1 files changed, 78 insertions, 2 deletions
diff --git a/cliff/_argparse.py b/cliff/_argparse.py
index e48dc79..5358e72 100644
--- a/cliff/_argparse.py
+++ b/cliff/_argparse.py
@@ -14,11 +14,14 @@
 
 from __future__ import absolute_import
 from argparse import *  # noqa
+import argparse
 import sys
+import warnings
 
 
-if sys.version_info < (3, 5):
-    class ArgumentParser(ArgumentParser):  # noqa
+class ArgumentParser(argparse.ArgumentParser):
+
+    if sys.version_info < (3, 5):
         def __init__(self, *args, **kwargs):
             self.allow_abbrev = kwargs.pop("allow_abbrev", True)
             super(ArgumentParser, self).__init__(*args, **kwargs)
@@ -28,3 +31,76 @@ if sys.version_info < (3, 5):
                 return super(ArgumentParser, self)._get_option_tuples(
                     option_string)
             return ()
+
+    # NOTE(dhellmann): We have to override the methods for creating
+    # groups to return our objects that know how to deal with the
+    # special conflict handler.
+
+    def add_argument_group(self, *args, **kwargs):
+        group = _ArgumentGroup(self, *args, **kwargs)
+        self._action_groups.append(group)
+        return group
+
+    def add_mutually_exclusive_group(self, **kwargs):
+        group = _MutuallyExclusiveGroup(self, **kwargs)
+        self._mutually_exclusive_groups.append(group)
+        return group
+
+    def _handle_conflict_ignore(self, action, conflicting_actions):
+        _handle_conflict_ignore(
+            self,
+            self._option_string_actions,
+            action,
+            conflicting_actions,
+        )
+
+
+def _handle_conflict_ignore(container, option_string_actions,
+                            new_action, conflicting_actions):
+
+    # Remember the option strings the new action starts with so we can
+    # restore them as part of error reporting if we need to.
+    original_option_strings = new_action.option_strings
+
+    # Remove all of the conflicting option strings from the new action
+    # and report an error if none are left at the end.
+    for option_string, action in conflicting_actions:
+
+        # remove the conflicting option from the new action
+        new_action.option_strings.remove(option_string)
+        warnings.warn(
+            ('Ignoring option string {} for new action '
+             'because it conflicts with an existing option.').format(
+                 option_string))
+
+        # if the option now has no option string, remove it from the
+        # container holding it
+        if not new_action.option_strings:
+            new_action.option_strings = original_option_strings
+            raise argparse.ArgumentError(
+                new_action,
+                ('Cannot resolve conflicting option string, '
+                 'all names conflict.'),
+            )
+
+
+class _ArgumentGroup(argparse._ArgumentGroup):
+
+    def _handle_conflict_ignore(self, action, conflicting_actions):
+        _handle_conflict_ignore(
+            self,
+            self._option_string_actions,
+            action,
+            conflicting_actions,
+        )
+
+
+class _MutuallyExclusiveGroup(argparse._MutuallyExclusiveGroup):
+
+    def _handle_conflict_ignore(self, action, conflicting_actions):
+        _handle_conflict_ignore(
+            self,
+            self._option_string_actions,
+            action,
+            conflicting_actions,
+        )