Debug configuration env variables should overwrite env variables defined in .env file

[ccrvlh]

Environment data

• VS Code version: 1.58.2
• Extension version (available under the Extensions sidebar):
• OS and version: MacOS 11.4
• Python version: 3.8.10
• Type of virtual environment used: venv
• Relevant/affected Python packages and their versions: Flask
• Value of the python.languageServer setting: "Default"

Expected behaviour

"env" portion of launch.json doesn't seem to work.
When trying to launch a Flask application I have the following tree structure:

/.venv
/.vscode
/app
-- uwsgi.py ---> Flask Application

My launch.json file is:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Python: Flask",
      "type": "python",
      "request": "launch",
      "module": "flask",
      "pythonPath": "${workspaceRoot}/.venv/bin/python",
      "env": {
        "FLASK_APP": "app/uwsgi.py"
      },
      "args": ["run"],
      "jinja": true
    }
  ]
}

When running the debugger Flask says it can't find application and the first line shows:

* Serving Flask app "application.py"

So from what I can understand it is as if the env var "FLASK_APP=app/uwsgi.py" is not being read, so it loads the default "application", and can't find the app.

Tried without the debugger and works fine (FLASK_APP=app/uwsgi.py; flask run).

Another weird thing is that when I set

      "env": {
        "FLASK_APP": "app/uwsgi.py",
        "FLASK_ENV": "development"
      },

it goes as for as running the server, but when trying to reach any endpoint it says flask.cli.NoAppException: Could not import "application"..
If I remove the FLASK_ENV line it doesn't even run the server and gives me an error: Error: Could not import "application".

[fabioz]

@lowercase00

The way you're defining things, I think your "cwd" must be at a pretty specific place for app/uwsgi.py to be picked up, yet, you're not defining it... can you try to specify the "cwd" in the launch config to be the folder which contains app/uwsgi.py to see if it works?

Note: it did work for me when the cwd was properly specified...

[ccrvlh]

@fabioz thanks, I did try with ${workspaceFolder} before the app/uwsgi.py also didn't work, I'll try setting cmd to set how it goes

[ccrvlh]

Just tried with cmd and also didn't work.
What I find weird is the application. Is not that is not finding the Flask App, it's not even looking for app/uwsgi.py is only looking for application.py as if the env var is not being read.

[ccrvlh]

Weird enough, I can't replicate the issue on a newly create Flask project with exactly the same folder structure. I've already created and recreated the venv and everything else that I could (mypy, pyenv, vscode folder etc). Any tips ou troubleshooting this? I've got no messages at all at the developers console, so really no idea what could be the issue.

[int19h]

Are there any version differences in the packages between the two environments, if you look inside .venv/site-packages?

[ccrvlh]

So finally found out the issue. I had an old FLASK_APP=application.py on my .env file, and it was overwriting the env vars I was passing in the launch.json. I'm not sure if it's possible for the extension to control the order in which env vars are loaded, so not sure if anything different could have been done. If it is, I would suggest that the env vars in the launch.json file to be top priority and overwrite other env vars, instead of the other way around.

[int19h]

From debugpy perspective, it doesn't actually know anything about .env - that's something the extension handles, basically, by reading the file and then injecting those variables into your debug config. So this would need to be handled in vscode-python.

But I agree that launch.json should take priority - .env is supposed to define the default values for the entire folder/workspace, but individual debug configurations should be able to override that as needed.