refactor DDC to support --ignore-unrecognized-flags

pkg/dev_compiler/lib/src/compiler/command.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:io';
 import 'package:analyzer/src/command_line/arguments.dart'
-    show extractDefinedVariables;
+    show
+        extractDefinedVariables,
+        filterUnknownArguments,
+        ignoreUnrecognizedFlagsFlag;
 import 'package:analyzer/src/generated/source.dart' show Source;
 import 'package:analyzer/src/summary/package_bundle_reader.dart'
     show InSummarySource;
 import 'package:args/args.dart' show ArgParser, ArgResults;
 import 'package:args/command_runner.dart' show UsageException;
 import 'package:path/path.dart' as path;
 
 import '../analyzer/context.dart' show AnalyzerOptions;
 import 'compiler.dart' show BuildUnit, CompilerOptions, ModuleCompiler;
 import 'module_builder.dart';
 
 bool _verbose = false;
 
 /// Runs a single compile for dartdevc.
 ///
 /// This handles argument parsing, usage, error handling.
 /// See bin/dartdevc.dart for the actual entry point, which includes Bazel
 /// worker support.
 int compile(List<String> args, {void printFn(Object obj)}) {
   printFn ??= print;
   ArgResults argResults;
   var declaredVars = <String, String>{};
   try {
     args = extractDefinedVariables(args, declaredVars);
-    argResults = _argParser().parse(args);
+    var parser = _argParser();
+    if (args.contains('--$ignoreUnrecognizedFlagsFlag')) {
+      args = filterUnknownArguments(args, parser);
+    }
+    argResults = parser.parse(args);
     _verbose = argResults['verbose'];
   } on FormatException catch (error) {
     printFn('$error\n\n$_usageMessage');
     return 64;
   }
   try {
     _compile(argResults, declaredVars, printFn);
     return 0;
   } on UsageException catch (error) {
     // Incorrect usage, input file not found, etc.
@@ skipping 27 matching lines @@
 }
 
 ArgParser _argParser({bool hide: true}) {
   var argParser = new ArgParser(allowTrailingOptions: true)
     ..addFlag('help',
         abbr: 'h',
         help: 'Display this message.\n'
             'Add --verbose to show hidden options.',
         negatable: false)
     ..addFlag('verbose', abbr: 'v', help: 'Verbose output.')
+    ..addFlag(ignoreUnrecognizedFlagsFlag,
+        help: 'Ignore unrecognized command line flags.',
+        defaultsTo: false,
+        negatable: false)
     ..addOption('out',
         abbr: 'o', allowMultiple: true, help: 'Output file (required).')
     ..addOption('module-root',
         help: 'Root module directory.\n'
             'Generated module paths are relative to this root.')
     ..addOption('library-root',
         help: 'Root of source files.\n'
             'Generated library names are relative to this root.');
   addModuleFormatOptions(argParser, allowMultiple: true, hide: hide);
   AnalyzerOptions.addArguments(argParser, hide: hide);
@@ skipping 124 matching lines @@
     '\n\n${_argParser(hide: !_verbose).usage}';
 
 void _usageException(String message) {
   throw new UsageException(message, _usageMessage);
 }
 
 /// Thrown when the input source code has errors.
 class CompileErrorException implements Exception {
   toString() => '\nPlease fix all errors before compiling (warnings are okay).';
 }