gh-59330: argparse: Properly handle positional arguments containing '-'

Lib/argparse.py

@@ -1350,7 +1350,17 @@ def __eq__(self, other):
         return vars(self) == vars(other)
 
     def __contains__(self, key):
-        return key in self.__dict__
+        return key in self.__dict__ or key.replace('-', '_') in self.__dict__
+
+    def __getattr__(self, name):
+        # Compatibility for people doing getattr(args, 'foo-bar') instead of
+        # args.foo_bar. This might lead to some false positives, but this
+        # is unlikely.
+        try:
+            return self.__dict__[name.replace('-', '_')]
+        except KeyError:
+            msg = "'%s' object has no attribute '%s'"
+            raise AttributeError(msg % (type(self).__name__, name))
 
 
 class _ActionsContainer(object):
@@ -1577,6 +1587,9 @@ def _get_positional_kwargs(self, dest, **kwargs):
         if kwargs.get('nargs') == ZERO_OR_MORE and 'default' not in kwargs:
             kwargs['required'] = True
 
+        # make dest attribute-accessible, 'foo-bar' -> 'foo_bar'
+        dest = dest.replace('-', '_')
+
         # return the keyword arguments with no option strings
         return dict(kwargs, dest=dest, option_strings=[])
 

Lib/test/test_argparse.py

@@ -1348,6 +1348,16 @@ class TestPositionalsNargsOptionalOneOrMore(ParserTestCase):
     ]
 
 
+class TestPositionalDest(ParserTestCase):
+    """Tests setting destination"""
+
+    argument_signatures = [Sig("foo-bar")]
+    failures = []
+    successes = [
+        ("biz", NS(foo_bar="biz")),
+    ]
+
+
 class TestPositionalsChoicesString(ParserTestCase):
     """Test a set of single-character choices"""
 

Misc/NEWS.d/next/Core and Builtins/2023-05-03-15-29-03.gh-issue-59330.ywvw4w.rst

@@ -0,0 +1 @@
+Hyphens in positional arguments in argparse module are automatically replaced with underscores. Patch by Simon Law and Furkan Onder.