KeyError: 'classes' in sphinx.search

[ElpadoCan]

Describe the bug

When building the html files locally with make.bat html I get the error below. This does not happen with Sphinx<8.2. I can see that it comes from sphinx\search\__init__.py which did not exist prior v8 of Sphinx right? I hope this is enough information. Thanks!

Traceback (most recent call last):
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\cmd\build.py", line 432, in build_main
    app.build(args.force_all, args.filenames)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\application.py", line 426, in build
    self.builder.build_update()
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\__init__.py", line 375, in build_update
    self.build(
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\__init__.py", line 454, in build
    self.write(docnames, updated_docnames, method)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\__init__.py", line 735, in write
    self.write_documents(docnames)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\__init__.py", line 749, in write_documents
    self._write_serial(sorted_docnames)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\__init__.py", line 767, in _write_serial
    self.write_doc_serialized(docname, doctree)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\html\__init__.py", line 684, in write_doc_serialized
    self.index_page(docname, doctree, title)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\builders\html\__init__.py", line 1021, in index_page
    self.indexer.feed(pagename, filename, title, doctree)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\search\__init__.py", line 503, in feed
    word_store = self._word_collector(doctree)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\search\__init__.py", line 554, in _word_collector
    _feed_visit_nodes(
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\search\__init__.py", line 643, in _feed_visit_nodes
    _feed_visit_nodes(child, word_store=word_store, split=split, language=language)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\search\__init__.py", line 643, in _feed_visit_nodes
    _feed_visit_nodes(child, word_store=word_store, split=split, language=language)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\search\__init__.py", line 643, in _feed_visit_nodes
    _feed_visit_nodes(child, word_store=word_store, split=split, language=language)
  File "%homepath%\miniforge3\Lib\site-packages\sphinx\search\__init__.py", line 608, in _feed_visit_nodes
    elif isinstance(node, nodes.Element) and 'no-search' in node['classes']:
                                                            ~~~~^^^^^^^^^^^
  File "%homepath%\miniforge3\Lib\site-packages\docutils\nodes.py", line 602, in __getitem__
    return self.attributes[key]
            ~~~~~~~~~~~~~~~^^^^^
KeyError: 'classes'

How to Reproduce

Unfortunately, I don't know which of my documentation files is triggering this error (and I have many), however, the error does not happen with Sphinx<8.2.

Environment Information

Platform:              win32; (Windows-10-10.0.19045-SP0)
Python version:        3.12.6 | packaged by conda-forge | (main, Sep 22 2024, 14:01:26) [MSC v.1941 64 bit (AMD64)])
Python implementation: CPython
Sphinx version:        7.4.7
Docutils version:      0.21.2
Jinja2 version:        3.1.6
Pygments version:      2.19.1

Sphinx extensions

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

* sphinx.ext.mathjax (8.2.3)
* alabaster (0.7.16)
* 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)
* sphinx.ext.duration (8.2.3)
* sphinx.ext.doctest (8.2.3)
* sphinx.ext.autodoc.preserve_defaults (8.2.3)
* sphinx.ext.autodoc.type_comment (8.2.3)
* sphinx.ext.autodoc.typehints (8.2.3)
* sphinx.ext.autodoc (8.2.3)
* sphinx.ext.autosummary (8.2.3)
* sphinx.ext.napoleon (8.2.3)
* sphinx_copybutton (0.5.2)
* sphinxcontrib.email (0.3.6)
* sphinx_tabs.tabs (unknown version)
* sphinx_toolbox.confval (3.9.0)
* sphinx_carousel.carousel (1.2.0)
* sphinxcontrib.video (unknown version)
* sphinxcontrib.jquery (4.1)
* sphinx_rtd_theme (unknown version)

Additional context

No response

[AA-Turner]

Are you able to provide a minimal reproducer? If not, can you please try with third-party extensions removed?

A

[ElpadoCan]

Are you able to provide a minimal reproducer? If not, can you please try with third-party extensions removed?

A

I will try. Is there any way to know more than the traceback? For example, what causes the creation of the node dictionary without classes? Because I used pdb.set_trace and many of the nodes are fine.

[ElpadoCan]

Ok, so the problem is the extension sphinx_carousel. Unfortunately, this extension has been archived, but since it is pretty convenient is there anything that can be done on Sphinx's side to make it work?

I attached a folder with a minimal example. Let me know thanks!

sphinx_gh_issue_minimal_example.zip

[AA-Turner]

Does https://sphinx-design.readthedocs.io/en/latest/cards.html#card-carousels work as a replacement for sphinx-carousel?

[ElpadoCan]

Does https://sphinx-design.readthedocs.io/en/latest/cards.html#card-carousels work as a replacement for sphinx-carousel?

That is an interesting idea, but the sphinx-carousel looks nicer because it is like a slideshow for images that are timed and go through the slideshow like a GIF. I guess a GIF would also do the trick?

[AA-Turner]

Unfortunately, this extension has been archived, but since it is pretty convenient is there anything that can be done on Sphinx's side to make it work?

I've looked in to this. The problem is that sphinx-carousel overwrites a core internal attributes Element.attributes, which means that even if I added workaround code in this instance, there are no guarantees that it will keep working in the future. I am surprised it stayed working for so long, actually!

If the original author is willing to do so, we can move the extension to @sphinx-doc or @sphinx-contrib. If you have sucess in emailing them, please let me know. Otherwise, I think the best option is to find a replacement extension (or fork it and maintain yourself).

Sorry that this isn't better news, but I don't think there is much room for manoeuvre.

Thanks,
Adam