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

EDIT: See microsoft/vscode#161498 for resolution.

Environment data

• debugpy version: 1.6.3
• OS and version: CentOS 7.9, macOS 11.6.2 (Big Sur)
• Python version : Tested on 3.9 (macOS), 3.7 and 3.6 (CentOS)
• Using VS Code or Visual Studio: VS Code

Actual behavior

In VS Code, 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 a more complex example that I couldn't find a MWE for, the Call Stack pane in VS Code says:

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

Expected behavior

Breakpoint is hit and the path-mapping works.

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")

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"

Attach via the debugger.

[fabioz]

Actually, debugpy itself does everything properly here, it's VSCode itself that doesn't support it.

i.e.: the stack frame message is correct:

{"type": "response", "request_seq": 19, "success": true, "command": "stackTrace", "body": {"stackFrames": [{"id": 2, "name": "<module>", "line": 15, "column": 1, "source": {"path": "//tmp/vscode-path/vscode_blah.py", "sourceReference": 1}}, {"id": 3, "name": "<module>", "line": 1, "column": 1, "source": {"path": "<string>", "sourceReference": 2}}], "totalFrames": 2}, "seq": 48, "pydevd_cmd_id": 502}

So I'm closing this here because it can't be fixed by debugpy as the issue is in the VSCode client side.

Paul Kilgo (@OEP) can you report this to https://github.com/microsoft/vscode/issues?

Screenshot showing error: