SyntaxError: Unexpected token in JSON at position 23851

[brgirgis]

Environment data

• VS Code version: 1.39.2
• Extension version (available under the Extensions sidebar): 2019.10.44104
• OS and version: MS Windows 10
• Python version (& distribution if applicable, e.g. Anaconda): 3.7.4
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): miniconda
• Relevant/affected Python packages and their versions: pytest
• Jedi or Language Server? (i.e. what is "python.jediEnabled" set to; more info How to update the language server to the latest stable version #3977): N/A

Expected behaviour

Discover all unit tests correctly with no problems as long as pythonFiles/testing_tools/run_adapter.py returns the correct JSON data

Actual behaviour

While discovering, the loading machinery instantiates some dynamic libraries (DLLs) that output to the standard output. Apparently, run_adapter.py tries to capture all the output as the JSON object rather than the relevant return from pytest.

Steps to reproduce:

1. Create a C/C++ DLL that writes to stdout on load
2. Create a Python SWIG wrapper for that DLL
3. Write a pytest unittest that uses the SWIG wrapper
4. Test discovery fails

Logs

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

python c:\<private path>\ms-python.python-2019.10.44104\pythonFiles\testing_tools\run_adapter.py discover pytest -- -s -n 4 <private project>
Test Discovery failed: 
SyntaxError: Unexpected token E in JSON at position 23851

[kimadeline]

Duplicate of #6594