Extension Basics
Extending Quarto workshop @ posit::conf(2025)
What happens when you render?
Inside the Pandoc step
.md → Reader → AST
example.md
## Introduction
In @sec-data
## Data {#sec-data}
Markdown is parsed into a representation called the Abstract Syntax Tree (AST)
AST → Filters → AST
Filters transform nodes in the AST
E.g. cross-references (Quarto), citations (Pandoc), and custom filters (extensions & you).
AST → Writer → .html
<section id="introduction" class="level2">
<h2 class="anchored" data-anchor-id="introduction">Introduction</h2>
<p>In <a href="#sec-data" class="quarto-xref">Section 2</a></p>
</section>
<section id="sec-data" class="level2">
<h2 class="anchored" data-anchor-id="sec-data">Data</h2>
</section>Writers convert the content to the desired output format.
AST → Writer → .html
Combined with boilerplate from template and partials.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head>
...<section id="introduction" class="level2">
<h2 class="anchored" data-anchor-id="introduction">Introduction</h2>
<p>In <a href="#sec-data" class="quarto-xref">Section 2</a></p>
</section>
<section id="sec-data" class="level2">
<h2 class="anchored" data-anchor-id="sec-data">Data</h2>
</section>...
</html>A case study: Course notes
Notes that we want as slides (format: revealjs) and a document (format: html).
Title slide in every slide deck controlled by metadata
Partial
Special slide combines boilerplate with content.
Filter