[bug] Error: Failed to start debug session in Ubuntu 18.04

[ravijo]

Version Info

• Windows: (Version)
• Linux: Ubuntu OS 18.04.6 LTS
• ROS 1: Melodic
• ROS 2: Dist

<Version of the plugin>
Visual Studio Code v1.74.3
VSCode-ROS Extension v0.8.4

<Copy the Version information from the Help | About menu>

Version: 1.74.3
Commit: 97dec172d3256f8ca4bfb2143f3f76b503ca0534
Date: 2023-01-09T16:57:40.428Z
Electron: 19.1.8
Chromium: 102.0.5005.167
Node.js: 16.14.2
V8: 10.2.154.15-electron.0
OS: Linux x64 5.4.0-137-generic
Sandboxed: No

Bug Info

Can not attach or launch the debugger at all.

Repro steps

1. Clone rospy_tutorials
2. Use the following launch.json file:

   {
       // Use IntelliSense to learn about possible attributes.
       // Hover to view descriptions of existing attributes.
       // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
       "version": "0.2.0",
       "configurations": [
           {
               "name": "ROS: Launch",
               "type": "ros",
               "request": "launch",
               "target": "/home/ravi/test_ws/src/hello_tutorials/talker_listener.launch"
           },
   
           {
               "name": "ROS: Attach",
               "type": "ros",
               "request": "attach"
           }
       ]
   }
   

Expected Behavior

Debugger should run.

Additional Info

Please see two screen recordings below:

1. Recording: Attaching a running node

1.mp4

2. Recording: Launching nodes

2.mp4

I noticed that attaching a node is requesting authentication. But after providing the correct password, nothing happens. Similarly, the launching nodes show processes for a second but die/disappear immediately.

The developer tools are showing following following error:

[Extension Host] rejected promise not handled within 1 second: Error: Failed to start debug session!
[Extension Host] stack trace: Error: Failed to start debug session!
    at LaunchResolver.<anonymous> (/home/ravi/.vscode/extensions/ms-iot.vscode-ros-0.8.4/out/src/debugger/configuration/resolvers/ros1/launch.js:310:32)
    at Generator.next (<anonymous>)
    at fulfilled (/home/ravi/.vscode/extensions/ms-iot.vscode-ros-0.8.4/out/src/debugger/configuration/resolvers/ros1/launch.js:7:58)
    at process.processTicksAndRejections (node:internal/process/task_queues:96:5)

Please see a screenshot below:

The issues is also reported in SO

[ravijo]

It seems that error is caused due to Python 2.7 as indicated by the following screenshot:

Below is the launch.json file:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "ROS: Launch",
            "request": "launch",
            "target": "/home/ravi/test_ws/src/hello_tutorials/talker_listener.launch",
            "launch": [
                "rviz",
                "gz",
                "gzclient",
                "gzserver"
            ],
            "type": "ros"
        }
    ]
}

How to launch debugger in ROS Melodic?

[DerProfessor]

Hi,
I encountered the problem already with Python 3.6 under Ubuntu 18.04 (see #813).
In short the problem is that the VSCode Python Extension uses debugpy which dropped support for Python 2.7 and < Python 3.7. I work around the problem by reinstalling version 2022.2.1924087327
of the Python Extension which is the last to support Python 2.7 and 3.6. There are plans to support older Python versions again.

[ravijo]

@DerProfessor

It works like a charm! Thank you very much.

I hope the plans to support older versions get a green signal. Until then, I will keep using 2022.2.1924087327, as you suggested.

Thanks again.

[ravijo]

@DerProfessor

On another computer, having same OS and configuration, the "Launch" works but "Attach" doesn't while debugging python node.

May I request you to please have a look at #872

BTW, is there any log file in vscode? It would help to dig deeper in these issues. Thanks

[ooeygui]

There is a new log file support in 0.9.0. Using the "output" tab, select "ROS", which now shows logging. (Before it was only showing when debugged).

That said, these issues are related to the Python extension, not the ROS extension. Because of this dependency, Melodic is not supported by current versions of the ROS extension.

[ravijo]

@ooeygui

There is a new log file support in 0.9.0. Using the "output" tab, select "ROS", which now shows logging. (Before it was only showing when debugged).

Thank you very much for this helpful information.

That said, these issues are related to the Python extension, not the ROS extension. Because of this dependency, Melodic is not supported by current versions of the ROS extension

I understand. If you don't mind, may I ask you for a workaround please?