Support gevent 20.12.1

[plenzjr]

Environment data

• VS Code version: 1.52.1
• OS and version: Ubuntu 20.04
• Python version: 3.8.5
• Type of virtual environment used: venv
• Relevant/affected Python packages and their versions: Flask, gevent
• Relevant/affected Python-related VS Code extensions and their versions: Python, v2020.12.424452561,
• Debugpy version: 1.2.1

Actual behavior

Running the app from the debug console doesn't stop in some breakpoints and a warning is printed.

Expected behavior

Stop in all breakpoints and resolve warnings

Steps to reproduce:

• setup a virtualenv

  1. python3 -m ./.venv example
  2. source ./.venv/bin/activate

• install packages

  1. python3 -m pip install flask gevent

• create file run.py

from gevent import monkey
monkey.patch_all()


from flask import Flask
from datetime import datetime
import re


app = Flask(__name__)


@app.route("/")
def home():
    print('start')
    print('set a breakpoint')
    print('should stop')
    return "Hello, Flask!"


@app.route("/hello/<name>")
def hello_there(name):
    now = datetime.now()
    formatted_now = now.strftime("%A, %d %B, %Y at %X")

    # Filter the name argument to letters only using regular expressions. URL arguments
    # can contain arbitrary text, so we restrict to safe characters only.
    match_object = re.match("[a-zA-Z]+", name)

    if match_object:
        clean_name = match_object.group(0)
    else:
        clean_name = "Friend"

    content = "Hello there, " + clean_name + "! It's " + formatted_now
    return content


if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5100, debug=True, threaded=True, use_reloader=False)

• configure files:
  1. launch.json

{
    "configurations": [
        {
            "name": "Python: Flask",
            "type": "python",
            "request": "launch",
            "stopOnEntry": false,
            "module": "flask",
            "cwd": "${workspaceRoot}",
            "env": {
                "FLASK_APP": "run.py",
                "FLASK_ENV": "development",
                "FLASK_DEBUG": "0"
            },
            "args": [
                "run",
                "--no-debugger",
                "--no-reload",
                "--port=5100"
            ],
            "jinja": true,
            "console": "integratedTerminal",
            "justMyCode": false
        }
    ]
}

2. settings.json

{
    "python.pythonPath": "${env:HOME}/.venv/example/bin/python",
}

Run from debug

Logs

• logs from console

PYDEV DEBUGGER WARNING:
sys.settrace() should not be used when the debugger is being used.
This may cause the debugger to stop working correctly.
If this is needed, please check: 
http://pydev.blogspot.com/2007/06/why-cant-pydev-debugger-work-with.html
to see how to restore the debug tracing back correctly.
Call Location:
  File "${HOME}/.venv/example/lib/python3.8/site-packages/gevent/threadpool.py", line 157, in _before_run_task
    _sys.settrace(_get_thread_trace())


PYDEV DEBUGGER WARNING:
sys.settrace() should not be used when the debugger is being used.
This may cause the debugger to stop working correctly.
If this is needed, please check: 
http://pydev.blogspot.com/2007/06/why-cant-pydev-debugger-work-with.html
to see how to restore the debug tracing back correctly.
Call Location:
  File "${HOME}/.venv/example/lib/python3.8/site-packages/gevent/threadpool.py", line 162, in _after_run_task
    _sys.settrace(None)

[int19h]

If you're using gevent, you need to tell the debugger so that it tries to play nice with it:

"gevent": true

[fabioz]

Closing since it's expected that things don't work if "gevent": true is not specified in the launch configuration when using gevent.

Feel free to reopen if you find any issues when running with the gevent flag set.

[plenzjr]

Its set up on my env var, I just forget to add in this example

[fabioz]

Reopening then... can you provide the logs for the run?

i.e.:

• Open VS Code
• Select the command Extensions: Open Extensions Folder
• Locate the Python extension directory, typically of the form ms-python.python-2020..***
• In that directory ensure you do not have any debug*.log files, if you do, please delete them
• Go back into VS Code and modify your launch.json to add the setting "logToFile": true
• Start debugging
• When done, go back into the extension directory and upload the debug*.log files into this GitHub issue.

[fabioz]

I took a quick look at: https://github.com/gevent/gevent/blob/master/src/gevent/threadpool.py and it seems that gevent is now starting to call sys.settrace directly (this was added very recently in: gevent/gevent@5a05e82).

So, some work is probably needed on the debugger now that gevent is messing with the tracing that the debugger uses.

[plenzjr]

you are right,
gevent version 20.12.1 is causing the issue.
downgrade to the version 20.9.0 and run it without any problem.

thank you!

[fabioz]

I'll keep it open since we should support the newer release in the future...