Sphinx 7.2: unknown node type: only

[JasperCraeghs]

Describe the bug

The use of an only-directive that is nested inside of a parent only-directive to conditionally include a directive of the Sphinx plugin breathe fails since Sphinx 7.2. Sphinx<=7.1.2 supports this use case.

/home/user/git/minimal-doc/<partial node>:: WARNING: unknown node type: <only: <list_item...><list_item...><list_item...>>

Traceback (most recent call last):
...
  File "/home/user/git/minimal-doc/venv/lib/python3.10/site-packages/sphinx/util/docutils.py", line 743, in dispatch_departure
    super().dispatch_departure(node)
  File "/home/user/git/minimal-doc/venv/lib/python3.10/site-packages/docutils/nodes.py", line 2005, in dispatch_departure
    return method(node)
  File "/home/user/git/minimal-doc/venv/lib/python3.10/site-packages/docutils/nodes.py", line 2027, in unknown_departure
    raise NotImplementedError(
NotImplementedError: <class 'sphinx.writers.html5.HTML5Translator'> departing unknown node type: only

Exception occurred:
  File "/home/user/git/minimal-doc/venv/lib/python3.10/site-packages/docutils/nodes.py", line 2027, in unknown_departure
    raise NotImplementedError(
NotImplementedError: <class 'sphinx.writers.html5.HTML5Translator'> departing unknown node type: only

How to Reproduce

My minimal git repository contains build output of doxygen, needed for the breathe directive (doxygenfile) to function, which is required to reproduce the bug.

git clone [email protected]:JasperCraeghs/minimal-doc.git
pip install virtualenv
virtualenv venv
source venv/bin/activate
pip install -r requirements.txt
make html

My index.rst:

minimal-doc documentation
=========================

.. only:: html

    hello world

    .. only:: not text

        .. doxygenfile:: component.c

Environment Information

Platform:              linux; (Linux-6.8.0-45-generic-x86_64-with-glibc2.35)
Python version:        3.10.12 (main, Sep 11 2024, 15:47:36) [GCC 11.4.0])
Python implementation: CPython
Sphinx version:        8.1.3
Docutils version:      0.21.2
Jinja2 version:        3.1.2
Pygments version:      2.18.0

Sphinx extensions

["breathe"]

Additional context

The following made me realize that this is likely a bug in sphinx and not in breathe: #10502

I can use directives of other Sphinx plugins in a nested only-directive. The crash is specific to the directives of the breathe plugin. The version of docutils doesn't seem to matter.