Robotics StackExchange | Archived questions

ros2 launch error: Failed to load entry point

Hello, I have been playing around with turtlebot3 burger installed with ubuntu 20.04 and ros2 foxy. My remote PC installed with the same setup as the turtlebot.

on my turtlebot, I am able to run ros2 launch turtlebot3_bringup robot.launch.py or any launch files for that matter but cannot run launch files on the remote PC like below.

ros2 launch turtlebot3_cartographer cartographer.launch.py

I get this error when I do try to launch something on the PC: 

Failed to load entry point 'launch': [Errno 2] No such file or directory: '/home/hle/Desktop/compsci/ros/slam_capstone/install/launch/share/launch/frontend/grammar.lark'
Traceback (most recent call last):
  File "/opt/ros/foxy/bin/ros2", line 11, in <module>
    load_entry_point('ros2cli==0.9.11', 'console_scripts', 'ros2')()
  File "/opt/ros/foxy/lib/python3.8/site-packages/ros2cli/cli.py", line 39, in main
    add_subparsers_on_demand(
  File "/opt/ros/foxy/lib/python3.8/site-packages/ros2cli/command/__init__.py", line 237, in add_subparsers_on_demand
    extension = command_extensions[name]
KeyError: 'launch'

I get this same error when running command

ros2 launch -h

Please let me know if there are any information needed that I may have left out.

Asked by huybeme on 2022-02-28 21:40:31 UTC

Comments

I have sort of found a work around solution at the moment would like to solve the problem at its root so here is what I did.

I went to ~/opt/ros/foxy/share/launch/ and copied the frontend/ folder to the directory on my error above. I also copied some of the dependencies from the package.xml and added it to the other directory's package.xml

so far I am able to run ros2 launch command properly now.

However, is there a way to correct the path/entry point to the launch command?

Asked by huybeme on 2022-03-01 19:31:23 UTC

It would be nice to see how the launch file looks like, from this error message one can only deduce that something inside that launch file is pointing to a file that hasn't been copied to that directory during the building process (you can check you CMakeLists.txt for that).

Asked by Serafadam on 2022-03-10 19:35:51 UTC

Hi Serafadak, sorry for a very late response. Although I have found a work around when the error prompts, the issue still remains. Any launch file I run will run into this error. It seems like sometimes when I 'colcon build', something happens and the default directory for the launch grammar.lark file gets changed which is why I have to copy and paste the appropriate files to the directory stated in the error code. As for a launch file example, here is one that I always run that will prompt when this error pops up: https://github.com/ROBOTIS-GIT/turtlebot3/blob/foxy-devel/turtlebot3_bringup/launch/robot.launch.py

Is there a way do you know of that I can correct its directory for entry point back to the default /opt/ros/foxy directory?

Asked by huybeme on 2022-05-09 21:53:13 UTC

Answers