[FR] Rethink the way to output PDF from any format.

Pandoc does have a simple way to print PDF (https://pandoc.org/MANUAL.html#creating-a-pdf)

To produce a PDF, specify an output file with a .pdf extension:

--pdf-engine controls the behavior. Default is to look at the output format, a specific method will be used.

• -t latex or none: pdflatex (other options: xelatex, lualatex, tectonic, latexmk)
• -t context: context
• -t html: wkhtmltopdf (other options: prince, weasyprint, pagedjs-cli; see print-css.rocks for a good introduction to PDF generation from HTML/CSS)
• -t ms: pdfroff
• -t typst: typst

Quarto does not really work that way - this currently limit the way to create a PDF, and this is not really consistent across format.

In Quarto we support format: pdf which assumes LaTeX or ConTeXt enine. And format: typst which will produce PDF file by default.

There is special output-ext that can modify PDF render. output-ext: tex when format: pdf renders a .tex file. And output-ext: typ when format: typst render a .typ file. But this variable output-ext is fragile (try setting output-ext to anything it will not error)

When typst was introduced, format: typst has been created but default to render a PDF file. output-ext can be use to get the .typ.

HTML printing to PDF is not really supported in Quarto (https://github.com/quarto-dev/quarto-cli/issues/222).

Using format: latex does not exactly work the same as format: typst as it won't produce PDF.

We should probably rethink all this, and offer more mechanism to create PDF according to method available like Pandoc allows

• Easy and robust way to opt-out PDF for a format that default to it
• Allow printing to PDF from HTML using an external pdf-engine that supports that.
• Consistent way to produce PDF from Quarto render; or another quarto command (e.g quarto print)

Related Issues / Discussions

• https://github.com/quarto-dev/quarto-cli/issues/222
• https://github.com/quarto-dev/quarto-cli/issues/6084
• https://github.com/quarto-dev/quarto-cli/discussions/7018
• https://github.com/quarto-dev/quarto-cli/issues/4677
• Removing Pandoc's extension to --to latex when using format: pdf (https://github.com/quarto-dev/quarto-cli/issues/6613#issuecomment-1693397040, https://github.com/quarto-dev/quarto-cli/issues/7966)
• https://github.com/quarto-dev/quarto-cli/discussions/9483
• https://github.com/quarto-dev/quarto-cli/issues/13314

Start by comparing Quarto's current format: pdf, format: typst, output-ext, and render behavior with Pandoc's PDF options. Read the related issues and discussions linked in the report before proposing a direction. Done would require an agreed, consistent mechanism for PDF generation, including HTML printing and opting out of default PDF output.