Added the ability to get the names of the options in a set of parsed arguments, and the default val…

lib/args/args.dart

Index: lib/args/args.dart
===================================================================
--- lib/args/args.dart	(revision 10607)
+++ lib/args/args.dart	(working copy)
@@ -489,6 +489,14 @@
 
     return null;
   }
+
+  /**
+   * Get the default value for an option. Useful after parsing to test
+   * if the user specified something other than the default.

[Bob Nystrom, 2012/08/16 21:26:58]

This method is useful in its own right, but if it's just for testing that, why
not have isDefault(option) on ArgResults?

[gram, 2012/08/16 21:55:53]

ArgResults does not have that information. We could add a flag but then there
are two choices, neither of which are great - have a second map and duplicate
all the keys, or change the map to contain classes with option data rather than
just values. This seemed like a lightweight approach that has a trivial
implementation and, as you point out, adds more flexibility than just the use
case that drove me to add it. Isn't solving a more general problem considered a
good thing, especially when it comes virtually for free? If we added
isDefault(), and then later on discovered we had other reasons for getting at
the default value, we might end up adding yet another method, and thus is born
needless complexity.

+   */
+
+   getDefault(String option) => _options.containsKey(option) ?
+       _options[option].defaultValue : null;

[Bob Nystrom, 2012/08/16 21:26:58]

If the option name is invalid, this should throw an InvalidArgumentException,
not just silently return null.

[gram, 2012/08/16 21:55:53]

Done. I assume you mean IllegalArgument...

 }
 
 /**
@@ -518,6 +526,9 @@
 
     return _options[name];
   }
+
+  /** Get the names of the options as a [Collection]. */
+  Collection<String> get options => _options.getKeys();

[Bob Nystrom, 2012/08/16 21:26:58]

Instead of this, how about making ArgResults implement Collection itself?

[gram, 2012/08/16 21:55:53]

That seems like a lot of extra effort. All I want is a way to get at the valid
keys for indexing. Would it be enough to  change the name to getKeys()? Or to
implement Iterable<String>? Or leave it as is?

 }
 
 class _Option {