Conflict between sphinx.ext.autosectionlabel and nbsphinx about nbsphinx

[mgeier]

Thanks for the report and for the MWE which makes this easily reproducible!

Only the combination of the three then causes this bug / WARNING.

Are you sure you need all three to cause the problem?
When I remove 'nbsphinx' from the extensions, I still get the warning.

It looks like there is already an issue at sphinx-argparse which doesn't involve nbsphinx: sphinx-doc/sphinx-argparse#14

nbsphinx and autosectionlabel both try to create/embed ids for headings

nbsphinx indeed creates section IDs (because Jupyter uses a different scheme than Sphinx):

nbsphinx/src/nbsphinx/__init__.py

Lines 1275 to 1299 in 311c53b

	class CreateNotebookSectionAnchors(docutils.transforms.Transform):
	"""Create section anchors for Jupyter notebooks.
	Note: Sphinx lower-cases the HTML section IDs, Jupyter doesn't.
	This transform creates anchors in the Jupyter style.
	"""
	default_priority = 200 # Before CreateSectionLabels (250)
	def apply(self):
	all_ids = set()
	for section in self.document.traverse(docutils.nodes.section):
	title = section[0].astext()
	link_id = title.replace(' ', '-').replace('"', '%22')
	if link_id in all_ids:
	# Avoid duplicated anchors on the same page
	continue
	all_ids.add(link_id)
	section['ids'] = [link_id]
	if not all_ids:
	logger.warning(
	'Each notebook should have at least one section title',
	location=self.document[0],
	type='nbsphinx', subtype='notebooktitle')

However, this is only done for *.ipynb source files, and not for "normal" *.rst files:

nbsphinx/src/nbsphinx/__init__.py

Line 534 in 311c53b

CreateNotebookSectionAnchors,

So if I'm not mistaken, this isn't even active in your MWE.

It might lead to problems if a Jupyter notebook is involved, though?

[dkuegler]

I have done some further investigation and I know believe this is not an nbsphinx issue, but argparse. It was a bit hard to trace this issue, as it was thrown in auto section label and I subsequently searched for where labels where also created.