Debugger does not break when calling back from C created thread

[ido-ran]

I have first open this bug in microsoft/vscode-python#14098 - but maybe here it's more appropriate.

Environment data

• Version: 1.49.0 (system setup)
• Commit: e790b931385d72cf5669fcefc51cdf65990efa5d
• Date: 2020-09-10T13:22:08.892Z
• Electron: 9.2.1
• Chrome: 83.0.4103.122
• Node.js: 12.14.1
• V8: 8.3.110.13-electron.0
• OS: Windows_NT x64 10.0.19041
• Extension version (available under the Extensions sidebar): v2020.8.109390
• Python version (& distribution if applicable, e.g. Anaconda): 3.8.0
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): venv
• Relevant/affected Python packages and their versions: none
• Relevant/affected Python-related VS Code extensions and their versions: none
• Value of the python.languageServer setting: Jedi

Expected behaviour

The debugger will break on the breakpoint set in VS Code.

Actual behaviour

The debugger does not break on the breakpoint set.

Steps to reproduce:

1. Clone https://github.com/ido-ran/vscode-python-cthread-debugging
2. Run create-venv.sh once to create venv
3. Run build_thrd.sh to build Cyton extension
4. Open test_threading.py in VS Code
5. Add breakpoint on the print statement in handler function
6. Start debug by pressing F5 or open the Run tab and click Start Debugging

[fabioz]

This is a known issue...

We already tried some approaches and still haven't been able to come up with a good solution to do that in the general case, so, for now, you're required to manually ask for non-python started threads to be traced.

To do that you can use the following api:

import debugpy
debugpy.debug_this_thread()

[ido-ran]

Thanks @fabioz. I've added this call into my pyx file and that is solving the problem in VS Code.
I actually need to make it work in PyCharm as well, using this snippet seems to cover all bases as both PyCharm and VS Code are using pydev under the hood:

    try:
        import pydevd
        pydevd.settrace(suspend=False)
    except:
        # ignore if debugger is not available
        pass

[fabioz]

Yeap, using the pydevd api directly should also work for debugpy ;)

p.s.: I'm closing as this is a known issue which is being tracked elsewhere.