Quarto equivalent to rmarkdown::metadata?

[bastienchassagnol]

Description

Is there an equivalent in Quarto to function rmarkdown::metadata?

If not, what would be the closest way to reproduce this behaviour, when calling quarto interactively, in a R script.

And I'm not considering the meta shortcode, as I do want to retrieve the list of Yaml options from my R script.

Precisely, I want to retrieve the pdf-engine key, as my computation (table outputs) is depending on the latex engine.

[mcanouil]

In LUA, there is "Meta".

In everything else, there is an environment variable that stores a JSON, for example using R:

jsonlite::read_json(
  Sys.getenv("QUARTO_EXECUTE_INFO")
)

[bastienchassagnol]

Thanks, however this does not seem to work (returns an empty string) on my use case, while the old trick of calling rmarkdown::metadata returns exactly what I need (namely the yaml options of my current quarto document, and only that).

# different ways to access quarto metadata ----
## Many things listed in quarto_metadata, like default options, but not the current options used in the yaml
quarto_metadata <- knitr::opts_current$get()
saveRDS(quarto_metadata, "./quarto_metadata.rds")

## Returns an empty string, maybe not using it properly
quarto_metadata_second_way <- Sys.getenv("QUARTO_EXECUTE_INFO") # same output here by wrapping the call with `json`
saveRDS(quarto_metadata_second_way, "./quarto_metadata_second_way.rds")

## This command returns exactly the yaml of the header, great!! :-)
rmarkdown_metadata <- rmarkdown::metadata
saveRDS(rmarkdown_metadata, "./rmarkdown_metadata.rds")

## Returns only the output file
rmarkdown_pandoc_args <- knitr::opts_knit$get("rmarkdown.pandoc.args")
saveRDS(rmarkdown_pandoc_args, "./rmarkdown_pandoc_args.rds")

Full use Case.

Same outcome, whether I'm using:

• The shortcut Ctrl+Shift+K (R Studio preview).
• quarto::quarto_render()

[mcanouil]

It does work.

You need the current stable release.

[bastienchassagnol]

Indeed, since I switched my Quarto version from 1.6 to 1.8, your tip is working. Two additional, complementary questions:

1. I can retrieve the pdf-engine in two ways from variable QUARTO_EXECUTE_INFO (see below). I premised that format$pandoc$pdf-engineretrieves the actually used pdf-engine (accordingly, it has always a value, provided my ouput is a pdf), whileformat$metadata$format$pdf$pdf-engine retrieves the actual value of pdf-engine key in the Yaml of my document (personalised), is that right?

quarto_metadata <- jsonlite::read_json(
  Sys.getenv("QUARTO_EXECUTE_INFO")
)
engine <- quarto_metadata$format$pandoc$`pdf-engine` 
engine <- quarto_metadata$format$metadata$format$pdf$`pdf-engine`

2. Should I consider using rmarkdown::metadata as deprecated for Quarto versions above 1.8? Complementary question: I do think that it's a really cool feature, and that variable QUARTO_EXECUTE_INFO stores lots of relevant informations for enhanced customisation -> di you plan to further document it in the official Quarto?

In any case, thanks for your reactivity.

[mcanouil]

rmarkdown::metadata cannot be deprecated as it was never a Quarto feature.
That's a Rmarkdown/knitr feature which happens to work in Quarto if and only if the engine is knitr.

[cderv]

@bastienchassagnol let me try to answer your question more precisely.

Should I consider using rmarkdown::metadata as deprecated for Quarto versions above 1.8?

rmarkdown::metadata() is still in rmarkdown and it always was a way to get access to metadata from a Rmd document. It does so by passing the parsed frontmatter as metadata.

This worked in Quarto with some limitations as .qmd and .rmd are similar. But all metadata not in the YAML header of a document would not be in the rmarkdown::metadata() results. So it was always limited.

I do think that it's a really cool feature, and that variable QUARTO_EXECUTE_INFO stores lots of relevant informations for enhanced customisation

It does, and this is why we've done it. However, this is shiny new. late addition in 1.8 as pre-release, and now available in last release 1.8.24 that we released just this end of week. And we did not even yet done a release blog post or announcement and this will come later.

So really new, and indeed you couldn't have known. Mickael have been able to answer you as he is aware of every latest development, sometimes before release. So his answer sometimes assumes all users follow and do use latest stable version as they are out ! 😄 😉

do you plan to further document it in the official Quarto?

We do plan to document it as it goes, and we do plan to add some wrapper access function in quarto R package.

• Provides helpers to access information about the execution environment quarto-r#285

Maybe we will also make rmarkdown::metadata() return all quarto_metadata$format$metadata in Quarto context. Could be a nice feature request.

Anyhow, I hope this clarifies. Before 1.8, you could not retrieve pdf-engine if it was not set in YAML header of the document.

I premised that format$pandoc$pdf-engineretrieves the actually used pdf-engine (accordingly, it has always a value, provided my ouput is a pdf), whileformat$metadata$format$pdf$pdf-engine retrieves the actual value of pdf-engine key in the Yaml of my document (personalised), is that right?

Yes something like that. We are exposing the whole internal execute information. So it needs some polishing on the user side to use the correct one. I acknowledge this is not straighforward, and indeed considered advanced usage right now. But you'll find what you need !!

And please report anything that looks odd, or open idea on https://github.com/quarto-dev/quarto-r for function that would have help you retrieve the useful information.

Hope it helps clarify a bit the context, and your question was perfectly timed with 1.8 release :)

[bastienchassagnol]

Many thanks for your detailed and comprehensive answer, @cderv — it really helped clarify the remaining points.