Native Notebooks - Error loading preloads: Cannot read property 'src' of null

Environment data

• VS Code version: 1.51.0-insider
• Extension version (available under the Extensions sidebar): v2020.11.311084263-dev
• OS and version: Darwin x64 19.6.0
• Python version (& distribution if applicable, e.g. Anaconda): 3.8.6, conda
• Type of virtual environment used : Conda
• Relevant/affected Python packages and their versions: Altair=4.1.0
• Relevant/affected Python-related VS Code extensions and their versions: XXX
• Value of the python.languageServer setting: pylance

With the new Native Notebook and default “Jupyter Notebook Renderer”, I’m getting some error’s when trying to view plots as pngs, with both R/ggplot and Python/altair.

• Altair: if I change the render from ‘mimetype’ (png) to html the chart outputs fine.

• R/ggplot: the chart will display if I change to the builtin png renderer.

Expected behaviour

Chart output png images are displayed.

Actual behaviour

Error loading preloads: Cannot read property ‘src’ of null

Steps to reproduce:

import altair as alt
import pandas as pd

# doesn't work with png
alt.renderers.enable('mimetype')

# does work with html
# alt.renderers.enable('html')

source = pd.DataFrame({
    'a': ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I'],
    'b': [28, 55, 43, 91, 81, 53, 19, 87, 52]})

alt.Chart(source).mark_bar().encode(
    x='a',
    y='b')

Logs

attached native notebook png output issue.txt

[jaymegordo]

@DonJayamanne In the screenshots I added, you can see the text “Select output mimetype to render for current output”.

For R cells only, I wanted to see if I could switch the default from “Jupyter Notebook Renderer” (doesn’t work) to “built-in” (does work), as a temp work around only while this issue is being worked on. Its not a huge deal, was just curious.

In general the new Native Notebooks are amazing though, thanks for all the work you guys put in!!

[DonJayamanne]

Been a few months since this was fixed hence closing this.