Pyton test discovery has suddenly stopped working

[erry-whiskypartners]

Type: Bug

Behaviour

It seems to start but then hang. No tests are ever discovered and the process is shown as running

2025-01-03 09:45:15.675 [info] > . ~/Library/Caches/pypoetry/virtualenvs/wp-inventory-O6dCq0oP-py3.11/bin/activate && echo 'e8b39361-0157-4923-80e1-22d70d46dee6' && python ~/.vscode/extensions/ms-python.python-2024.22.1-darwin-arm64/python_files/printEnvVariables.py
2025-01-03 09:45:15.675 [info] shell: bash
2025-01-03 09:45:15.710 [info] > ~/Library/Caches/pypoetry/virtualenvs/wp-inventory-O6dCq0oP-py3.11/bin/python -m pytest -p vscode_pytest --collect-only src --rootdir=.
2025-01-03 09:45:15.710 [info] cwd: .
2025-01-03 09:45:17.407 [info] ============================= test session starts ==============================
platform darwin -- Python 3.11.5, pytest-7.4.4, pluggy-1.5.0

2025-01-03 09:45:17.410 [info] django: version: 4.2.16, settings: core.settings (from ini)
rootdir: /Users/erry/repos/wp-inventory
configfile: pyproject.toml
plugins: ddtrace-2.14.4, Faker-30.8.0, cov-4.1.0, django-4.9.0, mock-3.14.0, xdist-3.6.1

2025-01-03 09:45:18.407 [info] collected 800 items

<Package serializers>
  <Module test_public_account_read_serializer.py>
    <Class TestPublicAccountBalanceSerializer>
      <Function test_valid_instance>
      <Function test_read_only_fields>
(truncated to fit github content, let me know if you want the full one)

It works if i do it manualy

python -m pytest --collect-only src            
============================= test session starts ==============================
platform darwin -- Python 3.11.5, pytest-7.4.4, pluggy-1.5.0
django: version: 4.2.16, settings: core.settings (from ini)
rootdir: /Users/erry/repos/wp-inventory
configfile: pyproject.toml
plugins: ddtrace-2.14.4, Faker-30.8.0, cov-4.1.0, django-4.9.0, mock-3.14.0, xdist-3.6.1
collected 800 items

<SNIP>
=============================== warnings summary ===============================
../../Library/Caches/pypoetry/virtualenvs/wp-inventory-O6dCq0oP-py3.11/lib/python3.11/site-packages/rest_framework/fields.py:992
  /Users/erry/Library/Caches/pypoetry/virtualenvs/wp-inventory-O6dCq0oP-py3.11/lib/python3.11/site-packages/rest_framework/fields.py:992: UserWarning: min_value should be a Decimal instance.
    warnings.warn("min_value should be a Decimal instance.")

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
========================= 800 tests collected in 0.75s =========================

This worked flawlessly until yesterday.Nothing has changed on our test set up.

Steps to reproduce:

1 Just do test discovery

Extension version: 2024.22.1
VS Code version: Code 1.96.2 (Universal) (fabdb6a30b49f79a7aba0f2ad9df9b399473380f, 2024-12-19T10:22:47.216Z)
OS version: Darwin arm64 24.1.0
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 3.11.5
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Poetry
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Pylance"

testing
• cwd: "<placeholder>"
• pytestArgs: "<placeholder>"
• pytestEnabled: true
• pytestPath: "<placeholder>"

Installed Extensions

Extension Name	Extension Id	Version
2077 theme	Endormi.2077-theme	1.5.3
Black Formatter	ms-python.black-formatter	2024.4.0
CSV to Table	phplasma.csv-to-table	1.4.1
Cyberpunk	max-SS.Cyberpunk	1.2.14
Dev Containers	ms-vscode-remote.remote-containers	0.394.0
Docker	ms-azuretools.vscode-docker	1.29.3
Doppler	doppler.doppler-vscode	0.0.10
GitHub Actions	github.vscode-github-actions	0.27.0
GitHub Pull Requests	GitHub.vscode-pull-request-github	0.102.0
GitLens — Git supercharged	eamodio.gitlens	16.1.1
HashiCorp Terraform	hashicorp.terraform	2.34.2
isort	ms-python.isort	2023.10.1
JavaScript Debugger	ms-vscode.js-debug	1.96.0
JavaScript Debugger Companion Extension	ms-vscode.js-debug-companion	1.1.3
Lifeline: Clock & battery	kjhx.vscode-lifeline	1.2.0
Makefile Tools	ms-vscode.makefile-tools	0.11.13
Prettier - Code formatter	esbenp.prettier-vscode	11.0.0
Prettier SQL VSCode	inferrinizzard.prettier-sql-vscode	1.6.0
Pylance	ms-python.vscode-pylance	2024.12.1
Python	ms-python.python	2024.22.1
Python Debugger	ms-python.debugpy	2024.14.0
Rainbow CSV	mechatroner.rainbow-csv	3.13.0
Remote - SSH	ms-vscode-remote.remote-ssh	0.116.1
Remote - SSH: Editing Configuration Files	ms-vscode-remote.remote-ssh-edit	0.87.0
Remote Explorer	ms-vscode.remote-explorer	0.4.3
Spectral	stoplight.spectral	1.1.4
Table Visualizer for JavaScript Profiles	ms-vscode.vscode-js-profile-table	1.0.10
Trailing Spaces	shardulm94.trailing-spaces	0.4.1
Vim	vscodevim.vim	1.29.0
XML	redhat.vscode-xml	0.27.2
YAML	redhat.vscode-yaml	1.15.0

System Info

Item	Value
CPUs	Apple M1 Pro (8 x 2400)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on 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: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	4, 7, 11
Memory (System)	16.00GB (0.08GB free)
Process Argv	--crash-reporter-id 850d1a48-013f-4f6c-9e0c-7a68499eea23
Screen Reader	no
VM	0%

A/B Experiments

vsliv368cf:30146710
vspor879:30202332
vspor708:30202333
vspor363:30204092
vscod805:30301674
binariesv615:30325510
vsaa593:30376534
py29gd2263:31024239
c4g48928:30535728
azure-dev_surveyone:30548225
a9j8j154:30646983
962ge761:30959799
pythonnoceb:30805159
pythonmypyd1:30879173
2e7ec940:31000449
pythontbext0:30879054
cppperfnew:31000557
dsvsc020:30976470
pythonait:31006305
dsvsc021:30996838
dvdeprecation:31068756
dwnewjupytercf:31046870
newcmakeconfigv2:31071590
nativerepl2:31139839
pythonrstrctxt:31112756
nativeloc1:31192215
cf971741:31144450
iacca1:31171482
notype1:31157159
5fd0e150:31155592
dwcopilot:31170013
stablechunks:31184530
6074i472:31201624

[dvirbech]

Same as #24656

[ousmaneTra]

same here since a couple of days

[dougppaz]

same here, macos

I went back to version 22.0 and it started working again

[SiorMeir]

Same with MacOS. Tested on 2 different systems. Happens in pre-release version as well

[mucki-at]

I have been debugging this, and there seems to be a problem with the pipe communication in the send_message method in vscode_pytest/init.py:

vscode-python/python_files/vscode_pytest/__init__.py

Line 947 in de988ff

__writer.write(request)

It seems that if the length of the request exceeds a certain size the write() call never completes. Since there is no timeout mechanism in place the test discovery just hangs forever.