python · serhiy-storchaka · Sep 24, 2024 · Sep 24, 2024
diff --git a/Lib/argparse.py b/Lib/argparse.py
@@ -1575,9 +1575,8 @@ def _get_positional_kwargs(self, dest, **kwargs):

        # mark positional arguments as required if at least one is
        # always required
-        if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE]:
-            kwargs['required'] = True
-        if kwargs.get('nargs') == ZERO_OR_MORE and 'default' not in kwargs:
+        nargs = kwargs.get('nargs')
+        if nargs not in [OPTIONAL, ZERO_OR_MORE, REMAINDER, SUPPRESS, 0]:
            kwargs['required'] = True

        # return the keyword arguments with no option strings

diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
@@ -3033,7 +3033,7 @@ def get_parser(self, required):
        group = parser.add_mutually_exclusive_group(required=required)
        group.add_argument('--foo', action='store_true', help='FOO')
        group.add_argument('--spam', help='SPAM')
-        group.add_argument('badger', nargs='*', default='X', help='BADGER')
+        group.add_argument('badger', nargs='*', help='BADGER')
        return parser

    failures = [
@@ -3044,13 +3044,13 @@ def get_parser(self, required):
        '--foo X Y',
    ]
    successes = [
-        ('--foo', NS(foo=True, spam=None, badger='X')),
-        ('--spam S', NS(foo=False, spam='S', badger='X')),
+        ('--foo', NS(foo=True, spam=None, badger=[])),
+        ('--spam S', NS(foo=False, spam='S', badger=[])),
        ('X', NS(foo=False, spam=None, badger=['X'])),
        ('X Y Z', NS(foo=False, spam=None, badger=['X', 'Y', 'Z'])),
    ]
    successes_when_not_required = [
-        ('', NS(foo=False, spam=None, badger='X')),
+        ('', NS(foo=False, spam=None, badger=[])),
    ]

    usage_when_not_required = '''\
@@ -6020,7 +6020,28 @@ def test_required_args(self):
        self.parser.add_argument('bar')
        self.parser.add_argument('baz')
        self.assertRaisesRegex(argparse.ArgumentError,
-                               'the following arguments are required: bar, baz',
+                               'the following arguments are required: bar, baz$',
+                               self.parser.parse_args, [])
+
+    def test_required_args_optional(self):
+        self.parser.add_argument('bar')
+        self.parser.add_argument('baz', nargs='?')
+        self.assertRaisesRegex(argparse.ArgumentError,
+                               'the following arguments are required: bar$',
+                               self.parser.parse_args, [])
+
+    def test_required_args_zero_or_more(self):
+        self.parser.add_argument('bar')
+        self.parser.add_argument('baz', nargs='*')
+        self.assertRaisesRegex(argparse.ArgumentError,
+                               'the following arguments are required: bar$',
+                               self.parser.parse_args, [])
+
+    def test_required_args_remainder(self):
+        self.parser.add_argument('bar')
+        self.parser.add_argument('baz', nargs='...')
+        self.assertRaisesRegex(argparse.ArgumentError,
+                               'the following arguments are required: bar$',
                               self.parser.parse_args, [])

    def test_required_mutually_exclusive_args(self):

diff --git a/Misc/NEWS.d/next/Library/2024-09-21-22-32-21.gh-issue-72795.naLmkX.rst b/Misc/NEWS.d/next/Library/2024-09-21-22-32-21.gh-issue-72795.naLmkX.rst
@@ -0,0 +1,4 @@
+Positional arguments with :ref:`nargs` equal to ``'*'`` or
+:data:`!argparse.REMAINDER` are no longer required. This allows to use
+positional argument with ``nargs='*'`` and without ``default`` in mutually
+exclusive group and improves error message about required arguments.