kunit: add bash completion

Currently, kunit.py has many subcommands and options, making it difficult
to remember them without checking the help message.

Add --list-cmds and --list-opts to kunit.py to get available commands and
options, use those outputs in kunit-completion.sh to show completion.

This implementation is similar to perf and tools/perf/perf-completion.sh.

Example output:
  $ source tools/testing/kunit/kunit-completion.sh
  $ ./tools/testing/kunit/kunit.py [TAB][TAB]
  build   config  exec    parse   run
  $ ./tools/testing/kunit/kunit.py run --k[TAB][TAB]
  --kconfig_add  --kernel_args  --kunitconfig

Link: https://lore.kernel.org/r/20260117-kunit-completion-v2-1-cabd127d0801@gmail.com
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Ryota Sakamoto <sakamo.ryota@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Documentation/dev-tools/kunit/run_wrapper.rst

@@ -335,3 +335,12 @@ command line arguments:
 
 - ``--list_tests_attr``: If set, lists all tests that will be run and all of their
   attributes.
+
+Command-line completion
+==============================
+
+The kunit_tool comes with a bash completion script:
+
+.. code-block:: bash
+
+	source tools/testing/kunit/kunit-completion.sh

tools/testing/kunit/kunit-completion.sh

@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0
+# bash completion support for KUnit
+
+_kunit_dir=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+
+_kunit()
+{
+	local cur prev words cword
+	_init_completion || return
+
+	local script="${_kunit_dir}/kunit.py"
+
+	if [[ $cword -eq 1 && "$cur" != -* ]]; then
+		local cmds=$(${script} --list-cmds 2>/dev/null)
+		COMPREPLY=($(compgen -W "${cmds}" -- "$cur"))
+		return 0
+	fi
+
+	if [[ "$cur" == -* ]]; then
+		if [[ -n "${words[1]}" && "${words[1]}" != -* ]]; then
+			local opts=$(${script} ${words[1]} --list-opts 2>/dev/null)
+			COMPREPLY=($(compgen -W "${opts}" -- "$cur"))
+			return 0
+		else
+			local opts=$(${script} --list-opts 2>/dev/null)
+			COMPREPLY=($(compgen -W "${opts}" -- "$cur"))
+			return 0
+		fi
+	fi
+}
+
+complete -o default -F _kunit kunit.py
+complete -o default -F _kunit kunit
+complete -o default -F _kunit ./tools/testing/kunit/kunit.py

tools/testing/kunit/kunit.py

@@ -328,6 +328,17 @@ def get_default_build_dir() -> str:
 		return os.path.join(os.environ['KBUILD_OUTPUT'], '.kunit')
 	return '.kunit'
 
+def add_completion_opts(parser: argparse.ArgumentParser) -> None:
+	parser.add_argument('--list-opts',
+			    help=argparse.SUPPRESS,
+			    action='store_true')
+
+def add_root_opts(parser: argparse.ArgumentParser) -> None:
+	parser.add_argument('--list-cmds',
+			    help=argparse.SUPPRESS,
+			    action='store_true')
+	add_completion_opts(parser)
+
 def add_common_opts(parser: argparse.ArgumentParser) -> None:
 	parser.add_argument('--build_dir',
 			    help='As in the make command, it specifies the build '
@@ -379,6 +390,8 @@ def add_common_opts(parser: argparse.ArgumentParser) -> None:
 			    help='Additional QEMU arguments, e.g. "-smp 8"',
 			    action='append', metavar='')
 
+	add_completion_opts(parser)
+
 def add_build_opts(parser: argparse.ArgumentParser) -> None:
 	parser.add_argument('--jobs',
 			    help='As in the make command, "Specifies  the number of '
@@ -574,6 +587,7 @@ subcommand_handlers_map = {
 def main(argv: Sequence[str]) -> None:
 	parser = argparse.ArgumentParser(
 			description='Helps writing and running KUnit tests.')
+	add_root_opts(parser)
 	subparser = parser.add_subparsers(dest='subcommand')
 
 	# The 'run' command will config, build, exec, and parse in one go.
@@ -608,12 +622,28 @@ def main(argv: Sequence[str]) -> None:
 	parse_parser.add_argument('file',
 				  help='Specifies the file to read results from.',
 				  type=str, nargs='?', metavar='input_file')
+	add_completion_opts(parse_parser)
 
 	cli_args = parser.parse_args(massage_argv(argv))
 
 	if get_kernel_root_path():
 		os.chdir(get_kernel_root_path())
 
+	if cli_args.list_cmds:
+		print(" ".join(subparser.choices.keys()))
+		return
+
+	if cli_args.list_opts:
+		target_parser = subparser.choices.get(cli_args.subcommand)
+		if not target_parser:
+			target_parser = parser
+
+		# Accessing private attribute _option_string_actions to get
+		# the list of options. This is not a public API, but argparse
+		# does not provide a way to inspect options programmatically.
+		print(' '.join(target_parser._option_string_actions.keys()))
+		return
+
 	subcomand_handler = subcommand_handlers_map.get(cli_args.subcommand, None)
 
 	if subcomand_handler is None:

tools/testing/kunit/kunit_tool_test.py

@@ -11,11 +11,13 @@ from unittest import mock
 
 import tempfile, shutil # Handling test_tmpdir
 
+import io
 import itertools
 import json
 import os
 import signal
 import subprocess
+import sys
 from typing import Iterable
 
 import kunit_config
@@ -886,5 +888,24 @@ class KUnitMainTest(unittest.TestCase):
 			mock.call(args=None, build_dir='.kunit', filter_glob='suite2.test1', filter='', filter_action=None, timeout=300),
 		])
 
+	@mock.patch.object(sys, 'stdout', new_callable=io.StringIO)
+	def test_list_cmds(self, mock_stdout):
+		kunit.main(['--list-cmds'])
+		output = mock_stdout.getvalue()
+		output_cmds = sorted(output.split())
+		expected_cmds = sorted(['build', 'config', 'exec', 'parse', 'run'])
+		self.assertEqual(output_cmds, expected_cmds)
+
+	@mock.patch.object(sys, 'stdout', new_callable=io.StringIO)
+	def test_run_list_opts(self, mock_stdout):
+		kunit.main(['run', '--list-opts'])
+		output = mock_stdout.getvalue()
+		output_cmds = set(output.split())
+		self.assertIn('--help', output_cmds)
+		self.assertIn('--kunitconfig', output_cmds)
+		self.assertIn('--jobs', output_cmds)
+		self.assertIn('--kernel_args', output_cmds)
+		self.assertIn('--raw_output', output_cmds)
+
 if __name__ == '__main__':
 	unittest.main()