pytest discovery clobbers PYTHONPATH

[couteau]

Type: Bug

Behavior

Pytest test discovery fails, reporting a missing import. The relevant package exists and is on the PYTHONPATH in my conda environment, but the python extension resets the PYTHONPATH to /Users/username/.vscode/extensions/ms-python.python-2025.16.0-darwin-arm64/python_files when it runs test discovery (and perhaps also tests, but I can't get that far). Running from the command line works fine.

This is a new problem -- not sure exactly when it started but I was not having it in September, so maybe with the most recent version.

Steps to reproduce:

1. Create a conda environment
2. Install packages in some location other than site-packages (e.g., $CONDA_PREFIX/share/python)
3. Set the PYTHONPATH to the location of the package in the conda environement (e.g., using conda env config vars)
4. Create a project in vscode
5. Create a pytest test in the project that imports the package in the non-standard location
6. Click the refresh tests button

Diagnostic data

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

2025-10-20 12:54:38.840 [info] Running installed packages checker:  {
  id: '/Users/username/anaconda3/envs/my_conda_env/bin/python',
  displayName: 'my_conda_env (3.12.11)',
  detailedDisplayName: 'my_conda_env',
  envType: 'Conda',
  envPath: '/Users/username/anaconda3/envs/my_conda_env',
  type: 'Conda',
  path: '/Users/username/anaconda3/envs/my_conda_env/bin/python',
  version: {
    raw: '3.12.11',
    major: 3,
    minor: 12,
    patch: 11,
    build: [],
    prerelease: []
  },
  sysVersion: '3.12.11',
  architecture: 3,
  sysPrefix: '/Users/username/anaconda3/envs/my_conda_env'
} /Users/username/.vscode/extensions/ms-python.python-2025.16.0-darwin-arm64/python_files/installed_check.py /Users/username/Source/my_project/pyproject.toml
2025-10-20 12:54:38.840 [info] > ~/anaconda3/envs/my_conda_env/bin/python ~/.vscode/extensions/ms-python.python-2025.16.0-darwin-arm64/python_files/installed_check.py ./pyproject.toml
2025-10-20 12:56:03.065 [info] Discover tests for workspace name: my_project - uri: /Users/username/Source/my_project
2025-10-20 12:56:03.073 [info] arg: --rootdir already exists in args, not adding.
2025-10-20 12:56:03.073 [info] Environment variables set for pytest discovery: PYTHONPATH=/Users/username/.vscode/extensions/ms-python.python-2025.16.0-darwin-arm64/python_files, TEST_RUN_PIPE=/var/folders/7b/j6zzgg8j1v3d83xn_msb1xnw0000gn/T/python-test-discovery-59c4eedeb9119bd3c322
2025-10-20 12:56:03.253 [error] ImportError while loading conftest '/Users/username/Source/my_project/tests/conftest.py'.

2025-10-20 12:56:03.277 [error] tests/conftest.py:36: in <module>
    from qgis.core import (
E   ModuleNotFoundError: No module named 'qgis'

2025-10-20 12:56:03.297 [error] Subprocess exited unsuccessfully with exit code 4 and signal null on workspace /Users/username/Source/project_name
2025-10-20 12:56:03.297 [error] pytest test discovery error for workspace:  /Users/username/Source/project_name 
  
 The python test process was terminated before it could exit on its own, the process errored with: Code: 4, Signal: null for workspace /Users/username/Source/project_name

Extension version: 2025.16.0
VS Code version: Code 1.105.1 (7d842fb85a0275a4a8e4d7e040d2625abbf7f084, 2025-10-14T22:33:36.618Z)
OS version: Darwin arm64 24.6.0
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 3.10.18
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Conda
• Value of the python.languageServer setting: Default

User Settings

condaPath: "/Users/username/anaconda3/bin/conda"

languageServer: "Pylance"

testing
• pytestArgs: ""
• pytestEnabled: true

experiments
• optInto: ["pythonTestAdapter"]

Installed Extensions

Extension Name	Extension Id	Version
cmake-tools	ms-	1.21.36
copilot	Git	1.372.0
copilot-chat	Git	0.32.3
cpptools	ms-	1.28.3
cpptools-extension-pack	ms-	1.3.1
cpptools-themes	ms-	2.0.0
datawrangler	ms-	1.22.0
debugpy	ms-	2025.14.1
even-better-toml	tam	0.21.2
hexeditor	ms-	1.11.1
intellicode-api-usage-examples	Vis	0.2.9
js-debug	ms-	1.105.0
js-debug-companion	ms-	1.1.3
js-debug-nightly	ms-	2025.10.117
jupyter	ms-	2025.9.1
jupyter-keymap	ms-	1.1.2
jupyter-renderers	ms-	1.3.0
makefile-tools	ms-	0.12.17
prettier-vscode	esb	11.0.0
python	ms-	2025.16.0
remote-containers	ms-	0.427.0
ruff	cha	2025.28.0
vscode-containers	ms-	2.2.0
vscode-js-profile-table	ms-	1.0.10
vscode-jupyter-cell-tags	ms-	0.1.9
vscode-jupyter-slideshow	ms-	0.1.6
vscode-pylance	ms-	2025.8.3
vscode-python-envs	ms-	1.10.0
vscode-typescript-next	ms-	6.0.20251019
vscodeintellicode	Vis	1.3.2

System Info

Item	Value
CPUs	Apple M1 Max (10 x 2400)
GPU Status	2d_canvas: enabled 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_graphite: enabled_on trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	4, 4, 4
Memory (System)	64.00GB (0.35GB free)
Process Argv	--crash-reporter-id 7daef490-db9b-4617-abaa-559a02220920
Screen Reader	no
VM	0%

A/B Experiments

vsliv368:30146709
pythonvspyt551:31249599
binariesv615:30325510
nes-control-qres:31402648
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31334701
aj953862:31281341
4f60g487:31327383
nes-set-on:31340697
6abeh943:31336334
envsactivate1:31353494
gendocstringt:31395207
gaj49834:31404438
cloudbuttont:31379625
todos-1:31390405
qwen_all_req:31402696
treatment_gpt5applypatchexclusively:31398171
3efgi100_wstrepl:31403338
46f5c265:31402810
trigger-command-fix:31379601
cmp-cht-code-treat-node-fetcher:31399471
auto_model_enabled:31385282
use-responses-api:31390855
applesignin:31399435
defaultusage:31403421
auto_g2946222:31402681
nes-subseq-delay-200:31400950
je187915:31401254

[eleanorjboyd]

Hi- to clarify when you say " python extension resets the PYTHONPATH to /Users/username/.vscode/extensions/ms-python.python-2025.16.0-darwin-arm64/python_files when it runs test discover" is that all that is left in the PYTHON PATH for you?

[github-actions]

Because we have not heard back with the information we requested, we are closing this issue for now. If you are able to provide the info later on, then we will be happy to re-open this issue to pick up where we left off.

Happy Coding!