Math domain regression in Sphinx 8.2.0rc1

[mgeier]

Describe the bug

See https://github.com/mgeier/nbsphinx/actions/runs/13354246486/job/37294757350

$SPHINX doc _build -b html
Running Sphinx v8.2.0rc1
...


Versions
========

* Platform:         linux; (Linux-6.8.0-1021-azure-x86_64-with-glibc2.39)
* Python version:   3.13.2 (CPython)
* Sphinx version:   8.2.0rc1
* Docutils version: 0.21.2
* Jinja2 version:   3.1.5
* Pygments version: 2.19.1

Last Messages
=============

    writing output...

    building [html]: targets for 39 source files that are out of date
    updating environment:
    [new config]
    39 added, 0 changed, 0 removed

    reading sources... [  3%]
    a-markdown-file

Loaded Extensions
=================

* sphinx.ext.mathjax (8.2.0rc1)
* alabaster (1.0.0)
* sphinxcontrib.applehelp (2.0.0)
* sphinxcontrib.devhelp (2.0.0)
* sphinxcontrib.htmlhelp (2.1.0)
* sphinxcontrib.serializinghtml (2.0.0)
* sphinxcontrib.qthelp (2.0.0)
* nbsphinx (0.9.6)
* sphinxcontrib.bibtex (2.6.3)
* sphinx_last_updated_by_git (0.3.8)
* sphinx.ext.autodoc.preserve_defaults (8.2.0rc1)
* sphinx.ext.autodoc.type_comment (8.2.0rc1)
* sphinx.ext.autodoc.typehints (8.2.0rc1)
* sphinx.ext.autodoc (8.2.0rc1)
* sphinx_codeautolink (0.16.2)
* sphinx.ext.intersphinx (8.2.0rc1)

Traceback
=========

      File "/opt/hostedtoolcache/Python/3.13.2/x64/lib/python3.13/site-packages/nbsphinx/__init__.py", line 1473, in apply
        env.get_domain('math').data['has_equations'][env.docname] = True
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
    KeyError: 'has_equations'

How to Reproduce

Build the docs of https://github.com/spatialaudio/nbsphinx with Sphinx 8.2.0rc1.

If needed, I can try to come up with a more minimal example.

Environment Information

see above

Sphinx extensions

Additional context

No response

[AA-Turner]

Caused by the performance improvement in #13044. I had thought we kept the key for backwards compatibility, though.

A

[mgeier]

What I'm trying to do in the line that fails: I want to force the math extension to believe that there are equations on each Jupyter notebook. Otherwise, MathJax wouldn't be loaded and equations wouldn't be displayed correctly.

Is there another way to achieve that?

In the long term, it would probably be better if nbsphinx could check each Jupyter notebook whether it actually uses math equations, but that's a bit more involved (and I would still need a way to signal to Sphinx that MathJax should be activated).

[AA-Turner]

The new method in #13044 is to detect maths by if the visitor methods were called. If you don't override these, it might be picked up automatically. Do you have time to test this? Otherwise I will have a go, but I'm less familiar with nbphinx.

A

[AA-Turner]

2982b7a restores the key so the extension no longer fails with an exception, but work may be needed in nbsphinx still.

A