Allow -P to work for debugpy

[prumand]

Type: Bug

Behaviour

Expected vs. Actual

Adding the pythonArgs -P or -I to my launch config and call a script in module:

import sys
print(sys.path)

Expected:
Folder of file not in sys.path

Actual:
Folder of file is in sys.path

Steps to reproduce:

https://github.com/prumand/vscdoe-pythonargs-not-used

Diagnostic data

• Python version (& distribution if applicable, e.g. Anaconda): 3.11.4 and 3.9.6
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Poetry and plain macos
• Value of the python.languageServer setting: Default

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

['${workdspaceFodler}/test', '....']

User Settings

languageServer: "Pylance"

Extension version: 2023.14.0
VS Code version: Code 1.81.1 (Universal) (6c3e3dba23e8fadc360aed75ce363ba185c49794, 2023-08-09T22:20:33.924Z)
OS version: Darwin arm64 22.6.0
Modes:

System Info

Item	Value
CPUs	Apple M1 (8 x 24)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: disabled_off direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled
Load (avg)	1, 1, 2
Memory (System)	16.00GB (0.05GB free)
Process Argv	--crash-reporter-id 04e8682b-ee5a-4a44-a9ad-554467338aba
Screen Reader	no
VM	0%

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[Rich Chiodo (rchiodo)]

Karthik Nadig (@karthiknadig) isn't this handled by the extension? Those args are passed to python before running debugpy?

[Rich Chiodo (rchiodo)]

No never mind, they're passed by the launcher.

[Karthik Nadig (karthiknadig)]

No never mind, they're passed by the launcher.

That is correct.

[Rich Chiodo (rchiodo)]

Debugpy is passing that argument to debugpy, but it's not running your code. It's running the debugger:

Which likely is not your intent. You want -P to skip the script's folder on the sys.path. In this case it's skipping the folder where the debugpy adapter is located.

I think this would require a custom way to modify the sys.path before starting the app. Or you could modify your use case to use attach and launch your app with -P.

[Rich Chiodo (rchiodo)]

Meaning -P is working as expected:

Help from python.org for -P.

-P
Don’t prepend a potentially unsafe path to [sys.path](https://docs.python.org/3/library/sys.html#sys.path):

python -m module command line: Don’t prepend the current working directory.

python script.py command line: Don’t prepend the script’s directory. If it’s a symbolic link, resolve symbolic links.

python -c code and python (REPL) command lines: Don’t prepend an empty string, which means the current working directory.

[Rich Chiodo (rchiodo)]

Transferring to a discussion for up votes.