Add subparser aliases for argparse. Resolves issue 9324. Approved by Georg for…

Add subparser aliases for argparse. Resolves issue 9324. Approved by Georg for beta2 on the tracker.

Doc/library/argparse.rst

@@ -1428,6 +1428,16 @@ Sub-commands
 
        {foo,bar}   additional help
 
+   Furthermore, ``add_parser`` supports an additional ``aliases`` argument,
+   which allows multiple strings to refer to the same subparser. This example,
+   like ``svn``, aliases ``co`` as a shorthand for ``checkout``::
+
+     >>> parser = argparse.ArgumentParser()
+     >>> subparsers = parser.add_subparsers()
+     >>> checkout = subparsers.add_parser('checkout', aliases=['co'])
+     >>> checkout.add_argument('foo')
+     >>> parser.parse_args(['co', 'bar'])
+     Namespace(foo='bar')
 
    One particularly effective way of handling sub-commands is to combine the use
    of the :meth:`add_subparsers` method with calls to :meth:`set_defaults` so
@@ -1466,7 +1476,7 @@ Sub-commands
      >>> args.func(args)
      ((XYZYX))
 
-   This way, you can let :meth:`parse_args` does the job of calling the
+   This way, you can let :meth:`parse_args` do the job of calling the
    appropriate function after argument parsing is complete.  Associating
    functions with actions like this is typically the easiest way to handle the
    different actions for each of your subparsers.  However, if it is necessary

Lib/argparse.py

@@ -1023,9 +1023,13 @@ class _SubParsersAction(Action):
 
     class _ChoicesPseudoAction(Action):
 
-        def __init__(self, name, help):
+        def __init__(self, name, aliases, help):
+            metavar = dest = name
+            if aliases:
+                metavar += ' (%s)' % ', '.join(aliases)
             sup = super(_SubParsersAction._ChoicesPseudoAction, self)
-            sup.__init__(option_strings=[], dest=name, help=help)
+            sup.__init__(option_strings=[], dest=dest, help=help,
+                         metavar=metavar)
 
     def __init__(self,
                  option_strings,
@@ -1053,15 +1057,22 @@ class _SubParsersAction(Action):
         if kwargs.get('prog') is None:
             kwargs['prog'] = '%s %s' % (self._prog_prefix, name)
 
+        aliases = kwargs.pop('aliases', ())
+
         # create a pseudo-action to hold the choice help
         if 'help' in kwargs:
             help = kwargs.pop('help')
-            choice_action = self._ChoicesPseudoAction(name, help)
+            choice_action = self._ChoicesPseudoAction(name, aliases, help)
             self._choices_actions.append(choice_action)
 
         # create the parser and add it to the map
         parser = self._parser_class(**kwargs)
         self._name_parser_map[name] = parser
+
+        # make parser available under aliases also
+        for alias in aliases:
+            self._name_parser_map[alias] = parser
+
         return parser
 
     def _get_subactions(self):

Lib/test/test_argparse.py

@@ -1708,7 +1708,8 @@ class TestAddSubparsers(TestCase):
     def assertArgumentParserError(self, *args, **kwargs):
         self.assertRaises(ArgumentParserError, *args, **kwargs)
 
-    def _get_parser(self, subparser_help=False, prefix_chars=None):
+    def _get_parser(self, subparser_help=False, prefix_chars=None,
+                    aliases=False):
         # create a parser with a subparsers argument
         if prefix_chars:
             parser = ErrorRaisingArgumentParser(
@@ -1724,13 +1725,21 @@ class TestAddSubparsers(TestCase):
             'bar', type=float, help='bar help')
 
         # check that only one subparsers argument can be added
-        subparsers = parser.add_subparsers(help='command help')
+        subparsers_kwargs = {}
+        if aliases:
+            subparsers_kwargs['metavar'] = 'COMMAND'
+            subparsers_kwargs['title'] = 'commands'
+        else:
+            subparsers_kwargs['help'] = 'command help'
+        subparsers = parser.add_subparsers(**subparsers_kwargs)
         self.assertArgumentParserError(parser.add_subparsers)
 
         # add first sub-parser
         parser1_kwargs = dict(description='1 description')
         if subparser_help:
             parser1_kwargs['help'] = '1 help'
+        if aliases:
+            parser1_kwargs['aliases'] = ['1alias1', '1alias2']
         parser1 = subparsers.add_parser('1', **parser1_kwargs)
         parser1.add_argument('-w', type=int, help='w help')
         parser1.add_argument('x', choices='abc', help='x help')
@@ -1947,6 +1956,44 @@ class TestAddSubparsers(TestCase):
               -y {1,2,3}  y help
             '''))
 
+    def test_alias_invocation(self):
+        parser = self._get_parser(aliases=True)
+        self.assertEqual(
+            parser.parse_known_args('0.5 1alias1 b'.split()),
+            (NS(foo=False, bar=0.5, w=None, x='b'), []),
+        )
+        self.assertEqual(
+            parser.parse_known_args('0.5 1alias2 b'.split()),
+            (NS(foo=False, bar=0.5, w=None, x='b'), []),
+        )
+
+    def test_error_alias_invocation(self):
+        parser = self._get_parser(aliases=True)
+        self.assertArgumentParserError(parser.parse_args,
+                                       '0.5 1alias3 b'.split())
+
+    def test_alias_help(self):
+        parser = self._get_parser(aliases=True, subparser_help=True)
+        self.maxDiff = None
+        self.assertEqual(parser.format_help(), textwrap.dedent("""\
+            usage: PROG [-h] [--foo] bar COMMAND ...
+
+            main description
+
+            positional arguments:
+              bar                   bar help
+
+            optional arguments:
+              -h, --help            show this help message and exit
+              --foo                 foo help
+
+            commands:
+              COMMAND
+                1 (1alias1, 1alias2)
+                                    1 help
+                2                   2 help
+            """))
+
 # ============
 # Groups tests
 # ============

Misc/ACKS

@@ -734,6 +734,7 @@ Hajime Saitou
 George Sakkis
 Rich Salz
 Kevin Samborn
+Adrian Sampson
 Ilya Sandler
 Mark Sapiro
 Ty Sarna

Misc/NEWS

@@ -84,6 +84,8 @@ Build
 
 - The Windows build now uses Tcl/Tk 8.5.9 and sqlite3 3.7.4.
 
+- Issue #9234: argparse supports alias names for subparsers.
+
 
 What's New in Python 3.2 Beta 1?
 ================================