Debugging via -m does not work when the target is a package

[brettcannon]

[Found by CTI]

Environment data

• PTVSD version: Whatever is in 2018.10.0-beta
• OS and version: N/A
• Python version (& distribution if applicable, e.g. Anaconda): N/A
• Using VS Code or Visual Studio: 1.29.0-insider

Actual behavior

Message stating No module named pkg.

Expected behavior

Be able to debug pkg which is a package containing a __main__.py file.

Steps to reproduce:

1. Create a package
2. In that package define a __main__.py
3. Set a breakpoint in that __main__.py
4. Run the package via -m.

[int19h]

We don't handle module (or file) launch ourselves, and just pass it on to pydevd via --module. So it looks like there's an issue on pydevd side of things.

[karthiknadig]

this looks same as #748. @fabioz has left an explanation for that case.

[int19h]

I'm not sure I follow the explanation in that bug. Python 3 can handle -m on namespace packages just fine.

[fabioz]

@int19h @karthiknadig you're right, my fault, sorry about that... I think I tested #748 with 2.7 and not 3.7 and this works in python 3 (and #748 was a valid bug for Python 3 and is only invalid for Python 2).

[brettcannon]

And just to be clear, this isn't just namespace packages but any package where this is a problem.

[karthiknadig]

@fabioz Prioritize this issue over others.

[fabioz]

I just checked here and creating a pkg/__main__.py and doing a launch for pkg did work properly for me...

I investigated a bit more, and having something as pkg/sub/__main__.py and launching pkg.sub failed for me... can you confirm if that's the case for you?

-- I created a pull request fixing the issue I found launching a module with dots in the name (#995), but if launching a module without dots in the name doesn't work for you it may be something different as I was not able to reproduce that.

[DonJayamanne]

Note, this used to work in 2018.9.* version of the Python extension.
Back then PTVSD was launched using -m using the CLI, in the new version of the extension we have a launcher script that invokes the PTVSD api.

Hope this will help narrow down the issue.

[int19h]

I doubt that this matters, because from pydevd perspective it's going to see the same argv in its main both cases, with --module ... corresponding to the module being launched.

[DonJayamanne]

Interesting, how then did it work in the past (older version of the extension with PTVSD 4?
This can only mean its a regression in PTVSD/PyDev.

[brettcannon]

FYI someone ran into this and asked about it on Stack Overflow.

[brettcannon]

And another post about the same issue.

[fabioz]

This should be fixed in master.

[janosh]

@fabioz I'm still having trouble with this. Trying to debug ./src.main.py using the configuration

{
  "name": "Python: Module",
  "type": "python",
  "request": "launch",
  "module": "src.${fileBasenameNoExtension}"
}

only results in the error No module named src.main. Running python -m src.main works fine. Any ideas how to fix this?

[fabioz]

@janosh, can you give details on the file structure you have for your project?

[karthiknadig]

@janosh the fix for this is not in a public release yet. You can try with master for this.

[janosh]

@fabioz If the fix isn't released yet, I guess we can skip troubleshooting.

@karthiknadig Can you estimate how far out the release is?

[karthiknadig]

@janosh I will be making a release likely by this Friday.

[janosh]

@karthiknadig How does the update process work? Does ptvsd update together with VS Code's Python extension?

[DonJayamanne]

Yes

[janosh]

@karthiknadig Thanks for the quick fix! Module debugging works great now.