New --number-sections behavior from 3.1.12 creates gap in numbering when .unnumbered class is used

[cderv]

I opening this as a discussion as I am not sure from reading release note, and associated issue of commit of this is expected change or not.

I understand Pandoc 3.1.12 is changing the behavior of MakeSections (03bb426) but not sure how it is supposed to impact section with .unnumbered. They are correctly not numbered, but they now increment the counter.

# pandoc 3.1.12
> pandoc --number-sections -t html
# One {-}

# Two

# Three {-}

# Four
^Z
<h1 class="unnumbered" id="one">One</h1>
<h1 data-number="2" id="two"><span
class="header-section-number">2</span> Two</h1>
<h1 class="unnumbered" id="three">Three</h1>
<h1 data-number="4" id="four"><span
class="header-section-number">4</span> Four</h1>

Previous behavior with 3.1.11.1 : Header with unnumbered class did not increment the section number and were skipped

# pandoc 3.1.11.1
> pandoc --number-sections -t html
# One {-}

# Two

# Three {-}

# Four
^Z
<h1 class="unnumbered" id="one">One</h1>
<h1 data-number="1" id="two"><span
class="header-section-number">1</span> Two</h1>
<h1 class="unnumbered" id="three">Three</h1>
<h1 data-number="2" id="four"><span
class="header-section-number">2</span> Four</h1>

This is quite a breaking change, and I though that .unnumbered class could really be used to have some sections ignored in the numbering - we used this in some project (i.e bookdown in R Markdown ecosystem) to have Part section in HTML that where not meant to be incrementing the chapter numbers.

This is still happening with nightly pandoc, and I found no report yet, so I want to confirm is this is really expected new behavior and we need to adapt, or if this could be unintended side effect of new 3.1.12 behavior.

Thank you.

[jgm]

They shouldn't increment the counter, so it's a bug indeed. Please submit an issue.

[cderv]

Submitted as

• New --number-sections behavior from 3.1.12 increments counter in numbering even when .unnumbered class is used #9516