Can not insert line breaks in a specific notebook cell

[fuglede]

Unfortunately, I am unable to reproduce this issue, so debugging this seems tricky, but the issue seems major so let me at least try to spell out what I was doing in case that makes it obvious to contributors what could be happening. When I

• created a new Python 3 notebook,
• opened that notebook,
• moved the notebook to another folder,
• inserted the altair snippet below into a cell and executed it,

then I was no longer able to insert line breaks into that cell by pressing return. All other characters could be entered just fine, but adding line breaks was impossible. It is possible, however, to add a line break by copying and pasting one from another cell.

If I copy the contents of the cell to another cell, then that cell works fine, even if I execute the contents. Similarly, if I copy the cell itself (through command mode+C+V), then the newly created cell also works as expected. Likewise, if I add cells above or below the problematic cell, then those also work as expected. Only the initially created cell causes issues.

The code in the problematic cell:

import altair as alt
import json
# Uncomment/run this line to enable Altair in JupyterLab/nteract:
alt.enable_mime_rendering()

# load data as a pandas DataFrame
cars = alt.load_dataset('cars')
cars.to_csv('cars.csv')
chart = alt.Chart(cars).mark_point().encode(
    x='Horsepower',
    y='Miles_per_Gallon',
    color='Origin',
)
d = chart.to_dict()
json.dumps(d)

Some version numbers:

altair                    1.2.1                      py_0    conda-forge
jupyter                   1.0.0                    py36_4
jupyter_client            5.2.2                    py36_0
jupyter_console           5.2.0            py36h6d89b47_1
jupyter_core              4.4.0            py36h56e9d50_0
jupyterlab                0.31.12                  py36_1    conda-forge
jupyterlab_launcher       0.10.5                   py36_0    conda-forge
vega                      0.4.4                    py36_1    conda-forge

[lukeolson13]

This happens to me as well, although I haven't been moving notebooks to different folders. I notice it sometimes when I "Restart Kernel and Clear Outputs...".

[fuglede]

I am still not able to reproduce this consistently but just had it happen again. Hopefully this isn't a red herring, but this time it occurred after clicking shift+tab to produce a tool-tip for a function, and clicking away from the active cell to some other cell.

[jasongrout]

@fuglede - are you on current jupyterlab now? 0.34.12?

[fuglede]

@jasongrout I believe this was in 0.34.1; are there any changes in the most recent versions that could affect this? In any case, I've now made sure to update to 0.34.9 (which seems to be the most recent one available through conda) and will continue to have an eye on it.

Edit: Just noticed that 0.34.12 is in conda-forge, so let me go with that one instead.

[mgab]

I experience this bug, too, but I cannot reproduce it consistently. Some cell stops accepting newline characters (although they can be introduced by copy pasting). Copying the content of the cell into a new cell (or even copying the whole cell with c and v) produces a correctly functioning cell. No moving notebooks around in my case. Closing the notebook tab and opening it again seems to fix the behaviour.

I'm using Jupyter 4.4.0 with jupyter lab 0.35.4, installed with conda 4.5.11.

Does anyone have any idea of some more information that could be useful?

[jasongrout]

Do you have any custom keyboard shortcuts?

[fuglede]

A few in Windows but not in Firefox/Jupyter.

[jasongrout]

Are there any javascript console errors when you notice the misbehavior?

Can you reproduce it when running in incognito mode with no browser extensions? Sometimes a browser extension will interact in weird ways with content on the page.

[mgab]

Do you have any custom keyboard shortcuts?

No custom keyboard shortcuts in my case.

Are there any javascript console errors when you notice the misbehavior?

I'll check it next time I experience the cell misbehavior.

Can you reproduce it when running in incognito mode with no browser extensions?

The problem occurs from time to time and I wasn't able to reproduce it in a controlled manner. Thus, I haven't managed to test it in a controlled environment. I also have a few jupyterlab extensions installed. I have already disabled them, I guess I don't need to uninstall them, right?

[jasongrout]

Disabling the extensions should be enough.

[fuglede]

No JupyterLab extensions here.

[gaurav-kaushik]

I have jupyterlab==0.35.4 with no extensions installed. Return/Enter will stop working in random cells. Restarting kernels does not fix the issue. Moving the notebook, however, does. I don't get this issue with Jupyter Notebooks (i.e. w/o Lab).

jupyter==1.0.0
jupyter-client==5.2.3
jupyter-console==5.2.0
jupyter-contrib-core==0.3.3
jupyter-contrib-nbextensions==0.4.0
jupyter-core==4.4.0
jupyter-highlight-selected-word==0.1.0
jupyter-latex-envs==1.4.4
jupyter-nbextensions-configurator==0.4.0
jupyterlab==0.35.4
jupyterlab-launcher==0.10.5
jupyterlab-server==0.2.0
jupyterthemes==0.18.3

[cbuhl]

I can consistently reproduce this behavior, by starting a string with autocompletion (fx a directory path), and while the suggestions are still open, pressing Shift+Enter. I am on a Mac.

MWE description:
Start a string in a cell with '.
Begin the string with a ~ and the /.
Press TAB, and have a small selection of various directories show up.
Press SHIFT+ENTER, without selecting any of the options.

Now the cell does not insert line breaks when pressing ENTER.
This also works in incognito mode.

[fuglede]

Yep, I can verify that this also produces the issue consistently here. Brilliant!

[ian-r-rose]

Yep, I can reproduce as well. Thanks for the report @fuglede, as well as the nice exampel @cbuhl! I think I will try to fix this as part of fixing #2360, which is also in the works.