`quarto convert` strips div properties off single header book documents

[malcolmbarrett]

Bug description

I'm experimenting with using quarto convert to go to a Jupyter notebook, run ruff, then convert back to a Quarto file. I noticed a couple of quirks with this process. This one seems like a bug.

Steps to reproduce

Example: convert.qmd:

# Preface {.unnumbered}

## Quarto

Quarto enables you to weave together content and executable code into a finished document.
To learn more about Quarto see <https://quarto.org>.

## Running Code

When you click the **Render** button a document will be generated that includes both content and the output of embedded code.
You can embed code like this:

```{python}
1 + 1
```

You can add options to executable code like this

```{python}
#| echo: false
2 * 2
```

The `echo: false` option disables the printing of code (only output is displayed).

When I convert back and forth with

quarto convert convert.qmd
quarto convert convert.ipynb

{.unnumbered} gets eaten in the process

---
title: Preface
jupyter: python3
---


## Quarto

Quarto enables you to weave together content and executable code into a finished document.
To learn more about Quarto see <https://quarto.org>.

## Running Code

When you click the **Render** button a document will be generated that includes both content and the output of embedded code.
You can embed code like this:


```{python}
1 + 1
```

You can add options to executable code like this

```{python}
#| echo: false
2 * 2
```

The `echo: false` option disables the printing of code (only output is displayed).

Actual behavior

No response

Expected behavior

I'm not exactly sure HOW it should happen, but I don't believe {.unnumbered} should disappear.

Your environment

No response

Quarto check output

quarto check
Quarto 1.7.22
[✓] Checking environment information...
      Quarto cache location: /Users/malcolmbarrett/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.85.1: OK
      Deno version 1.46.3: OK
      Typst version 0.13.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.7.22
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: 869685

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/malcolmbarrett/Library/TinyTeX/bin/universal-darwin
      Version: 2023

[✓] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
      Source: MacOS known location

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.12.1
      Path: /Users/malcolmbarrett/.virtualenvs/r-reticulate/bin/python3
      Jupyter: 5.7.2
      Kernels: python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........OK
      Version: 4.4.2
      Path: /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources
      LibPaths:
        - /Users/malcolmbarrett/Library/R/arm64/4.4/library
        - /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library
      knitr: 1.50
      rmarkdown: 2.29

[✓] Checking Knitr engine render......OK

[cscheid]

Thanks for the report. In general, titles in H1 headings are a bit of a fragile area for Quarto, because of the number of places we need to detect them, and how to handle the document structure they imply. It might be safer to use title: as a workaround.

[malcolmbarrett]

How would one keep {.unnumbered} if using title in the YAML instead of in an H1 header?

[cscheid]

How would one keep {.unnumbered} if using title in the YAML instead of in an H1 header?

(I assume that you tried using just that in the title and it didn't work, in which case) We really need to fix sooner rather than later, then.