-      if (!path.endsWith("/")) path = "$path/";
-      libraryRoot = cwd.resolve(path);
-    } else if (argument.startsWith('--out=')) {
-      String path =
-          nativeToUriPath(argument.substring(argument.indexOf('=') + 1));
-      out = cwd.resolve(path);
-    } else if ('--allow-mock-compilation' == argument) {
-      options.add(argument);
-    } else if ('--no-colors' == argument) {
-      colors.enabled = false;
-    } else if ('--enable-checked-mode' == argument) {
-      options.add(argument);
-    } else if (argument.startsWith('-')) {
-      fail('Unknown option $argument.');
-    } else {
-      arguments.add(nativeToUriPath(argument));
-    }
-  }
+  List<String> arguments = args.rest.map(nativeToUriPath);
+
   if (arguments.isEmpty()) {
     fail('No file to compile.');
   }
+
   if (arguments.length > 1) {
     var extra = arguments.getRange(1, arguments.length - 1);
     fail('Extra arguments: $extra.');
   }
 
   Map<String, SourceFile> sourceFiles = <SourceFile>{};
   int dartBytesRead = 0;
 
   Future<String> provider(Uri uri) {
     if (uri.scheme != 'file') {
@@ skipping 68 matching lines @@
 
 void fail(String message) {
   print(message);
   exit(1);
 }
 
 void compilerMain(Options options) {
   var root = uriPathToNative("/$LIBRARY_ROOT");
   List<String> argv = ['--library-root=${options.script}$root'];
   argv.addAll(options.arguments);
-  compile(argv);
+  ArgResults results = parseCommandLine(argv);
+  compile(results);
 }
 
 void main() {
   try {
     compilerMain(new Options());
   } catch (var exception, var trace) {
     try {
       print('Internal error: $exception');
     } catch (var ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }