Debug tests with Visual Studio Code¶

Debugging Launchpad in Visual Studio Code (VS Code) can streamline your development process by allowing you to inspect code, set breakpoints, and interactively solve problems. This guide will help you set up VS Code for debugging Launchpad tests and the appserver.

SSH access to LXD containers within VS Code¶

To run and debug Launchpad tests inside a local LXD container using Visual Studio Code, you need to set up SSH access. This guide assumes that SSH has been configured as described in the Running section.

Install the SSH Extension: Install the ‘Remote - SSH’ extension from the VS Code marketplace to enable SSH capabilities within your development environment.
Open Command Palette: Press Ctrl+Shift+P (or Cmd+Shift+P on macOS) and type ‘Remote-SSH: Connect to Host’, then select it.
Select Your LXD Container: Choose your previously configured LXD container from the list of available SSH hosts or add a new one.
Start Working: Once connected, VS Code will treat the container as a local environment. You can now navigate to your project directory and run or debug tests without any additional configuration changes.

Create the `launch.json` file¶

First, you need to set up your debugging environment by creating a launch.json file in the .vscode directory at the root of your project. This file will tell VS Code how to launch the debugger for your project’s tests. Here’s how the launch.json file should look:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Debug Launchpad Tests",
            "type": "debugpy",
            "request": "launch",
            "program": "${workspaceFolder}/bin/test",
            "console": "integratedTerminal",
            "args": [
                "-vvc", "-t", "${command:pickArgs}"
            ]
        }
    ]
}

You can find this configuration file inside the dev-configs repository, under vscode/ruinedyourlife/launch.json.

This configuration uses the Python debugger extension (debugpy) and specifies that the debugger should start the test script located in your project’s bin directory, with verbose output. The additional test selection arguments allow you to specify which test to debug; when you launch the debugger, a pop-up window will appear, prompting you to input the test name you want to debug using the ${command:pickArgs} command.

Debug the Launchpad appserver¶

To debug the Launchpad appserver, you first need to create a tasks.json file under the .vscode directory. This file will define a task to build the necessary Launchpad services before launching the server.

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Build Launchpad services",
            "type": "shell",
            "command": "make",
            "args": [
                "build",
                "inplace",
                "stop"
            ],
            "problemMatcher": [],
            "presentation": {
                "reveal": "always",
                "panel": "shared"
            }
        }
    ]
}

Next, add the following configuration to your launch.json file. This will allow you to launch and debug the Launchpad server.

{
    "name": "Debug Launchpad Server",
    "type": "debugpy",
    "request": "launch",
    "program": "${workspaceFolder}/bin/run",
    "args": [
        "-r",
        "librarian,bing-webservice,memcached,rabbitmq",
        "-i",
        "development"
    ],
    "console": "integratedTerminal",
    "preLaunchTask": "Build Launchpad services",
    "justMyCode": false
}

This configuration defines a launch profile named “Debug Launchpad Server” that runs the bin/run script with the necessary arguments to start the appserver in development mode. The preLaunchTask ensures that the “Build Launchpad services” task is executed before the debugger starts, and "justMyCode": false allows the debugger to step into library code as well.

Once you have added these configurations, you can launch the debugger.

Launch the debugger¶

After setting up the launch.json, you can start the debugger using one of the following methods:

Command Palette: - Open the Command Palette (Ctrl+Shift+P or Cmd+Shift+P on macOS) and type ‘python debugger’. Select Python Debugger: Debug using launch.json.
Debug Menu in Activity Bar: - Click on the Debug icon on the left/right Activity Bar (or press Ctrl+Shift+D), select the configuration you wish to launch (which are picked from your launch.json file), then click the green start icon at the top.
Debug Icon in Tab Bar: - At the top right, you’ll see a debug icon with a dropdown for your debug configurations—select the Python Debugger: Debug using launch.json option. Select the configuration you wish to launch.

Additional resources¶

For more detailed information on debugging with Visual Studio Code, especially for Python applications, refer to the VS Code Python debugging documentation.

To customize your debugging experience further, such as using conditional breakpoints, logpoints, and more, consult the VS Code general debugging documentation.