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bpo-45235: Fix argparse overrides namespace with subparser defaults (GH-28420)
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3 files changed

+15
-6
lines changed

3 files changed

+15
-6
lines changed

Lib/argparse.py

Lines changed: 7 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1209,7 +1209,8 @@ def __call__(self, parser, namespace, values, option_string=None):
12091209
# namespace for the relevant parts.
12101210
subnamespace, arg_strings = parser.parse_known_args(arg_strings, None)
12111211
for key, value in vars(subnamespace).items():
1212-
setattr(namespace, key, value)
1212+
if not hasattr(namespace, key):
1213+
setattr(namespace, key, value)
12131214

12141215
if arg_strings:
12151216
vars(namespace).setdefault(_UNRECOGNIZED_ARGS_ATTR, [])
@@ -1843,11 +1844,6 @@ def parse_known_args(self, args=None, namespace=None):
18431844
if action.default is not SUPPRESS:
18441845
setattr(namespace, action.dest, action.default)
18451846

1846-
# add any parser defaults that aren't present
1847-
for dest in self._defaults:
1848-
if not hasattr(namespace, dest):
1849-
setattr(namespace, dest, self._defaults[dest])
1850-
18511847
# parse the arguments and exit if there are any errors
18521848
if self.exit_on_error:
18531849
try:
@@ -1858,6 +1854,11 @@ def parse_known_args(self, args=None, namespace=None):
18581854
else:
18591855
namespace, args = self._parse_known_args(args, namespace)
18601856

1857+
# add any parser defaults that aren't present
1858+
for dest in self._defaults:
1859+
if not hasattr(namespace, dest):
1860+
setattr(namespace, dest, self._defaults[dest])
1861+
18611862
if hasattr(namespace, _UNRECOGNIZED_ARGS_ATTR):
18621863
args.extend(getattr(namespace, _UNRECOGNIZED_ARGS_ATTR))
18631864
delattr(namespace, _UNRECOGNIZED_ARGS_ATTR)

Lib/test/test_argparse.py

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3079,6 +3079,12 @@ def test_set_defaults_on_parent_and_subparser(self):
30793079
xparser.set_defaults(foo=2)
30803080
self.assertEqual(NS(foo=2), parser.parse_args(['X']))
30813081

3082+
def test_set_defaults_on_subparser_with_namespace(self):
3083+
parser = argparse.ArgumentParser()
3084+
xparser = parser.add_subparsers().add_parser('X')
3085+
xparser.set_defaults(foo=1)
3086+
self.assertEqual(NS(foo=2), parser.parse_args(['X'], NS(foo=2)))
3087+
30823088
def test_set_defaults_same_as_add_argument(self):
30833089
parser = ErrorRaisingArgumentParser()
30843090
parser.set_defaults(w='W', x='X', y='Y', z='Z')
Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
1+
Fix an issue where argparse would not preserve values in a provided namespace
2+
when using a subparser with defaults.

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