Test Discovery assumes wrong encoding for stdout

[TimoRJensen]

Environment data

Commit: c3f126316369cd610563c75b1b1725e0679adfb3
Date: 2021-07-14T22:10:15.214Z (1 day ago)
Electron: 12.0.13
Chrome: 89.0.4389.128
Node.js: 14.16.0
V8: 8.9.255.25-electron.0
OS: Windows_NT x64 10.0.19043

[OK] [Copy]

• VS Code version: Version: 1.58.2 (user setup)
• Extension version (available under the Extensions sidebar): v2021.6.944021595
• OS and version: Windows 10 21H1
• Python version (& distribution if applicable, e.g. Anaconda): 3.8.5
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): venv
• Relevant/affected Python packages and their versions:
• Relevant/affected Python-related VS Code extensions and their versions:
• Value of the python.languageServer setting: "Pylance"

Expected behaviour

Test Discovery shows all the tests PYTEST discovers when run in Powershell via pytest.

Actual behaviour

Test Discovery fails with following stack trace:

Test Discovery failed: 
Error: Traceback (most recent call last):
  File "c:\Users\ich\.vscode\extensions\ms-python.python-2021.6.944021595\pythonFiles\testing_tools\run_adapter.py", line 22, in <module>
    main(tool, cmd, subargs, toolargs)
  File "c:\Users\ich\.vscode\extensions\ms-python.python-2021.6.944021595\pythonFiles\testing_tools\adapter\__main__.py", line 100, in main
    parents, result = run(toolargs, **subargs)
  File "c:\Users\ich\.vscode\extensions\ms-python.python-2021.6.944021595\pythonFiles\testing_tools\adapter\pytest\_discovery.py", line 30, in discover
    ec = _pytest_main(pytestargs, [_plugin])
  File "C:\Program Files (x86)\Python38-32\lib\contextlib.py", line 120, in __exit__
    next(self.gen)
  File "c:\Users\ich\.vscode\extensions\ms-python.python-2021.6.944021595\pythonFiles\testing_tools\adapter\util.py", line 251, in hide_stdio
    yield sio
  File "C:\Program Files (x86)\Python38-32\lib\contextlib.py", line 120, in __exit__
    next(self.gen)
  File "c:\Users\ich\.vscode\extensions\ms-python.python-2021.6.944021595\pythonFiles\testing_tools\adapter\util.py", line 239, in _temp_io
    buff = tmp.read()
  File "C:\Program Files (x86)\Python38-32\lib\tempfile.py", line 474, in func_wrapper
    return func(*args, **kwargs)
  File "C:\Program Files (x86)\Python38-32\lib\encodings\cp1252.py", line 23, in decode
    return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 61: character maps to <undefined>

Steps to reproduce:

1. I am not able to reproduce this as it works fine on my other 2 Windows machines. (One Windows 10 (slightly older build) and one being Win Server 2016

Misc

I asked about this on MS' Discord Server and received the following answer from @brettcannon:

It's a bug. Can you please open an issue at https://github.com/microsoft/vscode-python (specifically that code is making assumptions on the encoding of data sent to stdout that it probably shouldn't be making, which is then failing when we try to read the data back from the underlying file)?

[brettcannon]

I think the bug here is there's no checking what sys.stdout was using as an encoding before creating the temp file, and so there's a possible disconnect. I think the fix here is probably reading the encoding from the original sys.stdout and then specifying that for the temp file's encoding.

[botsman]

I am facing the same issue.
Though my case is a little bit complicated, the error and behavior seems to be the same:

I use pytest and in my project I have parametrized test class for a number of instances.
In order to initialize tests dynamically I use parametrized fixture, which initializes test only for instances, which have appropriate config json file.

The error happens for me in this initialization stage where my fixture tries to parse json files and fails with an error UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 187: ordinal not in range(128)

The problem is that one of my json configs have letter é.

Interestingly, this error does not occur if I run tests from the console, only when I run tests via VSCode.

I could provide a sample project if it is necessary.

[brettcannon]

We are about to embark on rewriting our test adapter code, so hopefully that will resolve this issue.

/cc @kimadeline

[kimadeline]

#17242

[TimoRJensen]

For everyone facing the same problem. It took me ages to realize the workaround for this was rather simple.
I "just" had to change the Windows Display Language from German to English (USA).

[eleanorjboyd]

Hello! We have just finished our testing rewrite and are beginning the roll out to users. If you are able, it would be very helpful to know if your issue still exists on the rewrite! To try it yourself, you need to be on the most recent release of the Python extension and add this setting to your users settings.json "python.experiments.optInto": ["pythonTestAdapter"].

You can confirm you have the rewrite enabled by setting "python.analysis.logLevel": "Trace", in your user settings then check for Experiment 'pythonTestAdapter' is active in your python logs.

Let me know if the rewrite fixes your issue. Thanks!

[eleanorjboyd]

closing as this should be fixed by changes made during #18346. Thanks