Setting pythonPath with ${workspaceFolder} in launch.json configs doesn't work

[koenlek]

When I set e.g. this in a config of my workspace's launch.json:

 "pythonPath": "${workspaceFolder}/build/my/own/python",

I get an error about the pythonPath being invalid when I try to run it. As soon as I replace it with the full path it works fine, e.g.

 "pythonPath": "/home/myusername/my_workspace/build/my/own/python",

Note that it works fine with my workspace's settings.json with:

"python.pythonPath": "${workspaceFolder}/build/my/own/python",

I happen to use a custom interpreter and I actually have a variety of workspace folders that draw their settings from a same template for my .vscode settings, so it would be great it we could get the variable to work...

I'm using Ubuntu 18.04, with latest vscode (1.46.0). For anyone trying to debug this: I guess it can be easily reproduced by symlinking your system's python into a folder under your workspaceFolder.

Environment data

• VS Code version: 1.46.0
• Extension version (available under the Extensions sidebar): 2020.5.86806
• OS and version: Ubuntu 18.04
• Python version (& distribution if applicable, e.g. Anaconda): 2.7.17 64-bit
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): custom
• Relevant/affected Python packages and their versions: N/A
• Relevant/affected Python-related VS Code extensions and their versions: N/A
• 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?
• Value of the python.languageServer setting: not set

Expected behaviour

I expect that setting this in my launch.json works:

 "pythonPath": "${workspaceFolder}/build/my/own/python",

Actual behaviour

It doesn't work. But a full path works fine so it seems the variable is not being resolved:

 "pythonPath": "/home/myusername/my_workspace/build/my/own/python",

Steps to reproduce:

Just make a symlink into your workspace to python:

cd to/you/workspace
ln -s $(which python) 

Then create a debug config with:

 "pythonPath": "${workspaceFolder}/python",

Then try to run that debug config

[karrtikr]

@koenlek This is to notify that we can confirm the bug, thanks. As a workaround, if you want to use the workspace pythonPath setting in launch.json, you can just use,

"pythonPath": "${command:python.interpreterPath}"

Please let me know if that works for you. If not, please paste the error logs you see on developer tools.

[koenlek]

@karrtikr, unfortunately, that doesn't work. It gives an error "The Python path in your debug configuration is invalid" once I try to run it. I just feel like any variable expression (e.g. ${...}) under "pythonPath" doesn't work...

[karrtikr]

That's weird, can you please check the values supported for the property "pythonPath"?
You can do that in some new launch.json task, adding the property key and then trying to add a value. You should see which options are available

[koenlek]

Found it! There was a small typo in your suggestion.

// Correct
"pythonPath": "${config:python.interpreterPath}"
// Though your suggestion was:
"pythonPath": "${command:python.interpreterPath}"