pythonGH-87041: Fix incorrect indentation in argparse help (pythonGH-…

…124230)

In case of usage a long command along with max_help_position more than
the length of the command, the command's help was incorrectly started
on the new line.

Co-authored-by: Pavel Ditenbir <pavel.ditenbir@gmail.com>

Lib/argparse.py

@@ -261,13 +261,12 @@ def add_argument(self, action):
 
  # find all invocations
  get_invocation = self._format_action_invocation
- invocations = [get_invocation(action)]
+ invocation_lengths = [len(get_invocation(action)) + self._current_indent]
  for subaction in self._iter_indented_subactions(action):
- invocations.append(get_invocation(subaction))
+ invocation_lengths.append(len(get_invocation(subaction)) + self._current_indent)
 
  # update the maximum item length
- invocation_length = max(map(len, invocations))
- action_length = invocation_length + self._current_indent
+ action_length = max(invocation_lengths)
  self._action_max_length = max(self._action_max_length,
  action_length)
 

Lib/test/test_argparse.py

@@ -4960,6 +4960,46 @@ def custom_type(string):
  version = ''
 
 
+class TestHelpUsageLongSubparserCommand(TestCase):
+ """Test that subparser commands are formatted correctly in help"""
+ maxDiff = None
+
+ def test_parent_help(self):
+ def custom_formatter(prog):
+ return argparse.RawTextHelpFormatter(prog, max_help_position=50)
+
+ parent_parser = argparse.ArgumentParser(
+ prog='PROG',
+ formatter_class=custom_formatter
+ )
+
+ cmd_subparsers = parent_parser.add_subparsers(title="commands",
+ metavar='CMD',
+ help='command to use')
+ cmd_subparsers.add_parser("add",
+ help="add something")
+
+ cmd_subparsers.add_parser("remove",
+ help="remove something")
+
+ cmd_subparsers.add_parser("a-very-long-command",
+ help="command that does something")
+
+ parser_help = parent_parser.format_help()
+ self.assertEqual(parser_help, textwrap.dedent('''\
+ usage: PROG [-h] CMD ...
+
+ options:
+ -h, --help show this help message and exit
+
+ commands:
+ CMD command to use
+ add add something
+ remove remove something
+ a-very-long-command command that does something
+ '''))
+
+
 # =====================================
 # Optional/Positional constructor tests
 # =====================================

Misc/NEWS.d/next/Library/2024-09-19-03-46-59.gh-issue-87041.9Ox7Bv.rst

@@ -0,0 +1 @@
+Fix a bug in :mod:`argparse` where lengthy subparser argument help is incorrectly indented.