Add a Configuration class that encapsulates command-line configuration.

lib/src/runner/configuration.dart

Index: lib/src/runner/configuration.dart
diff --git a/lib/src/runner/configuration.dart b/lib/src/runner/configuration.dart
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+++ b/lib/src/runner/configuration.dart
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+// Copyright (c) 2015, 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 test.runner.configuration;
+
+import 'dart:io';
+import 'dart:math' as math;
+
+import 'package:args/args.dart';
+import 'package:path/path.dart' as p;
+
+import '../backend/test_platform.dart';
+import '../util/io.dart';
+
+/// The default number of test suites to run at once.
+///
+/// This defaults to half the available processors, since presumably some of
+/// them will be used for the OS and other processes.
+final _defaultConcurrency = math.max(1, Platform.numberOfProcessors ~/ 2);
+
+/// A class that encapsulates the command-line configuration of the test runner.
+class Configuration {
+  /// The parser used to parse the command-line arguments.
+  static final ArgParser _parser = (() {
+    var parser = new ArgParser(allowTrailingOptions: true);
+
+    var allPlatforms = TestPlatform.all.toList();
+    if (!Platform.isMacOS) allPlatforms.remove(TestPlatform.safari);
+    if (!Platform.isWindows) allPlatforms.remove(TestPlatform.internetExplorer);
+
+    parser.addFlag("help", abbr: "h", negatable: false,
+        help: "Shows this usage information.");
+    parser.addFlag("version", negatable: false,
+        help: "Shows the package's version.");
+    parser.addOption("package-root", hide: true);
+    parser.addOption("name",
+        abbr: 'n',
+        help: 'A substring of the name of the test to run.\n'
+            'Regular expression syntax is supported.');
+    parser.addOption("plain-name",
+        abbr: 'N',
+        help: 'A plain-text substring of the name of the test to run.');
+    parser.addOption("platform",
+        abbr: 'p',
+        help: 'The platform(s) on which to run the tests.',
+        allowed: allPlatforms.map((platform) => platform.identifier).toList(),
+        defaultsTo: 'vm',
+        allowMultiple: true);
+    parser.addOption("concurrency",
+        abbr: 'j',
+        help: 'The number of concurrent test suites run.\n'
+            '(defaults to $_defaultConcurrency)',
+        valueHelp: 'threads');
+    parser.addOption("pub-serve",
+        help: 'The port of a pub serve instance serving "test/".',
+        hide: !supportsPubServe,
+        valueHelp: 'port');
+    parser.addOption("reporter",
+        abbr: 'r',
+        help: 'The runner used to print test results.',
+        allowed: ['compact', 'expanded'],
+        defaultsTo: Platform.isWindows ? 'expanded' : 'compact',
+        allowedHelp: {
+      'compact': 'A single line, updated continuously.',
+      'expanded': 'A separate line for each update.'
+    });
+    parser.addFlag("verbose-trace", negatable: false,
+        help: 'Whether to emit stack traces with core library frames.');
+    parser.addFlag("js-trace", negatable: false,
+        help: 'Whether to emit raw JavaScript stack traces for browser tests.');
+    parser.addFlag("color", defaultsTo: null,
+        help: 'Whether to use terminal colors.\n(auto-detected by default)');
+
+    return parser;
+  })();
+
+  /// The usage string for the command-line arguments.
+  static String get usage => _parser.usage;
+
+  /// The results of parsing the arguments.
+  final ArgResults _options;
+
+  /// Whether `--help` was passed.
+  bool get help => _options['help'];
+
+  /// Whether `--version` was passed.
+  bool get version => _options['version'];
+
+  /// Whether stack traces should be presented as-is or folded to remove
+  /// irrelevant packages.
+  bool get verboseTrace => _options['verbose-trace'];
+
+  /// Whether JavaScript stack traces should be left as-is or converted to
+  /// Dart-like traces.
+  bool get jsTrace => _options['js-trace'];
+
+  /// The package root for resolving "package:" URLs.
+  String get packageRoot => _options['package-root'] == null
+      ? p.join(p.current, 'packages')
+      : _options['package-root'];
+
+  /// The name of the reporter to use to display results.
+  String get reporter => _options['reporter'];
+
+  /// The URL for the `pub serve` instance from which to load tests, or `null`
+  /// if tests should be loaded from the filesystem.
+  Uri get pubServeUrl {
+    if (_options['pub-serve'] == null) return null;
+    return Uri.parse("http://localhost:${_options['pub-serve']}");
+  }
+
+  /// Whether to use command-line color escapes.
+  bool get color =>
+      _options["color"] == null ? canUseSpecialChars : _options["color"];
+
+  /// How many tests to run concurrently.
+  int get concurrency => _concurrency;
+  int _concurrency;
+
+  /// The from which to load tests.
+  List<String> get paths => _options.rest.isEmpty ? ["test"] : _options.rest;
+
+  /// Whether the load paths were passed explicitly or the default was used.
+  bool get explicitPaths => _options.rest.isNotEmpty;
+
+  /// The pattern to match against test names to decide which to run, or `null`
+  /// if all tests should be run.
+  Pattern get pattern {
+    if (_options["name"] != null) {
+      return new RegExp(_options["name"]);
+    } else if (_options["plain-name"] != null) {
+      return _options["plain-name"];
+    } else {
+      return null;
+    }
+  }
+
+  /// The set of platforms on which to run tests.
+  List<TestPlatform> get platforms =>
+      _options["platform"].map(TestPlatform.find).toList();
+
+  /// Parses the configuration from [args].
+  ///
+  /// Throws a [FormatException] if [args] are invalid.
+  Configuration.parse(List<String> args)
+      : _options = _parser.parse(args) {
+    _concurrency = _options['concurrency'] == null
+        ? _defaultConcurrency
+        : _wrapFormatException('concurrency', int.parse);
+
+    if (_options["name"] != null && _options["plain-name"] != null) {
+      throw new FormatException(
+          "--name and --plain-name may not both be passed.");
+    }
+  }
+
+  /// Runs [parse] on the value of the option [name], and wraps any
+  /// [FormatException] it throws with additional information.
+  _wrapFormatException(String name, parse(value)) {
+    try {
+      return parse(_options[name]);
+    } on FormatException catch (error) {
+      throw new FormatException('Couldn\'t parse --$name "${_options[name]}": '
+          '${error.message}');
+    }
+  }
+}