move CommandLineParser into analyzer for reuse by DDC

pkg/analyzer/lib/src/command_line/command_line_parser.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 'package:args/args.dart';
+
+/**
+ * Commandline argument parser.
+ *
+ * TODO(pq): when the args package supports ignoring unrecognized options/flags,
+ * this class can be replaced with a simple [ArgParser] instance.
+ */
+class CommandLineParser {
+  static const String IGNORE_UNRECOGNIZED_FLAG = 'ignore-unrecognized-flags';
+
+  final List<String> _knownFlags;
+  final bool _alwaysIgnoreUnrecognized;
+  final ArgParser _parser;
+
+  /// Creates a new command line parser.
+  CommandLineParser({bool alwaysIgnoreUnrecognized: false})
+      : _knownFlags = <String>[],
+        _alwaysIgnoreUnrecognized = alwaysIgnoreUnrecognized,
+        _parser = new ArgParser(allowTrailingOptions: true) {
+    addFlag(IGNORE_UNRECOGNIZED_FLAG,
+        help: 'Ignore unrecognized command line flags.',
+        defaultsTo: false,
+        negatable: false);
+  }
+
+  ArgParser get parser => _parser;
+
+  /// Defines a flag.
+  /// See [ArgParser.addFlag()].
+  void addFlag(String name,
+      {String abbr,
+      String help,
+      bool defaultsTo: false,
+      bool negatable: true,
+      void callback(bool value),
+      bool hide: false}) {
+    _knownFlags.add(name);
+    _parser.addFlag(name,
+        abbr: abbr,
+        help: help,
+        defaultsTo: defaultsTo,
+        negatable: negatable,
+        callback: callback,
+        hide: hide);
+  }
+
+  /// Defines a value-taking option.
+  /// See [ArgParser.addOption()].
+  void addOption(String name,
+      {String abbr,
+      String help,
+      List<String> allowed,
+      Map<String, String> allowedHelp,
+      String defaultsTo,
+      void callback(value),
+      bool allowMultiple: false,
+      bool splitCommas,
+      bool hide: false}) {
+    _knownFlags.add(name);
+    _parser.addOption(name,
+        abbr: abbr,
+        help: help,
+        allowed: allowed,
+        allowedHelp: allowedHelp,
+        defaultsTo: defaultsTo,
+        callback: callback,
+        allowMultiple: allowMultiple,
+        splitCommas: splitCommas,
+        hide: hide);
+  }
+
+  /// Parses [args], a list of command-line arguments, matches them against the
+  /// flags and options defined by this parser, and returns the result.
+  /// See [ArgParser].
+  ArgResults parse(List<String> args) => _parser.parse(_filterUnknowns(args));
+
+  List<String> _filterUnknowns(List<String> args) {
+    if (!_alwaysIgnoreUnrecognized &&
+        !args.contains('--$IGNORE_UNRECOGNIZED_FLAG')) {
+      return args;
+    }
+
+    //TODO(pquitslund): replace w/ the following once library skew issues are
+    // sorted out
+    //return args.where((arg) => !arg.startsWith('--') ||
+    //  _knownFlags.contains(arg.substring(2)));
+
+    // Filter all unrecognized flags and options.
+    List<String> filtered = <String>[];
+    for (int i = 0; i < args.length; ++i) {
+      String arg = args[i];
+      if (arg.startsWith('--') && arg.length > 2) {
+        String option = arg.substring(2);
+        // strip the last '=value'
+        int equalsOffset = option.lastIndexOf('=');
+        if (equalsOffset != -1) {
+          option = option.substring(0, equalsOffset);
+        }
+        // Check the option
+        if (!_knownFlags.contains(option)) {
+          //"eat" params by advancing to the next flag/option
+          i = _getNextFlagIndex(args, i);
+        } else {
+          filtered.add(arg);
+        }
+      } else {
+        filtered.add(arg);
+      }
+    }
+
+    return filtered;
+  }
+
+  int _getNextFlagIndex(args, i) {
+    for (; i < args.length; ++i) {
+      if (args[i].startsWith('--')) {
+        return i;
+      }
+    }
+    return i;
+  }
+}