No support for per-subpackage launch.json + in monorepo: debugger breaks imports that terminal run resolves

[chirag127]

Environment

• OS: Windows 11 Enterprise
• VS Code: 1.104.x
• debugpy: latest (1.8.x)
• Python: 3.11
• Repo layout: monorepo with src/ layout; each sub-package at packages/<name>/src/<name>/
• Shell: PowerShell

Problem

In a monorepo with a src/ layout, running python -m packages.api.main from the workspace root works in a terminal (with PYTHONPATH=packages/api/src). But when launching the same target via VS Code's debugger ("module": "packages.api.main" in launch.json), debugpy prepends its own path manipulation that:

1. Overrides PYTHONPATH in the subprocess environment.
2. Sets cwd to the workspace root unless explicitly overridden.
3. Does NOT pick up per-folder python.defaultInterpreterPath or env activation from a subfolder .vscode/settings.json.

Result: imports that resolve in a terminal fail in the debugger with ModuleNotFoundError, because debugpy's path injection shadows the manually set PYTHONPATH.

Steps to Reproduce

1. Monorepo: C:\D\workspace\packages\api\src\api\__init__.py
2. launch.json:

   {
     "type": "python",
     "module": "api.main",
     "cwd": "${workspaceFolder}/packages/api",
     "env": { "PYTHONPATH": "${workspaceFolder}/packages/api/src" }
   }

3. Terminal run: cd packages/api && python -m api.main — works.
4. F5 debug: ModuleNotFoundError: No module named 'api'.

Expected

• debugpy should merge the user-specified env.PYTHONPATH with (not replace) its own injected paths.
• Or: document precisely which env vars debugpy overwrites so launch.json authors can compensate.

Related

• Nested subprocess python -m ... fails module resolution only when parent is launched via debugpy #2002 (nested subprocess module resolution) — same root cause, different trigger path

[rchiodo]

I believe the expected way to handle this is to create a launch.json in the subfolder.

Then you'd just debug the packages/api/src/main file directly from the launch.json at packages/api/.vscode/launch.json

[rchiodo]

That works for me if you add the subfolder as a top level folder in the workspace.

Here's what it looks like with the two launch.json files:

Otherwise you could instead set your env.PYTHONPATH to whatever debugpy has set by printing it at the start of test file.