"Error displaying widget" using Jupyter Lab 1.0.2

Possibly related to #124, I am trying to run a super simple example after following the installation instructions:

pip install ipympl

# If using JupyterLab
# Install nodejs: https://nodejs.org/en/download/
jupyter labextension install @jupyter-widgets/jupyterlab-manager
jupyter labextension install jupyter-matplotlib

nodejs info:

$ node -v
v10.16.0
$ npm version
{ npm: '6.9.0',
...
}

Jupyter info:

$ jupyter --version
jupyter core     : 4.5.0
jupyter-notebook : 6.0.0
qtconsole        : not installed
ipython          : 7.6.1
ipykernel        : 5.1.1
jupyter client   : 5.3.1
jupyter lab      : 1.0.2
nbconvert        : 5.5.0
ipywidgets       : 7.5.0
nbformat         : 4.4.0
traitlets        : 4.3.2

Simple example:

# Enabling the `widget` backend.
# This requires jupyter-matplotlib a.k.a. ipympl.
# ipympl can be install via pip or conda.
%matplotlib widget
# aka import ipympl
 
import matplotlib.pyplot as plt
 
plt.plot([0, 1, 2, 2])
plt.show()

Error:

Error displaying widget

Not sure what else I need, or where a version mismatch is, any help is appreciated. Thank you!

[marcel-goldschen-ohm]

The above worked for me with one addition (note that I did not do this in a new fresh environment). I ended up running $ jupyter lab build before everything worked.

Also a note to others that may be getting tripped up with this. I previously thought I had the latest ipympl because conda update ipympl said it was already up to date. However, the version was < 0.4.0 because it was not from the conda-forge channel. Make sure to check the version number as @davidfokkema mentioned above.

Finally, I’m sure everyone agrees, but this really needs to be made much more seamless. Without nice plots jupyterlab is pretty lacking.

[davidfokkema]

I could get it only to work using ipympl 0.4.0 and jupyter-matplotlib 0.5.0. Curiously, updating ipympl actually downgraded my jupyter-matplotlib extension and I had to run labextension update TWICE to get it from 0.4.0 -> 0.4.1 -> 0.5.0. Strange. So, this worked for me (starting from a previous installation):

$ conda install ipympl=0.4.0
$ jupyter labextension update --all
$ jupyter labextension update --all
$ jupyter labextension list
JupyterLab v1.2.4
Known labextensions:
   app dir: /Users/david/anaconda3/envs/labplot/share/jupyter/lab
        @jupyter-widgets/jupyterlab-manager v1.1.0  enabled  OK
        jupyter-matplotlib v0.5.0  enabled  OK

Since ipympl 0.4.0 is in conda-forge, a minimal fresh installation can be (currently) created with:

$ conda create -n labplot -c conda-forge python=3 jupyterlab ipympl nodejs
$ conda activate labplot
$ jupyter labextension install @jupyter-widgets/jupyterlab-manager jupyter-matplotlib
$ jupyter labextension update --all