accessing headers in chapters via lua filter

[eeholmes]

Description

Quarto version 1.5.55

I am writing a lua filter to edit chapter headers in a Quarto book. However my filter doesn't access the level 1 headers in chapters, only in the index.qmd. I can see the problem in the page source but I don't know how to solve it.

_quarto.yml

project:
  type: book
book:
  title: "test"
  chapters:
    - index.qmd
    - one.qmd
filters:
  - test.lua

test.lua

function Header(el)
  quarto.log.output(pandoc.utils.stringify(el.level))
end

index.qmd and one.qmd

# One

## Two

### Three

What I see in the pandoc output. The numbers are the level of the headers encountered. My filter is not "seeing" the level 1 header in the first chapter (one.qmd).

[1/2] index.qmd
1
2
3
[2/2] one.qmd
2
3

What I expect to see. Both qmd are identical with the same three headers.

[1/2] index.qmd
1
2
3
[2/2] one.qmd
1
2
3

Looking at the page source, I see the problem I think. The <h1> with the chapter title is inside a <header> block. But I don't know how to change my filter to get "inside" the header block. I don't actually care about the h1 headers. I am trying to change the <span class="chapter-number"> that is in <header> but I don't know how to access it.

Here is the page source from one.html

<header id="title-block-header" class="quarto-title-block default">
<div class="quarto-title">
<h1 class="title"><span class="chapter-number">2</span>&nbsp; <span class="chapter-title">One</span></h1>
</div>
<div class="quarto-title-meta">
 </div>
</header>
<section id="two" class="level2" data-number="2.1">
<h2 data-number="2.1" class="anchored" data-anchor-id="two"><span class="header-section-number">2.1</span> Two</h2>
<section id="three" class="level3" data-number="2.1.1">
<h3 data-number="2.1.1" class="anchored" data-anchor-id="three"><span class="header-section-number">2.1.1</span> Three</h3>

Here is the page source from index.html

<header id="title-block-header" class="quarto-title-block default">
<div class="quarto-title">
<h1 class="title">test</h1>
</div>
<div class="quarto-title-meta"> </div>
</header>
<section id="one" class="level1" data-number="1">
<h1 data-number="1"><span class="header-section-number">1</span> One</h1>
<section id="two" class="level2" data-number="1.1">
<h2 data-number="1.1" class="anchored" data-anchor-id="two"><span class="header-section-number">1.1</span> Two</h2>
<section id="three" class="level3" data-number="1.1.1">
<h3 data-number="1.1.1" class="anchored" data-anchor-id="three"><span class="header-section-number">1.1.1</span> Three</h3>

[mcanouil]

• How to get chapter title in book project #8999

[eeholmes]

Here is my minimal repo for what I am doing. It very nearly works https://github.com/nmfs-opensci/chapnum-equations

[eeholmes]

Ok, I think I might know what's going on. I think this is a pandoc.MetaBlock and I need to tell the filter to work on that. Right now it is working blocks and pandoc treats titles differently, as MetaBlocks even when in a Quarto book.

[mcanouil]

Just in case, are you using format: native? This format will output the AST.

[eeholmes]

I tried using format: native but it said it is not available for project type book. Sadly.

[ute]

@eeholmes , have you found out how to get the chapter number in an easy way?
I needed this for custom-numbered-blocks, and it was quite epic at that stage (still quarto 1.3 then). Information about chapters is contained in meta.book.render. You need to know the filename to identify the chapter number.