Code finishes fully executing after 'Disconnect' / Shift-F5 / terminate debugging

[karthiknadig]

Discussed in microsoft/vscode-python#24205

^{Originally posted by PeterMuhlberger September 28, 2024}
I recently ran into this: While doing a little step-through debugging with the vscode Python Debugger (extension), I tried to terminate the debugger by pressing the icon to disconnect the debugger. Instead of ending with a KeyBoardInterrupt as usual, the code after the breakpoint ran completely, creating quite a mess. The same problem occurs if I use Shift-F5, but not when I use the small square that terminates cell execution. I've tried a wide range of possible fixes to the problem, but it persists.

Before going any further, I should ask if this is the right place to report this problem and whether I should report it directly to Issues here? Beyond this: has anyone else run into this? Any suggested solutions?

(I've tried, among other things: Reinstalling my Python and Jupyter extensions; installing 2 month old versions of these extensions (before this problem started happening); disabling other extensions; inserting the default launch.json file in my workspace; trying to see if the problem occurs in a new notebook file outside the workspace I encountered the problem initially (it does); checking if setting the breakpoint above the initial line still causes continued code execution (it does); looking for potentially problematic lines in settings.json (saw none)).

[PeterMuhlberger]

Thanks Karthik and Kacie! Need anything else from me? It may help to know that I'm using MX Linux, current stable. I could provide more details about hardware / software. In terms of reproduction, it reproduces perfectly on my computer--the problem always occurs. Of course, you're probably thinking of reproduction by someone else.

[rchiodo]

Are you doing this in a notebook? Stop debugging does something different depending upon how you're debugging something.

In a jupyter notebook, it sends a keyboard interrupt (or interrupt kernel). But based on where you are in the cell, it might not handle the interrupt and just keep going.

In a regular python file if you launched the program with the debugger, stop debugging will just kill the process. If you attached to the program, it will detach, but the process will continue to run.

[PeterMuhlberger]

Thanks rchiodo: Yes, I'm doing this in a jupyter notebook. I never had this problem before: terminating the debugger always stopped subsequent code from being executed. I think the problem started after a recent vscode update. It doesn't seem to matter where I am in a cell--it always continues execution. I tried creating a new notebook with a very simple print function in one cell and a 2nd cell with one line that called that function. I put the breakpoint on that line. When I terminated the debug, the print executed--indicating that lines continued to run after termination. I've also replicated this bug in multiple places in more complex code. The one thing I've thought of that I haven't tried yet is to reinstall vscode--in part because I had reinstalled it recently.

[rchiodo]

That has entirely to do with the kernel itself though. You can verify this by just running a cell that calls say some C++ code that sits there forever. You can't interrupt it. Sometimes a keyboard interrupt doesn't work.

We should double check with the jupyter team though, maybe they recently removed the keyboard interrupt. I could be wrong but the jupyter extension used to interrrupt the kernel on the detach.

[rchiodo]

@DonJayamanne @amunger is that your recollection as well? Debug detach should interrupt the kernel? Maybe I'm remembering wrong.

[amunger]

I'm pretty confident that nothing changed there on the Jupyter extension side recently.
I'm still able to stop a debugging cell with interrupt while at a breakpoint:

[PeterMuhlberger]

By way of comparison, here is what I see. A break at the breakpoint, ask to terminate, and it executes the function

[rchiodo]

@amunger do you know where the kernel.interrupt is fired from? Or are you saying you hit the 'interrupt' button?

[amunger]

I'm using the interrupt button, yes, which causes core to call the interrupt handler on the controller and jupyter sends an interrupt to the kernel https:/microsoft/vscode-jupyter/blob/4151b43c83be7e4f2ebca5e0958d06100d490cac/src/notebooks/notebookCommandListener.ts#L139

[rchiodo]

Okay so maybe I'm wrong, maybe we never had debug automatically do an interrupt. The user has to pick that option explicitly. Make sense now that I think about it.

You might have started debugging in order to debug the first part of the cell, but you want it to continue and you don't care about debugging anymore.

If you want it to stop debugging, you hit the interrupt button.

[rchiodo]

@PeterMuhlberger if you want it to interrupt execution, you have to explicitly click the 'interrupt' button.

[PeterMuhlberger]

Hi rchiodo: For my 2 bits: I am talking about the Disconnect button (or, alternatively, Shift-F5) on the debugging tools palette that appears. These in the past ended code execution from what I can recall (I remember seeing keyboard interrupt messages after using that button). If I wanted the code to continue executing, there is the Continue or F5 button. What you're saying is that now I need to go back to the cell at which I started debugging, which can be quite far from the break point, and use the Stop Cell Execution square to the left. That's do-able, but seems awkward.

[rchiodo]

There should also be an 'interrupt' button at the top of the notebook too.

You can also suggest a feature request on the jupyter extension to have debug detach automatically do an interrupt.

[PeterMuhlberger]

Thanks rchiodo! I've avoided that interrupt button in the past because I imagined it might restart the kernel, but it doesn't.