Add topic_name option to info verb

ros2bag/ros2bag/verb/info.py

@@ -22,7 +22,15 @@ class InfoVerb(VerbExtension):
 
     def add_arguments(self, parser, cli_name):  # noqa: D102
         add_standard_reader_args(parser)
+        parser.add_argument(
+            '-t', '--topic-name', action='store_true',
+            help='Only display topic names.'
+        )
 
     def main(self, *, args):  # noqa: D102
         m = Info().read_metadata(args.bag_path, args.storage)
-        print(m)
+        if args.topic_name:
+            for topic_info in m.topics_with_message_count:
+                print(topic_info.topic_metadata.name)
+        else:
+            print(m)

ros2bag/test/test_info.py

@@ -0,0 +1,69 @@
+# Copyright 2022 Open Source Robotics Foundation, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import contextlib
+from pathlib import Path
+import unittest
+
+from launch import LaunchDescription
+from launch.actions import ExecuteProcess
+import launch_testing
+import launch_testing.actions
+from launch_testing.tools.text import normalize_lineseps
+
+import pytest
+
+
+RESOURCES_PATH = Path(__file__).parent / 'resources'
+EXPECTED_OUTPUT = """/parameter_events
+/rosout
+"""
+
+
+@pytest.mark.rostest
+@launch_testing.markers.keep_alive
+def generate_test_description():
+    return LaunchDescription([launch_testing.actions.ReadyToTest()])
+
+
+class TestRos2BagInfo(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls, launch_service, proc_info, proc_output):
+        @contextlib.contextmanager
+        def launch_bag_command(self, arguments, **kwargs):
+            pkg_command_action = ExecuteProcess(
+                cmd=['ros2', 'bag', *arguments],
+                additional_env={
+                    'PYTHONUNBUFFERED': '1',
+                    'TZ': 'UTC',
+                },
+                name='ros2bag-cli',
+                output='screen',
+                **kwargs
+            )
+            with launch_testing.tools.launch_process(
+                    launch_service, pkg_command_action, proc_info, proc_output
+            ) as pkg_command:
+                yield pkg_command
+        cls.launch_bag_command = launch_bag_command
+
+    def test_info_with_topic_name_option(self):
+        """Test the output with --topic-name options."""
+        bag_path = RESOURCES_PATH / 'empty_bag'
+        arguments = ['info', '--topic-name', bag_path.as_posix()]
+        with self.launch_bag_command(arguments=arguments) as bag_command:
+            bag_command.wait_for_shutdown(timeout=5)
+        assert normalize_lineseps(bag_command.output) == EXPECTED_OUTPUT, \
+            'ros2bag CLI did not produce the expected output'