ValueError: Transform failed with error code 1: Failed to serialize document: Uncaught

[wdecoster]

Related issue: wdecoster/NanoPlot#207

A user reported an error coming from kaleido, the relevant part of the traceback is below:

    f.write(scope.transform(self.fig, format="png"))
  File "/home/user/.local/lib/python3.8/site-packages/kaleido/scopes/plotly.py", line 110, in transform
    raise ValueError(
ValueError: Transform failed with error code 1: Failed to serialize document: Uncaught

The code is:

scope = PlotlyScope()
with open('output.png'), "wb") as f:
    f.write(scope.transform(fig, format="png"))

It could be that the image is rather large, would that explain the problem? What can I do to debug?

Thanks,
Wouter

[jonmmease]

Hi @wdecoster, thanks for the report. There is an open issue for figures that are "too large" (#19) but that results in a particular error that's different that what you're seeing.

My first question would be whether this happens with even small simple figures.

---

Here's one guess. When you build the PlotlyScope using the default constructor, Kaleido uses an online CDN location for the plotly.js bundle. So if the user doesn't have internet access (or is behind a proxy/firewall) then this kind of error could occur.

The plotlyjs argument/property to PlotlyScope can be used to point Kaleido to a local plotly.js bundle, which is what plotly.py does. If you're comfortable requiring plotly >= 4.9, then I would actually recommend letting plotly.py take care of interacting with kaleido, replacing what you have with

import plotly.io as pio
pio.write_image(fig, "output.png", engine="kaleido")

If you need to support older versions of plotly.py, then you could copy the kaleido initialization logic from

https://github.com/plotly/plotly.py/blob/8289eb1c85125e147c4ce14b56272ed50b99ef20/packages/python/plotly/plotly/io/_kaleido.py#L9-L17

which will configure the PlotlyScope to use the plotly.js bundle that is included with plotly.py.

[wdecoster]

Great, thanks for the pointers. I'll make some changes and test that. It seems indeed to be the case that the user doesn't have internet access on this machine.

[nehaljwani]

I hit the same issue and copying the init logic worked in my case.

[jonmmease]

@wdecoster, have you had a chance to try this?

[wdecoster]

Sorry for the lack of feedback, I hope to get back to this next week.

[wdecoster]

I made the changes you suggested (pio.write_image(fig, "output.png", engine="kaleido")), and at least a test where I unplugged my ethernet cable worked with the changes (but not without). I expect this also to fix the problem for the user who initially reported the error.

Thanks!

[jonmmease]

Great! Just make sure to update your minimum plotly.py version requirement to plotly>=4.9.0.

edit: Never mind, I see that you did in wdecoster/NanoPlot@9c840b7

[wdecoster]

Took care of that, but thanks for the warning ;-)