Test discovery fails

[lseongjoo]

Environment data

• VS Code version: 1.42.1
• Extension version (available under the Extensions sidebar): 2020.2.64397
• OS and version: MacOS 10.15.3
• Python version (& distribution if applicable, e.g. Anaconda): Python 3.7.4 (Conda 4.8.1)
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): Docker Desktop for Mac 2.2.0
• Relevant/affected Python packages and their versions: pytest 5.3.5
• Relevant/affected Python-related VS Code extensions and their versions: Remote - Containers 0.101.1 Remote - SSH 0.49.0

Expected behaviour

Discovers pytest tests.

Actual behaviour

Test discovery fails. Pytest succeeds in CLI.

Steps to reproduce:

1. Suspects the problem occurs when some dependency module's API __del__ returns None

Logs

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

Traceback (most recent call last):
  File "/root/.vscode-server/extensions/ms-python.python-2020.2.64397/pythonFiles/testing_tools/run_adapter.py", line 15, in <module>
    main(tool, cmd, subargs, toolargs)
  File "/root/.vscode-server/extensions/ms-python.python-2020.2.64397/pythonFiles/testing_tools/adapter/__main__.py", line 87, in main
    parents, result = run(toolargs, **subargs)
  File "/root/.vscode-server/extensions/ms-python.python-2020.2.64397/pythonFiles/testing_tools/adapter/pytest/_discovery.py", line 39, in discover
    raise Exception("pytest discovery failed (exit code {})".format(ec))
Exception: pytest discovery failed (exit code 2)
Exception ignored in: <function DepedencyApi.__del__ at 0x7fe187dea9e0>
Traceback (most recent call last):
  File "/opt/conda/lib/python3.7/site-packages/dependency/module.py", line 179, in __del__
  File "/opt/conda/lib/python3.7/site-packages/dependency/module.py", line 210, in close
TypeError: 'NoneType' object is not callable

Output from Console under the Developer Tools panel (toggle Developer Tools on under Help; turn on source maps to make any tracebacks be useful by running Enable source map support for extension debugging)

Traceback (most recent call last):
  File "/root/.vscode-server/extensions/ms-python.python-2020.2.64397/pythonFiles/testing_tools/run_adapter.py", line 15, in <module>
    main(tool, cmd, subargs, toolargs)
  File "/root/.vscode-server/extensions/ms-python.python-2020.2.64397/pythonFiles/testing_tools/adapter/__main__.py", line 87, in main
    parents, result = run(toolargs, **subargs)
  File "/root/.vscode-server/extensions/ms-python.python-2020.2.64397/pythonFiles/testing_tools/adapter/pytest/_discovery.py", line 39, in discover
    raise Exception("pytest discovery failed (exit code {})".format(ec))
Exception: pytest discovery failed (exit code 2)
Exception ignored in: <function DepedencyApi.__del__ at 0x7fe187dea9e0>
Traceback (most recent call last):
  File "/opt/conda/lib/python3.7/site-packages/dependency/module.py", line 179, in __del__
  File "/opt/conda/lib/python3.7/site-packages/dependency/module.py", line 210, in close
TypeError: 'NoneType' object is not callable

at ChildProcess.<anonymous> (/root/.vscode-server/extensions/ms-python.python-2020.2.64397/out/client/extension.js:1:455844)
    at Object.onceWrapper (events.js:288:20)
    at ChildProcess.emit (events.js:200:13)
    at maybeClose (internal/child_process.js:1021:16)
    at Socket.<anonymous> (internal/child_process.js:430:11)
    at Socket.emit (events.js:200:13)
    at Pipe.<anonymous> (net.js:586:12)]

[ericsnowcurrently]

@lseongjoo, thanks for letting us know about this. We'll get back to you as soon as we can.

[ericsnowcurrently]

@lseongjoo, anything written to stderr while discovery is running will cause it to fail. (Unlike pytest itself, the extension does not ignore failures.)

We have plans for making extraneous output a non-issue. See #6594. Until then, there isn't much we can do about this problem.