Move all args to per-request for the worker, and add a test

test/worker/worker_test.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:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:bazel_worker/bazel_worker.dart';
 // TODO(jakemac): Remove once this is a part of the testing library.
 import 'package:bazel_worker/src/async_message_grouper.dart';
 import 'package:bazel_worker/testing.dart';
 import 'package:test/test.dart';
 
 main() {
   group('Hello World', () {
+    final argsFile = new File('test/worker/hello_world.args').absolute;
     final inputDartFile = new File('test/worker/hello_world.dart').absolute;
     final outputJsFile = new File('test/worker/hello_world.js').absolute;
-    final executableArgs = [
-      'bin/dartdevc.dart',
-      'compile',
-    ];
+    final executableArgs = ['bin/dartdevc.dart', 'compile',];
     final compilerArgs = [
       '--no-source-map',
       '--no-summarize',
       '-o',
       outputJsFile.path,
       inputDartFile.path,
     ];
 
     setUp(() {
       inputDartFile.createSync();
       inputDartFile.writeAsStringSync('main() => print("hello world");');
     });
 
     tearDown(() {
       if (inputDartFile.existsSync()) inputDartFile.deleteSync();
       if (outputJsFile.existsSync()) outputJsFile.deleteSync();
+      if (argsFile.existsSync()) argsFile.deleteSync();
     });
 
     test('can compile in worker mode', () async {
       var args = new List.from(executableArgs)..add('--persistent_worker');
       var process = await Process.start('dart', args);
       var messageGrouper = new AsyncMessageGrouper(process.stdout);
 
       var request = new WorkRequest();
       request.arguments.addAll(compilerArgs);
       process.stdin.add(protoToDelimitedBuffer(request));
@@ skipping 23 matching lines @@
 
     test('can compile in basic mode', () {
       var args = new List.from(executableArgs)..addAll(compilerArgs);
       var result = Process.runSync('dart', args);
 
       expect(result.exitCode, EXIT_CODE_OK);
       expect(result.stdout, isEmpty);
       expect(result.stderr, isEmpty);
       expect(outputJsFile.existsSync(), isTrue);
     });
+
+    test('can compile in basic mode with args in a file', () async {
+      argsFile.createSync();
+      argsFile.writeAsStringSync(compilerArgs.join('\n'));
+      var args = new List.from(executableArgs)..add('@${argsFile.path}');
+      var process = await Process.start('dart', args);
+      stderr.addStream(process.stderr);
+      var futureProcessOutput = process.stdout.map(UTF8.decode).toList();
+
+      expect(await process.exitCode, EXIT_CODE_OK);
+      expect((await futureProcessOutput).join(), isEmpty);
+      expect(outputJsFile.existsSync(), isTrue);
+    });
   });
 
   group('Hello World with Summaries', () {
     final greetingDart = new File('test/worker/greeting.dart').absolute;
     final helloDart = new File('test/worker/hello.dart').absolute;
 
     final greetingJS = new File('test/worker/greeting.js').absolute;
     final greetingSummary = new File('test/worker/greeting.sum').absolute;
     final helloJS = new File('test/worker/hello_world.js').absolute;
 
@@ skipping 44 matching lines @@
       expect(helloJS.existsSync(), isTrue);
     });
   });
 }
 
 Future<WorkResponse> _readResponse(MessageGrouper messageGrouper) async {
   var buffer = await messageGrouper.next;
   try {
     return new WorkResponse.fromBuffer(buffer);
   } catch (_) {
-    throw 'Failed to parse response: \n'
-        'bytes: $buffer\n'
-        'String: ${new String.fromCharCodes(buffer)}\n';
+    var bufferAsString =
+        buffer == null ? '' : 'String: ${UTF8.decode(buffer)}\n';
+    throw 'Failed to parse response:\nbytes: $buffer\n$bufferAsString';
   }
 }