gh-96310: Fix a traceback in argparse when all options in a mutually …

…exclusive group are suppressed (GH-96311) Reproducer depends on terminal size - the traceback occurs when there's an option long enough so the usage line doesn't fit the terminal width. Option order is also important for reproducibility. Excluding empty groups (with all options suppressed) from inserts fixes the problem. (cherry picked from commit 5f7df88) Co-authored-by: Daniel Mach <daniel.mach@suse.com>
serhiy-storchaka · Feb 21, 2024 · Feb 21, 2024 · Feb 21, 2024 · 0e71ea4e2dce779af4e2b24b7c3c9b87be99cb48
commit 0e71ea4e2dce779af4e2b24b7c3c9b87be99cb48
diff --git a/Lib/argparse.py b/Lib/argparse.py
@@ -414,6 +414,8 @@ def _format_actions_usage(self, actions, groups):
                             suppressed_actions_count += 1
 
                     exposed_actions_count = group_action_count - suppressed_actions_count
+                    if not exposed_actions_count:
+                        continue
 
                     if not group.required:
                         if start in inserts:

diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
@@ -2743,6 +2743,27 @@ def test_help(self):
               '''
         self.assertEqual(parser.format_help(), textwrap.dedent(expected))
 
+    def test_help_subparser_all_mutually_exclusive_group_members_suppressed(self):
+        self.maxDiff = None
+        parser = ErrorRaisingArgumentParser(prog='PROG')
+        commands = parser.add_subparsers(title="commands", dest="command")
+        cmd_foo = commands.add_parser("foo")
+        group = cmd_foo.add_mutually_exclusive_group()
+        group.add_argument('--verbose', action='store_true', help=argparse.SUPPRESS)
+        group.add_argument('--quiet', action='store_true', help=argparse.SUPPRESS)
+        longopt = '--' + 'long'*32
+        longmeta = 'LONG'*32
+        cmd_foo.add_argument(longopt)
+        expected = f'''\
+            usage: PROG foo [-h]
+                            [{longopt} {longmeta}]
+
+            options:
+              -h, --help            show this help message and exit
+              {longopt} {longmeta}
+              '''
+        self.assertEqual(cmd_foo.format_help(), textwrap.dedent(expected))
+
     def test_empty_group(self):
         # See issue 26952
         parser = argparse.ArgumentParser()

diff --git a/Misc/NEWS.d/next/Library/2022-08-26-15-50-53.gh-issue-96310.0NssDh.rst b/Misc/NEWS.d/next/Library/2022-08-26-15-50-53.gh-issue-96310.0NssDh.rst
@@ -0,0 +1,2 @@
+Fix a traceback in :mod:`argparse` when all options in a mutually exclusive
+group are suppressed.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix a traceback in :mod:`argparse` when all options in a mutually exclusive
		group are suppressed.