gh-58573: Fix conflicts between abbreviated long options in the parent parser and subparsers in argparse (GH-124631)

Check for ambiguous options if the option is consumed, not when it is
parsed.

Lib/argparse.py

@@ -1928,11 +1928,11 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
             # otherwise, add the arg to the arg strings
             # and note the index if it was an option
             else:
-                option_tuple = self._parse_optional(arg_string)
+                option_tuples = self._parse_optional(arg_string)
-                if option_tuple is None:
+                if option_tuples is None:
                     pattern = 'A'
                 else:
-                    option_string_indices[i] = option_tuple
+                    option_string_indices[i] = option_tuples
                     pattern = 'O'
                 arg_string_pattern_parts.append(pattern)
 
@@ -1967,8 +1967,16 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         def consume_optional(start_index):
 
             # get the optional identified at this index
-            option_tuple = option_string_indices[start_index]
+            option_tuples = option_string_indices[start_index]
-            action, option_string, sep, explicit_arg = option_tuple
+            # if multiple actions match, the option string was ambiguous
+            if len(option_tuples) > 1:
+                options = ', '.join([option_string
+                    for action, option_string, sep, explicit_arg in option_tuples])
+                args = {'option': arg_string, 'matches': options}
+                msg = _('ambiguous option: %(option)s could match %(matches)s')
+                raise ArgumentError(None, msg % args)
+
+            action, option_string, sep, explicit_arg = option_tuples[0]
 
             # identify additional optionals in the same arg string
             # (e.g. -xyz is the same as -x -y -z if no args are required)
@@ -2254,7 +2262,7 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         # if the option string is present in the parser, return the action
         if arg_string in self._option_string_actions:
             action = self._option_string_actions[arg_string]
-            return action, arg_string, None, None
+            return [(action, arg_string, None, None)]
 
         # if it's just a single character, it was meant to be positional
         if len(arg_string) == 1:
@@ -2264,25 +2272,14 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         option_string, sep, explicit_arg = arg_string.partition('=')
         if sep and option_string in self._option_string_actions:
             action = self._option_string_actions[option_string]
-            return action, option_string, sep, explicit_arg
+            return [(action, option_string, sep, explicit_arg)]
 
         # search through all possible prefixes of the option string
         # and all actions in the parser for possible interpretations
         option_tuples = self._get_option_tuples(arg_string)
 
-        # if multiple actions match, the option string was ambiguous
+        if option_tuples:
-        if len(option_tuples) > 1:
+            return option_tuples
-            options = ', '.join([option_string
-                for action, option_string, sep, explicit_arg in option_tuples])
-            args = {'option': arg_string, 'matches': options}
-            msg = _('ambiguous option: %(option)s could match %(matches)s')
-            raise ArgumentError(None, msg % args)
-
-        # if exactly one action matched, this segmentation is good,
-        # so return the parsed action
-        elif len(option_tuples) == 1:
-            option_tuple, = option_tuples
-            return option_tuple
 
         # if it was not found as an option, but it looks like a negative
         # number, it was meant to be positional
@@ -2297,7 +2294,7 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
 
         # it was meant to be an optional but there is no such option
         # in this parser (though it might be a valid option in a subparser)
-        return None, arg_string, None, None
+        return [(None, arg_string, None, None)]
 
     def _get_option_tuples(self, option_string):
         result = []
@@ -2347,43 +2344,40 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         # in all examples below, we have to allow for '--' args
         # which are represented as '-' in the pattern
         nargs = action.nargs
+        # if this is an optional action, -- is not allowed
+        option = action.option_strings
 
         # the default (None) is assumed to be a single argument
         if nargs is None:
-            nargs_pattern = '(-*A-*)'
+            nargs_pattern = '([A])' if option else '(-*A-*)'
 
         # allow zero or one arguments
         elif nargs == OPTIONAL:
-            nargs_pattern = '(-*A?-*)'
+            nargs_pattern = '(A?)' if option else '(-*A?-*)'
 
         # allow zero or more arguments
         elif nargs == ZERO_OR_MORE:
-            nargs_pattern = '(-*[A-]*)'
+            nargs_pattern = '(A*)' if option else '(-*[A-]*)'
 
         # allow one or more arguments
         elif nargs == ONE_OR_MORE:
-            nargs_pattern = '(-*A[A-]*)'
+            nargs_pattern = '(A+)' if option else '(-*A[A-]*)'
 
         # allow any number of options or arguments
         elif nargs == REMAINDER:
-            nargs_pattern = '([-AO]*)'
+            nargs_pattern = '([AO]*)' if option else '(.*)'
 
         # allow one argument followed by any number of options or arguments
         elif nargs == PARSER:
-            nargs_pattern = '(-*A[-AO]*)'
+            nargs_pattern = '(A[AO]*)' if option else '(-*A[-AO]*)'
 
         # suppress action, like nargs=0
         elif nargs == SUPPRESS:
-            nargs_pattern = '(-*-*)'
+            nargs_pattern = '()' if option else '(-*)'
 
         # all others should be integers
         else:
-            nargs_pattern = '(-*%s-*)' % '-*'.join('A' * nargs)
+            nargs_pattern = '([AO]{%d})' % nargs if option else '((?:-*A){%d}-*)' % nargs
-
-        # if this is an optional action, -- is not allowed
-        if action.option_strings:
-            nargs_pattern = nargs_pattern.replace('-*', '')
-            nargs_pattern = nargs_pattern.replace('-', '')
 
         # return the pattern
         return nargs_pattern

Lib/test/test_argparse.py

@@ -2356,6 +2356,28 @@ class TestAddSubparsers(TestCase):
         self.assertEqual(C.w, 7)
         self.assertEqual(C.x, 'b')
 
+    def test_abbreviation(self):
+        parser = ErrorRaisingArgumentParser()
+        parser.add_argument('--foodle')
+        parser.add_argument('--foonly')
+        subparsers = parser.add_subparsers()
+        parser1 = subparsers.add_parser('bar')
+        parser1.add_argument('--fo')
+        parser1.add_argument('--foonew')
+
+        self.assertEqual(parser.parse_args(['--food', 'baz', 'bar']),
+                         NS(foodle='baz', foonly=None, fo=None, foonew=None))
+        self.assertEqual(parser.parse_args(['--foon', 'baz', 'bar']),
+                         NS(foodle=None, foonly='baz', fo=None, foonew=None))
+        self.assertArgumentParserError(parser.parse_args, ['--fo', 'baz', 'bar'])
+        self.assertEqual(parser.parse_args(['bar', '--fo', 'baz']),
+                         NS(foodle=None, foonly=None, fo='baz', foonew=None))
+        self.assertEqual(parser.parse_args(['bar', '--foo', 'baz']),
+                         NS(foodle=None, foonly=None, fo=None, foonew='baz'))
+        self.assertEqual(parser.parse_args(['bar', '--foon', 'baz']),
+                         NS(foodle=None, foonly=None, fo=None, foonew='baz'))
+        self.assertArgumentParserError(parser.parse_args, ['bar', '--food', 'baz'])
+
     def test_parse_known_args_with_single_dash_option(self):
         parser = ErrorRaisingArgumentParser()
         parser.add_argument('-k', '--known', action='count', default=0)

Misc/NEWS.d/next/Library/2024-09-26-22-14-12.gh-issue-58573.hozbm9.rst

@@ -0,0 +1,2 @@
+Fix conflicts between abbreviated long options in the parent parser and
+subparsers in :mod:`argparse`.