.ipynb debug cell -- debugger fails to hit breakpoint

[p-i-]

Type: Bug

TLDR (Edited 9 Aug)

In my case the problem was fixed by toggling "Jupyter: Debug Just My Code" in Settings to ON.

Original message ...

I have VSCode opened in $root. I have $root/.venv/... (Python 3.12.3, freshly installed using pyenv (macos))

I create test.ipynb

First cell: a = 1, Second cell: b = 2. I execute the first cell. ok. I set a breakpoint on the first (and only) line of the second cell and debug-execute it.

There's no visual indication the breakpoint has been hit. And attempting to step-{in/out/over} lands me in alien code (see screenshot).

Now I try to create a fresh test case. Quit VSCode, create test/ folder, create test/.venv/ (from pyenv, identically as done per fail-case), open VSCode in test/, create x.ipynb, 2 cells a = 2 and b = 2, execute the first. ok. set breakpoint on second and debug-execute the second.

It hits! It works!

So something in my $root project is mashing the debugger.

This is bizarre and frustrating. It means I'm going to have to copy my entire codebase into a fresh project just to get the debugger working in .ipynb files.

Extension version: 2024.7.0
VS Code version: Code 1.92.0 (b1c0a14de1414fcdaa400695b4db1c0799bc3124, 2024-07-31T23:26:45.634Z)
OS version: Darwin arm64 23.5.0
Modes:

System Info

Item	Value
CPUs	Apple M2 (8 x 2400)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	3, 3, 2
Memory (System)	24.00GB (2.33GB free)
Process Argv	--crash-reporter-id f10d97cd-2115-4dba-a34a-07be9312995a
Screen Reader	no
VM	0%

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[p-i-]

Test case (works):

Fail case (my project):

If I click step {over/out/in} on the fail-case:

[p-i-]

^ That's how I'm invoking debug on a cell

[p-i-]

Here are the TRACE logs for Output -> Jupyter:

FAIL:
fail.txt

WIN:
win.txt

[p-i-]

As a follow-up, this has hit me again.

To resolve it, I created a fresh folder, created a ./.venv, opened VSCode, copied my .ipynb and .py file into this new folder, and was able to successfully use the debugger in my .ipynb.

• Setting breakpoints either in the .ipynb or the .py and debug-running the cell, they would hit.
• I could navigate the call-stack and single-step debug.
• Checking 'raised exceptions' in the "Breakpoints" pane, execution would indeed suspend at the exception, highlighting the offending line, and allowing me to use "Debug Console" pane to inspect.

Then I left VSCode running and went to sleep. And now first thing in the morning, it is again failing.

I haven't done anything fancy. All I've been doing is tweaking a numpy-heavy .py file and an .ipynb that uses it. I haven't done anything else on my mac, other than watch a YouTube video in a Chrome tab.

In fact my "fresh folder" was the folder I used for my working testcase (first screenshot).

And re-executing the test now fails. On exactly the same x.ipynb file!

I've looked through all available logs in Output pane, and see no anomaly.

This is a serious problem :/

[p-i-]

As per https://stackoverflow.com/questions/56794940/vscode-why-isnt-debugger-stopping-at-breakpoints toggling "Jupyter: Debug Just My Code" in Settings to ON has gotten it working.

Why can't I see the setting I just changed in ~/Library/Application\ Support/Code/User/settings.json? Even after a VSCode restart it's not there. And I have no .vscode/ folder in my project. I thought every settings-change creates a new entry at the bottom of this JSON list.

[DonJayamanne]

Than you for filling this issues and sorry you are running into this
And Thank you for your detailed analysis and screenshot

I think the final conclusion would that the settings aren’t getting saved/applied correctly.

Is that correct?

[p-i-]

Let me clarify my last post. There's two complete separate things in it.

1. Toggling "Jupyter: Debug Just My Code" to ON fixes the "debugger not working correctly" issue. Now this is a bizarre fix. So the issue should be considered as a bug IMO.

2. After toggling this setting, I decided to inspect my User/Settings.json so that I could copy down the exact key for this setting, and was surprised to find that the setting isn't getting written to that file. I doubt this is connected to the original issue. But I am curious as to why I can't find this setting. I just checked again today and it is still not there.

[DonJayamanne]

as to why I can't find this setting. I just checked again today and it is still not there.

Default values aren't written into settings.json
By default this value is turn on, hence you may have disabled this at some point in time.

I doubt this is connected to the original issue.

Given that you are not debugging any 3rd party code and just a simple cell and its not hitting your break point.
I agree, that the setting should not really make a difference, however for now I would suggest enabling the value as that is the default value.

[p-i-]

Please someone remove the info-needed tag.

[edervishaj]

I have the same problem, the debugger does not stop. Moreover, after I stop it, the little arrow that allows me to select "Debug Cell" disappears. Tried reverting back to previous versions, both vscode-jupyter and vscode-python extensions, nothing worked.

[p-i-]

I've also bumped into that disappearing debug-cell option.

As I remember, closing and restarting VSCode shakes it loose.

I haven't been able to isolate a clean consistent minimal fail, so I haven't reported that oddity yet.

There are still quite a few quirks with running .ipynbs in VSCode. I wish they had someone on the team that uses .ipynbs a lot -- they would surely bump into these frustration points.

Or even a Discord where if some engineer hits such a problem, a core-dev could remote-inspect their system over screenlink. I'd be more than happy to allow a core-dev to dig around in my box if it would lead to a seamless UX.

[edervishaj]

This is not the only issue I face. After stopping the debugger (because it does not stop) and relaunching it, I get the error "Couldn't find a debug adapter for debug type python". This started occurring after the last update of VSCode/Python extension. I tried downgrading everything, the problem persists.

[p-i-]

@edervishaj Did you try deleting and re-creating your Python .venv? It might be possible that it is corrupted somehow.

[edervishaj]

@edervishaj Did you try deleting and re-creating your Python .venv? It might be possible that it is corrupted somehow.

I created a new environment altogether, did not help at all. The debugger stops but after the first step over it throws the above error.

[DonJayamanne]

After toggling this setting, I decided to inspect my User/Settings.json so that I could copy down the exact key for this setting, and was surprised to find that the setting isn't getting written to that file. I doubt this is connected to the original issue. But I am curious as to why I can't find this setting. I just checked again today and it is still not there.

@p-i- Please can you create a separate issue for this, then we can close this.
Also, when creating a new issue, please can you create the issue in the VS Code repo, as thats un-related to Jupyter extension (its a functionality provided by VS Code itself)

This is not the only issue I face. After stopping the debugger (because it does not stop) and relaunching it, I get the error "Couldn't find a debug adapter for debug type python". This started occurring after the last update of VSCode/Python extension. I tried downgrading everything, the problem persists.

@edervishaj Please can you create a new issue and please do share the following logs in that new issue
Please could you enable logging as follows:

• Open settings & go into Jupyter->Logging
• Change the value to trace
• Reload VS Code,
• Attempt to repro the issue & then copy the output from the Jupyter output panel (use the command Jupyter: Show Output to get to the logs).