nbsphinx compatability with `mathjax3_config['options']['processHtmlClass']` override

Describe the bug

Yesterday myst parser updated and now warns:

WARNING: `mathjax3_config['options']['processHtmlClass']` is being overridden by myst-parser to tex2jax_process|mathjax_process|math. Set `myst_mathjax_classes = None` if this is undesirable.

Setting `myst_mathjax_classes = None`` as per instruction does not work, and generates another batch of warnings:

WARNING: The config value `myst_mathjax_classes' has type `NoneType', defaults to `str'.
WARNING: myst configuration invalid: 'mathjax_classes' must be <class 'str'> (got None that is a <class 'NoneType'>).
WARNING: `mathjax3_config['options']['processHtmlClass']` is being overridden by myst-parser to tex2jax_process|mathjax_process|math. Set `myst_mathjax_classes = None` if this is undesirable.

The docs explain something here. I tried also update_mathjax=False and setting values for myst_mathjax_classes=...

Expected behavior

No warning, or a solution to fix the underlying reason why it gets shown.

Environment

• Python Version [e.g. 3.7.1]: 3.8
• Package versions or output of jupyter-book --version: x
• Operating System: macos

Additional context

It is not possible to downgrade to 0.14.0 or sphinx gets uninstalled. Why?

[chrisjsewell]

And yes it seems we have nbsphinx too

yeh I’ll blame that all on nbsphinx then lol, but I’ll have a look at making a change to accommodate it

I tried also update_mathjax=False

Note this should be myst_update_mathjax=False, that should work (although maybe not recommended)

[chrisjsewell]

Heya, can you confirm that you do not have any specific configuration for mathjax in your conf.py?

It is not possible to downgrade to 0.14.0 or sphinx gets uninstalled. Why?

It is possible to downgrade; it will also downgrade to sphinx 3, because 0.14 does not support sphinx 4 but should not just uninstall it entirely. If you have any different behaviour, I would raise this with the dependency manager you are using (e.g. pip/conda)