Modules with two leading slashes can't be mapped properly in VS Code debugger

[OEP]

Hi, this is a follow-up to a discussion (microsoft/vscode-python#19835). I reported to debugpy (#1061), it was reproduced there, and they referred me to the main repo (microsoft/vscode#161498). They've asked me to report here.

EDIT: See microsoft/vscode#161498 for resolution.

Behaviour

When a module has two slashes in its path, the path mapping in the debugger does not seem to work.

Expected vs. Actual

In VS Code, the breakpoint is hit, but path-mapping does not work with an error in the editor pane.

The editor could not be opened because the file was not found.

Creating the file tries to mkdir /vscode-path and fails.

In some cases I have also seen this error in the Call Stack pane.

[UriError]: If a URI does not contain an authority component, then the path cannot begin with two slash characters ("//")

I was expecting the path mapping to work since two leading slashes is technically an OK path on Linux and macOS.

Steps to reproduce:

Create a file like the following:

$ cat /tmp/vscode-path/vscode_blah.py 
import sys
import pprint
pprint.pprint(sys.path)

import debugpy
debugpy.listen(5678)
print("WAIT")
debugpy.wait_for_client()

print("HEY")

Set a breakpoint on that final print().

Create a standard "remote attach" debug configuration.

{
        "host": "localhost",
        "name": "Remote Attach",
        "port": 5678,
        "request": "attach",
        "type": "python"
}

In the VS Code editor, set a breakpoint on the final print().

Try to import it via a PYTHONPATH with a leading double slash.

$ PYTHONPATH=//tmp/vscode-path python3 -c "import vscode_blah"

Use the Remote Attach configuration to try and debug the process.

Diagnostic data

• Python version (& distribution if applicable, e.g. Anaconda): 3.9.12
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Global
• Value of the python.languageServer setting: Default

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

Experiment 'pythonTensorboardExperiment' is active
Experiment 'PythonPyTorchProfiler' is active
LSP Notebooks experiment is disabled -- Jupyter does not support experiment
> conda info --json
Python interpreter path: /usr/local/bin/python3
> /usr/bin/python ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/get_output_via_markers.py ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/interpreterInfo.py
> /usr/bin/python3 ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/get_output_via_markers.py ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/interpreterInfo.py
> /usr/lib/python2.7 ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/get_output_via_markers.py ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/interpreterInfo.py
> /usr/local/bin/python3 ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/get_output_via_markers.py ~/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/interpreterInfo.py
[ERROR 2022-8-22 20:25:55.856]: Error: Command failed: /usr/lib/python2.7 /Users/pkilgo/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/get_output_via_markers.py /Users/pkilgo/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/interpreterInfo.py
/bin/sh: /usr/lib/python2.7: is a directory

    at ChildProcess.exithandler (node:child_process:408:12)
    at ChildProcess.emit (node:events:526:28)
    at maybeClose (node:internal/child_process:1092:16)
    at Socket.<anonymous> (node:internal/child_process:451:11)
    at Socket.emit (node:events:526:28)
    at Pipe.<anonymous> (node:net:687:12) {
  killed: false,
  code: 126,
  signal: null,
  cmd: '/usr/lib/python2.7 /Users/pkilgo/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/get_output_via_markers.py /Users/pkilgo/.vscode/extensions/ms-python.python-2022.8.1/pythonFiles/interpreterInfo.py'
}
Starting Pylance language server.
Connecting to DAP Server at:  localhost:5678

User Settings

languageServer: "Pylance"

[fabioz]

I see you're doing the roundtrip there ;)

I've just commented on microsoft/vscode#161498 (comment) why I think the issue is on VSCode itself.

[karthiknadig]

This should be then re-open on VS Code itself. Python extension is not involved here. This is handled by DAP client.

[karthiknadig]

Reopened it: microsoft/vscode#161498