Merge.

1 files changed, 38 insertions, 5 deletions

diff --git a/Lib/argparse.py b/Lib/argparse.py
index de3cd11479..79f1fe5a6b 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -71,6 +71,7 @@ __all__ = [
     'ArgumentDefaultsHelpFormatter',
     'RawDescriptionHelpFormatter',
     'RawTextHelpFormatter',
+    'MetavarTypeHelpFormatter',
     'Namespace',
     'Action',
     'ONE_OR_MORE',
@@ -82,6 +83,7 @@ __all__ = [
 ]
 
 
+import collections as _collections
 import copy as _copy
 import os as _os
 import re as _re
@@ -422,7 +424,8 @@ class HelpFormatter(object):
 
             # produce all arg strings
             elif not action.option_strings:
-                part = self._format_args(action, action.dest)
+                default = self._get_default_metavar_for_positional(action)
+                part = self._format_args(action, default)
 
                 # if it's in a group, strip the outer []
                 if action in group_actions:
@@ -444,7 +447,7 @@ class HelpFormatter(object):
                 # if the Optional takes a value, format is:
                 #    -s ARGS or --long ARGS
                 else:
-                    default = action.dest.upper()
+                    default = self._get_default_metavar_for_optional(action)
                     args_string = self._format_args(action, default)
                     part = '%s %s' % (option_string, args_string)
 
@@ -530,7 +533,8 @@ class HelpFormatter(object):
 
     def _format_action_invocation(self, action):
         if not action.option_strings:
-            metavar, = self._metavar_formatter(action, action.dest)(1)
+            default = self._get_default_metavar_for_positional(action)
+            metavar, = self._metavar_formatter(action, default)(1)
             return metavar
 
         else:
@@ -544,7 +548,7 @@ class HelpFormatter(object):
             # if the Optional takes a value, format is:
             #    -s ARGS, --long ARGS
             else:
-                default = action.dest.upper()
+                default = self._get_default_metavar_for_optional(action)
                 args_string = self._format_args(action, default)
                 for option_string in action.option_strings:
                     parts.append('%s %s' % (option_string, args_string))
@@ -622,6 +626,12 @@ class HelpFormatter(object):
     def _get_help_string(self, action):
         return action.help
 
+    def _get_default_metavar_for_optional(self, action):
+        return action.dest.upper()
+
+    def _get_default_metavar_for_positional(self, action):
+        return action.dest
+
 
 class RawDescriptionHelpFormatter(HelpFormatter):
     """Help message formatter which retains any formatting in descriptions.
@@ -662,6 +672,22 @@ class ArgumentDefaultsHelpFormatter(HelpFormatter):
         return help
 
 
+class MetavarTypeHelpFormatter(HelpFormatter):
+    """Help message formatter which uses the argument 'type' as the default
+    metavar value (instead of the argument 'dest')
+
+    Only the name of this class is considered a public API. All the methods
+    provided by the class are considered an implementation detail.
+    """
+
+    def _get_default_metavar_for_optional(self, action):
+        return action.type.__name__
+
+    def _get_default_metavar_for_positional(self, action):
+        return action.type.__name__
+
+
+
 # =====================
 # Options and Arguments
 # =====================
@@ -1041,7 +1067,7 @@ class _SubParsersAction(Action):
 
         self._prog_prefix = prog
         self._parser_class = parser_class
-        self._name_parser_map = {}
+        self._name_parser_map = _collections.OrderedDict()
         self._choices_actions = []
 
         super(_SubParsersAction, self).__init__(
@@ -1294,6 +1320,13 @@ class _ActionsContainer(object):
         if not _callable(type_func):
             raise ValueError('%r is not callable' % type_func)
 
+        # raise an error if the metavar does not match the type
+        if hasattr(self, "_get_formatter"):
+            try:
+                self._get_formatter()._format_args(action, None)
+            except TypeError:
+                raise ValueError("length of metavar tuple does not match nargs")
+
         return self._add_action(action)
 
     def add_argument_group(self, *args, **kwargs):