Arguments in launch.json not being used

[mhdadk]

Type: Bug

My current workspace directory is path/to/project. Here is what is in this directory:

.vscode/
| launch.json
figures/
scripts/
| test_chdir.py

Here is what is in 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": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "justMyCode": true,
            "cwd": "${fileDirname}"
        }
    ]
}

Because I set cwd to "${fileDirname}", then I am expecting that when I run the file scripts/test_chdir.py, the working directory will be scripts. However, that is not the case, and no matter what I do, the working directory is always the workspace directory, i.e. path/to/project. To demo this, the file scripts/test_chdir.py contains:

import os
print(os.getcwd())
assert os.path.isdir("../figures")

When I run this using the “Debug Python file” button, I get the error:

Exception has occurred: AssertionError
exception: no description

I don’t get this error if I cd into the scripts folder and then run python test_chdir.py. In fact, when I change the "program" entry in my launch.json file to be path/to/project/X.py:

{
    // 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": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "/path/to/project/X.py",
            "console": "integratedTerminal",
            "justMyCode": true,
            "cwd": "${fileDirname}"
        }
    ]
}

which is a file that doesn't exist, I still get the same assertion error above, which means that VS code does not even check the launch.json file. What am I missing here?

Extension version: 2022.20.1
VS Code version: Code 1.74.1 (1ad8d514439d5077d2b0b7ee64d2ce82a9308e5a, 2022-12-14T10:30:51.966Z)
OS version: Windows_NT x64 10.0.22621
Modes:
Sandboxed: No

System Info

Item	Value
CPUs	12th Gen Intel(R) Core(TM) i7-12700H (20 x 2688)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: disabled_off direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_renderer: enabled_on video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: disabled_off
Load (avg)	undefined
Memory (System)	15.72GB (8.23GB free)
Process Argv	--crash-reporter-id f3fde2b4-4f86-4e12-b740-e1ffa600c042
Screen Reader	no
VM	0%

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[mhdadk]

I found out what the problem is and its solution. It turns out that whether the "cwd" parameter in the launch.json file will be read or not will depend on how the Python file is run in VS code. From this answer, it seems that if the Python file is run using one of the following actions:

• Run > Run Without Debugging (or Ctrl+F5)
• Run > Start Debugging (or F5)

then the "cwd" parameter in the launch.json file will be read, and the correct working directory will be set.

However, if the Python file is run using either the "Run Python File" button or the "Debug Python File" button in the top-right of the editor window, then the "cwd" parameter in the launch.json file will not be read, and the working directory will not be the expected one. According to the answer linked to above, it is possible to force VS code to read the "cwd" parameter in the launch.json file when clicking on the "Debug Python File" button in the top-right of the editor window by setting the "purpose" parameter (more details here) in the launch.json file to "debug-in-terminal", as shown below:

{
    // 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": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "justMyCode": true,
            "cwd": "${fileDirname}",
            "purpose": ["debug-in-terminal"]
        }
    ]
}