I can reproduce this, but only if the debug console panel is moved right, not bottom.

I am also running into this.

Possibly related: #70331

• VSCode Version: 1.37.1
• OS Version: Ubuntu 18.04.3 LTS

Steps to Reproduce:

1. Create a new Python project (requires numpy)
2. Add the code:

import numpy as np
x = 5

3. Place a breakpoint on x=5
4. Run the code, allow the breakpoint to be hit.
5. In the debug console type: np.ones((720,1))
6. In the debug console type: 4+4
7. Observe that the scroll returns to the top of the debug console

Does this issue occur when all extensions are disabled?: Yes

@JoshVarty nice steps. Thanks. I plan to look next week into this.

I can not reproduce this with node, even though I have multiple lines that wrap.
Unfortunetly I do not have pyhton setup on my machine to follow the exact python steps (after doing pip install numpy I get an exception when debugging the program No module named 'numpy')

I believe the issue is here

I am open for a PR which fixes this.
The solution would be to better aproximate the height based on the value length.
Due to this bad approximation the autoscrolling breaks.

Nope, this works for me

@isidorn

The line doesn't wrap around because the output is trimmed. You might want to try this instead:

'-'.join([str(i) for i in range(2000)])

Also I can only reproduce with the debug panel on the right (Right click > Move panel right).

I can't reproduce the problem with that python line above though. It do with the steps here #79213 (install Python extension, start debug session, move panel to right)

In trying to come up with a numpy-free set of repro steps (I failed), I noticed something unexpected. In the Python stand-alone console, numpy.ones((5,1)) outputs

array([[1.],
       [1.],
       [1.],
       [1.],
       [1.]])

while in the Debug Console, it outputs

array([[1.],\n       [1.],\n       [1.],\n       [1.],\n       [1.]])

The same is not true for some other non-numpy multiline-output, such as the one from print("a\nb"), which is shown in two lines in both cases. Also, commands such as print(str(numpy.ones((720,1)))) (note the extra str) do not cause this issue.

Based on this, consider the following hypotheses (speculative, but nevertheless):

1. This is a numpy-specific problem, so @isidorn might have a hard time reproducing it without setting up numpy in his Python environment.
2. VS Code uses a correct internal rendering of the output to estimate its height, but the actual output has a lower height due to \n being printed instead of converted into line breaks. This causes a height mismatch somewhere, leading to incorrect vertical scroll positions. This is somewhat supported by the "Copy All" command in the Debug Console copying line breaks, not \n characters.

Point 2. makes sense. However this is not only specific to numpy, but to a particular type of output.

I think it has something to do with Python's __repr__ (which might mean this isn't a VSCode bug, but a Python tools bug?)

I believe __repr__ creates a representation of a Python object for use in things like debuggers.

Anyways, I've got a numpy-free repro for you:

1. Create a new Python project
2. Add the code:

class Test:
    def __repr__(self):
        return "\n\t" * 10000
x = Test()

y = "this line is for your breakpoint"

3. Place a breakpoint on y = "this line is for your breakpoint"
4. Run the code, allow the breakpoint to be hit.
5. In the debug console type: x
6. In the debug console type: 4+4
7. Observe that the scroll returns to the top of the debug console

What's interesting is that if you create x="\n\t" * 10000 and then observe x in the debug console, you'll notice that it prints the value of x properly and has no problems with any subsequent commands in the debug console.

This only seems to reproduce for me within the context of __repr__.

Can you all reproduce this with the debug console panel to the bottom? I can only when it's to the right.

Here are my steps to reproduce:

1. Run command ext install ms-python.python
2. Open this extension sample folder in vscode
3. Start debugging session (F5)
4. Open debug console on host
5. Move it to the right
6. Open a python file in the guest

And observe the scrolling problem.

This forces me to have the debug console at the bottom while developing an extension.

@JoshVarty thanks for awesome repro steps. I can repro now, investigating...

Thanks! 🎉

I verified using the nice steps here: #77837 (comment)
I'm still seeing scroll return to the top of the console.

Let's keep this closed since there is already a duplicate which I will look into next milestone.
Though it should behave a bit better now
Duplicate #81951 (comment)

Actually my fix just made it worse. Sorry about that. Reverting my fix and reopening this issue.
This milestone I will fix this proper, promise 🙏

@jeanp413 contributed a cool fix for this, thanks a lot!

Can people please try this out in vscode insiders from Tuesday and let us know if it is better for you. Thanks a lot!

@jeanp413 The fix is working. I now have the desired scroll behaviour back! @jeanp413 and @isidorn Thanks a lot!

Thanks, adding verified label.