Flask application process closes after a few seconds

[delucca]

Hi everyone.

I'm trying to setup the debugger in my Flask application (using Poetry) but when I launch the configuration for some reason the Flask application closes after a few seconds.

Everything is working (besides that). The application is launching properly, but after it finishes bootstrapping the process is closed after a few seconds.

About my env:

• I have one venv with debugpy and Poetry installed in it
• This is my dap config:

local setup_ok_dap, dap = pcall(require, "dap")
local setup_ok_dap_python, dap_python = pcall(require, "dap-python")

if not setup_ok_dap_python then
	return
end

dap_python.setup("~/.python-venvs/bin/python")

table.insert(dap.configurations.python, {
	name = "Launch Flask server",
	type = "python",
	request = "launch",
	console = "integratedTerminal",
	cwd = "${workspaceFolder}",
	program = "${env:PYTHON_VENV_PATH}/bin/poetry",
	args = {
		"run",
		"flask",
		"--no-debug",
		"run",
	},
})

Note

python-venvs is where my Python venv is located (both Debugpy and Poetry are installed there)

When I run the application, this is what I get in the intergrated terminal:

 * Serving Flask app 'prprocessor'
 * Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit

[Process exited 247]

(the Process exited message takes a few seconds to appear)

Also, I've already tried to remove the --no-debug flag, the result is the same. And, of course, if I run the poetry run flask run outside of the debugger it works as expected (the server is launched and stays live)

[mfussenegger]

Could be related to multiprocessing, see mfussenegger/nvim-dap#858 (comment)

You could set export DEBUGPY_LOG_DIR=/tmp/debugpy/ in the terminal where you start neovim/debugpy to get debugpy logs for more insights.

[delucca]

@mfussenegger thanks for your quick response!

So, I did as you suggested and got the following log files:
debugpy.adapter-16432.log
debugpy.launcher-16440.log
debugpy.pydevd.16445.log
debugpy.server-16445.log

I'm not sure what those logs mean 🤔

[mfussenegger]

I tried a more minimal version and it works for me:

Setup:

python -m venv venv
venv/bin/python -m pip install Flask

Create vscode/launch.json:

{
   "version": "0.2.0",
   "configurations": [
       {
           "type": "python",
           "request": "launch",
           "name": "Flask",
           "module": "flask",
           "args": ["--app", "foo", "run"],
           "console": "integratedTerminal"
       }
   ]
}

Create foo.py:

from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello():
    return "<p>Hello World</p>"

Maybe something odd going on with your use of poetry. I don't use it myself so I can't help you with that.
Maybe check the debugpy repository for more info on that.

[delucca]

@mfussenegger I was able to at least launch the debugger by running in a shell that has the venv activated (using poetry shell). But, whenever I try setting breakpoints I get a Server disconnected error, this is the log:

D+00004.256: Client[1] --> {
                 "seq": 5,
                 "type": "request",
                 "command": "setBreakpoints",
                 "arguments": {
                     "lines": [
                         8
                     ],
                     "source": {
                         "path": "/home/delucca/src/delucca/sandbox/poetry-debug-issue/poetry_debug_issue/__init__.py",
                         "name": "__init__.py"
                     },
                     "sourceModified": false,
                     "breakpoints": [
                         {
                             "line": 8
                         }
                     ]
                 }
             }

D+00004.257: /handling #5 request "setBreakpoints" from Client[1]/
             Client[1] <-- {
                 "seq": 11,
                 "type": "response",
                 "request_seq": 5,
                 "success": false,
                 "command": "setBreakpoints",
                 "message": "Server[1] disconnected unexpectedly"
             }

E+00004.266: /handling #5 request "setBreakpoints" from Client[1]/
             Handler 'Client.request' (file '/home/delucca/.python-venvs/lib/python3.10/site-packages/debugpy/adapter/components.py', line 134)
             couldn't handle #5 request "setBreakpoints" from Client[1]:
             Server[1] disconnected unexpectedly

Any ideas of what can I do?

I tried opening the issue on Poetry's repo, but they aren't very helpful.