gh-135227: argparse: Use help as default description in add_parser

Lib/argparse.py

@@ -1259,17 +1259,18 @@ def add_parser(self, name, *, deprecated=False, **kwargs):
             if alias in self._name_parser_map:
                 raise ValueError(f'conflicting subparser alias: {alias}')
 
-        # create a pseudo-action to hold the choice help
-        if 'help' in kwargs:
-            help = kwargs.pop('help')
-            choice_action = self._ChoicesPseudoAction(name, aliases, help)
-            self._choices_actions.append(choice_action)
-        else:
-            choice_action = None
+        help_provided = 'help' in kwargs
+        help_text = kwargs.pop('help', None) if help_provided else None
 
-        # create the parser and add it to the map
+        # Set description default ONLY if:
+        if 'description' not in kwargs and help_text is not None:
+            kwargs['description'] = help_text
+
+        # Create the parser and pseudo-action
         parser = self._parser_class(**kwargs)
-        if choice_action is not None:
+        if help_provided:
+            choice_action = self._ChoicesPseudoAction(name, aliases, help_text)
+            self._choices_actions.append(choice_action)
             parser._check_help(choice_action)
         self._name_parser_map[name] = parser
 

Lib/test/test_argparse.py

@@ -2934,6 +2934,19 @@ def test_alias_help(self):
                 3                   3 help
             """))
 
+    def test_help_sets_default_description(self):
+        parser = argparse.ArgumentParser()
+        subparsers = parser.add_subparsers(dest="command")
+
+        sp1 = subparsers.add_parser("a", help="help a")
+        self.assertEqual(sp1.description, "help a")
+
+        sp2 = subparsers.add_parser("b", help="help b", description="explicit desc")
+        self.assertEqual(sp2.description, "explicit desc")
+
+        sp3 = subparsers.add_parser("c")
+        self.assertIsNone(sp3.description)
+
 # ============
 # Groups tests
 # ============

Misc/NEWS.d/next/Library/2025-06-07-15-10-22.gh-issue-135227.LPeDGt.rst

@@ -0,0 +1,3 @@
+The :meth:`!add_parser` method of the special action object returned by
+:meth:`argparse.ArgumentParser.add_subparsers` now uses the *help* value as
+the default *description* if none is provided. Patch by Swayam.