Stuck VS Code window when starting RBL when other cells are already running

[roblourens]

• Open the Titanic.ipynb
• Scroll halfway down, on some cell run "Run all cells above" then click the RBL button right away
• I expect to enter RBL mode once the other cells finish executing

The execution would be queued, but we probably attach a debugger at the moment the cell is clicked, and it makes something weird happen.

The error notifications come from the python extension:

https://github.dev/microsoft/vscode-python/blob/49dc58c3c5c4989245a7354aeb362732cb379fa8/src/client/debugger/extension/hooks/childProcessAttachService.ts#L37

Why is the python extension trying to attach? Why is it stuck showing notifications forever? Is it supposed to be involved for some reason? @IanMatthewHuff @DonJayamanne @DavidKutu @karthiknadig does anyone know?

[DavidKutu]

I can't repro this, the expected result happens for me

[roblourens]

I can repro 100% of the time. It's not actually an infinite loop of dialogs, it's like one per cell or something

[DavidKutu]

I can't get it to happen, it might be a mac thing. @IanMatthewHuff and @DonJayamanne could you help us and try to repro this on your macs?

In insiders, build main for jupyter and have the latest python ext (v2021.9.1246542782). Thanks

[IanMatthewHuff]

@roblourens and @DavidKutu I'm not seeing the same thing as either of you (on Mac) for me the run all runs to completion, but then the run by line action never happens. I'm not in a stuck state, but the RBL command seems to have just been chucked if I did it during the run all.

[roblourens]

I get a debugpyAttach event, this comes from debugpy here https://github.dev/microsoft/debugpy/blob/0a3fa3f94dbaeec8c0b8c0defbbfc745e305e82c/src/debugpy/adapter/clients.py#L562-L562. There must be a subprocess spawned somewhere in the course of running the notebook, any idea what that would be?

I think the python extension also should not listen to debug events that came from debug sessions that it does not own.

We start the debug session right away while other cells are executing. I guess to do this right, we would be able to put a callback into the cell execution queue which would let us start RBL at the correct time.

I was able to repro this on my windows machine too.

[greazer]

This bug is moot if we solve #7740.