Issue #12713: reverted fix pending further discussion.

2 files changed, 32 insertions, 83 deletions

diff --git a/Lib/argparse.py b/Lib/argparse.py
index e0edad8..209b4e9 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1110,12 +1110,6 @@ class _SubParsersAction(Action):
         parser_name = values[0]
         arg_strings = values[1:]
 
-        # get full parser_name from (optional) abbreviated one
-        for p in self._name_parser_map:
-            if p.startswith(parser_name):
-                parser_name = p
-                break
-
         # set the parser name if requested
         if self.dest is not SUPPRESS:
             setattr(namespace, self.dest, parser_name)
@@ -2313,18 +2307,11 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
 
     def _check_value(self, action, value):
         # converted value must be one of the choices (if specified)
-        if action.choices is not None:
-            ac = [ax for ax in action.choices if str(ax).startswith(str(value))]
-            if len(ac) == 0:
-                args = {'value': value,
-                        'choices': ', '.join(map(repr, action.choices))}
-                msg = _('invalid choice: %(value)r (choose from %(choices)s)')
-                raise ArgumentError(action, msg % args)
-            elif len(ac) > 1:
-                args = {'value': value,
-                        'choices': ', '.join(ac)}
-                msg = _('ambiguous choice: %(value)r could match %(choices)s')
-                raise ArgumentError(action, msg % args)
+        if action.choices is not None and value not in action.choices:
+            args = {'value': value,
+                    'choices': ', '.join(map(repr, action.choices))}
+            msg = _('invalid choice: %(value)r (choose from %(choices)s)')
+            raise ArgumentError(action, msg % args)
 
     # =======================
     # Help-formatting methods
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 32d1b0c..52c6247 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -1842,22 +1842,6 @@ class TestAddSubparsers(TestCase):
         parser3.add_argument('t', type=int, help='t help')
         parser3.add_argument('u', nargs='...', help='u help')
 
-        # add fourth sub-parser (to test abbreviations)
-        parser4_kwargs = dict(description='lost description')
-        if subparser_help:
-            parser4_kwargs['help'] = 'lost help'
-        parser4 = subparsers.add_parser('lost', **parser4_kwargs)
-        parser4.add_argument('-w', type=int, help='w help')
-        parser4.add_argument('x', choices='abc', help='x help')
-
-        # add fifth sub-parser, with longer name (to test abbreviations)
-        parser5_kwargs = dict(description='long description')
-        if subparser_help:
-            parser5_kwargs['help'] = 'long help'
-        parser5 = subparsers.add_parser('long', **parser5_kwargs)
-        parser5.add_argument('-w', type=int, help='w help')
-        parser5.add_argument('x', choices='abc', help='x help')
-
         # return the main parser
         return parser
 
@@ -1873,24 +1857,6 @@ class TestAddSubparsers(TestCase):
             args = args_str.split()
             self.assertArgumentParserError(self.parser.parse_args, args)
 
-    def test_parse_args_abbreviation(self):
-        # check some non-failure cases:
-        self.assertEqual(
-            self.parser.parse_args('0.5 long b -w 7'.split()),
-            NS(foo=False, bar=0.5, w=7, x='b'),
-        )
-        self.assertEqual(
-            self.parser.parse_args('0.5 lon b -w 7'.split()),
-            NS(foo=False, bar=0.5, w=7, x='b'),
-        )
-        self.assertEqual(
-            self.parser.parse_args('0.5 los b -w 7'.split()),
-            NS(foo=False, bar=0.5, w=7, x='b'),
-        )
-        # check a failure case: 'lo' is ambiguous
-        self.assertArgumentParserError(self.parser.parse_args,
-                                       '0.5 lo b -w 7'.split())
-
     def test_parse_args(self):
         # check some non-failure cases:
         self.assertEqual(
@@ -1943,80 +1909,78 @@ class TestAddSubparsers(TestCase):
 
     def test_help(self):
         self.assertEqual(self.parser.format_usage(),
-                         'usage: PROG [-h] [--foo] bar {1,2,3,lost,long} ...\n')
+                         'usage: PROG [-h] [--foo] bar {1,2,3} ...\n')
         self.assertEqual(self.parser.format_help(), textwrap.dedent('''\
-            usage: PROG [-h] [--foo] bar {1,2,3,lost,long} ...
+            usage: PROG [-h] [--foo] bar {1,2,3} ...
 
             main description
 
             positional arguments:
-              bar                bar help
-              {1,2,3,lost,long}  command help
+              bar         bar help
+              {1,2,3}     command help
 
             optional arguments:
-              -h, --help         show this help message and exit
-              --foo              foo help
+              -h, --help  show this help message and exit
+              --foo       foo help
             '''))
 
     def test_help_extra_prefix_chars(self):
         # Make sure - is still used for help if it is a non-first prefix char
         parser = self._get_parser(prefix_chars='+:-')
         self.assertEqual(parser.format_usage(),
-                         'usage: PROG [-h] [++foo] bar {1,2,3,lost,long} ...\n')
+                         'usage: PROG [-h] [++foo] bar {1,2,3} ...\n')
         self.assertEqual(parser.format_help(), textwrap.dedent('''\
-            usage: PROG [-h] [++foo] bar {1,2,3,lost,long} ...
+            usage: PROG [-h] [++foo] bar {1,2,3} ...
 
             main description
 
             positional arguments:
-              bar                bar help
-              {1,2,3,lost,long}  command help
+              bar         bar help
+              {1,2,3}     command help
 
             optional arguments:
-              -h, --help         show this help message and exit
-              ++foo              foo help
+              -h, --help  show this help message and exit
+              ++foo       foo help
             '''))
 
 
     def test_help_alternate_prefix_chars(self):
         parser = self._get_parser(prefix_chars='+:/')
         self.assertEqual(parser.format_usage(),
-                         'usage: PROG [+h] [++foo] bar {1,2,3,lost,long} ...\n')
+                         'usage: PROG [+h] [++foo] bar {1,2,3} ...\n')
         self.assertEqual(parser.format_help(), textwrap.dedent('''\
-            usage: PROG [+h] [++foo] bar {1,2,3,lost,long} ...
+            usage: PROG [+h] [++foo] bar {1,2,3} ...
 
             main description
 
             positional arguments:
-              bar                bar help
-              {1,2,3,lost,long}  command help
+              bar         bar help
+              {1,2,3}     command help
 
             optional arguments:
-              +h, ++help         show this help message and exit
-              ++foo              foo help
+              +h, ++help  show this help message and exit
+              ++foo       foo help
             '''))
 
     def test_parser_command_help(self):
         self.assertEqual(self.command_help_parser.format_usage(),
-                         'usage: PROG [-h] [--foo] bar {1,2,3,lost,long} ...\n')
+                         'usage: PROG [-h] [--foo] bar {1,2,3} ...\n')
         self.assertEqual(self.command_help_parser.format_help(),
                          textwrap.dedent('''\
-            usage: PROG [-h] [--foo] bar {1,2,3,lost,long} ...
+            usage: PROG [-h] [--foo] bar {1,2,3} ...
 
             main description
 
             positional arguments:
-              bar                bar help
-              {1,2,3,lost,long}  command help
-                1                1 help
-                2                2 help
-                3                3 help
-                lost             lost help
-                long             long help
+              bar         bar help
+              {1,2,3}     command help
+                1         1 help
+                2         2 help
+                3         3 help
 
             optional arguments:
-              -h, --help         show this help message and exit
-              --foo              foo help
+              -h, --help  show this help message and exit
+              --foo       foo help
             '''))
 
     def test_subparser_title_help(self):
@@ -2119,8 +2083,6 @@ class TestAddSubparsers(TestCase):
                                     1 help
                 2                   2 help
                 3                   3 help
-                lost                lost help
-                long                long help
             """))
 
 # ============