Add .wasParsed() to ArgResults.

pkg/args/lib/args.dart

Index: pkg/args/lib/args.dart
diff --git a/pkg/args/lib/args.dart b/pkg/args/lib/args.dart
index ec40958991bc5a1a497cd26a652a0ead28016051..e14c9d37d4b52b3ea5aedcdd5c898e7d86fe576d 100644
--- a/pkg/args/lib/args.dart
+++ b/pkg/args/lib/args.dart
@@ -69,7 +69,7 @@ class ArgParser {
   void addFlag(String name, {String abbr, String help, bool defaultsTo: false,
       bool negatable: true, void callback(bool value), bool hide: false}) {
     _addOption(name, abbr, help, null, null, null, defaultsTo, callback,
-        isFlag: true, negatable: negatable, hide: hide);
+        OptionType.FLAG, negatable: negatable, hide: hide);
   }
 
   /// Defines a value-taking option. Throws an [ArgumentError] if:
@@ -80,14 +80,14 @@ class ArgParser {
       List<String> allowed, Map<String, String> allowedHelp, String defaultsTo,
       void callback(value), bool allowMultiple: false, bool hide: false}) {
     _addOption(name, abbr, help, valueHelp, allowed, allowedHelp, defaultsTo,
-        callback, isFlag: false, allowMultiple: allowMultiple,
+        callback, allowMultiple ? OptionType.MULTIPLE : OptionType.SINGLE,
         hide: hide);
   }
 
   void _addOption(String name, String abbr, String help, String valueHelp,
       List<String> allowed, Map<String, String> allowedHelp, defaultsTo,
-      void callback(value), {bool isFlag, bool negatable: false,
-      bool allowMultiple: false, bool hide: false}) {
+      void callback(value), OptionType type, {bool negatable: false,
+      bool hide: false}) {
     // Make sure the name isn't in use.
     if (_options.containsKey(name)) {
       throw new ArgumentError('Duplicate option "$name".');
@@ -103,8 +103,8 @@ class ArgParser {
     }
 
     _options[name] = new Option(name, abbr, help, valueHelp, allowed,
-        allowedHelp, defaultsTo, callback, isFlag: isFlag, negatable: negatable,
-        allowMultiple: allowMultiple, hide: hide);
+        allowedHelp, defaultsTo, callback, type, negatable: negatable,
+        hide: hide);
   }
 
   /// Parses [args], a list of command-line arguments, matches them against the
@@ -140,7 +140,11 @@ class ArgParser {
 /// Includes the parsed options and any remaining unparsed command line
 /// arguments.
 class ArgResults {
-  final Map<String, dynamic> _options;
+  /// The [ArgParser] whose options were parsed for these results.
+  final ArgParser _parser;
+
+  /// The option values that were parsed from arguments.
+  final Map<String, dynamic> _parsed;
 
   /// If these are the results for parsing a command's options, this will be the
   /// name of the command. For top-level results, this returns `null`.
@@ -160,20 +164,46 @@ class ArgResults {
   final List<String> rest;
 
   /// Creates a new [ArgResults].
-  ArgResults(this._options, this.name, this.command, List<String> rest)
-    : this.rest = new UnmodifiableListView(rest);
+  ArgResults(this._parser, this._parsed, this.name, this.command,
+      List<String> rest)
+      : this.rest = new UnmodifiableListView(rest);
 
   /// Gets the parsed command-line option named [name].
   operator [](String name) {
-    if (!_options.containsKey(name)) {
-      throw new ArgumentError(
-          'Could not find an option named "$name".');
+    if (!_parser.options.containsKey(name)) {
+      throw new ArgumentError('Could not find an option named "$name".');
     }
 
-    return _options[name];
+    return _parser.options[name].getOrDefault(_parsed[name]);
   }
 
-  /// Get the names of the options as an [Iterable].
-  Iterable<String> get options => _options.keys;
+  /// Get the names of the available options as an [Iterable].
+  ///
+  /// This includes the options whose values were parsed or that have defaults.
+  /// Options that weren't present and have no default will be omitted.
+  Iterable<String> get options {
+    var result = new Set.from(_parsed.keys);
+
+    // Include the options that have defaults.
+    _parser.options.forEach((name, option) {
+      if (option.defaultValue != null) result.add(name);
+    });
+
+    return result;
+  }
+
+  /// Returns `true` if the option with [name] was parsed from an actual
+  /// argument.
+  ///
+  /// Returns `false` if it wasn't provided and the default value or no default
+  /// value would be used instead.
+  bool wasParsed(String name) {
+    var option = _parser.options[name];
+    if (option == null) {
+      throw new ArgumentError('Could not find an option named "$name".');
+    }
+
+    return _parsed.containsKey(name);
+  }
 }