Parse comma-separated multiple values.

lib/src/arg_parser.dart

Index: lib/src/arg_parser.dart
diff --git a/lib/src/arg_parser.dart b/lib/src/arg_parser.dart
index e7f728c034954593318d4ace2bd5be745b38f6ba..49d6aa6bbf6dc4d7a965536049fd8c305e87006e 100644
--- a/lib/src/arg_parser.dart
+++ b/lib/src/arg_parser.dart
@@ -77,18 +77,25 @@ class ArgParser {
   ///
   /// * There is already an option with name [name].
   /// * There is already an option using abbreviation [abbr].
+  /// * [splitCommas] is passed but [allowMultiple] is `false`.
   void addOption(String name, {String abbr, String help, String valueHelp,
       List<String> allowed, Map<String, String> allowedHelp, String defaultsTo,
-      void callback(value), bool allowMultiple: false, bool hide: false}) {
+      void callback(value), bool allowMultiple: false, bool splitCommas,
+      bool hide: false}) {
+    if (!allowMultiple && splitCommas != null) {
+      throw new ArgumentError(
+          'splitCommas may not be set if allowMultiple is false.');

[Sean Eagan, 2015/03/04 22:28:03]

Why not?  Seems like it would be reasonable that someone would want to allow
e.g.
`--foo=a,b,c`, but not `--foo=a,b --foo=c`.  In fact the latter seems kind of
useless.

[nweiz, 2015/03/04 22:39:55]

Why would you want to forbid the latter? That provides no additional
expressiveness, and is contrary to how many existing command-line tools work.

+    }
+
     _addOption(name, abbr, help, valueHelp, allowed, allowedHelp, defaultsTo,
         callback, allowMultiple ? OptionType.MULTIPLE : OptionType.SINGLE,
-        hide: hide);
+        splitCommas: splitCommas, hide: hide);
   }
 
   void _addOption(String name, String abbr, String help, String valueHelp,
       List<String> allowed, Map<String, String> allowedHelp, defaultsTo,
       void callback(value), OptionType type,
-      {bool negatable: false, bool hide: false}) {
+      {bool negatable: false, bool splitCommas, bool hide: false}) {
     // Make sure the name isn't in use.
     if (_options.containsKey(name)) {
       throw new ArgumentError('Duplicate option "$name".');
@@ -105,7 +112,7 @@ class ArgParser {
 
     _options[name] = newOption(name, abbr, help, valueHelp, allowed,
         allowedHelp, defaultsTo, callback, type,
-        negatable: negatable, hide: hide);
+        negatable: negatable, splitCommas: splitCommas, hide: hide);
   }
 
   /// Parses [args], a list of command-line arguments, matches them against the