Refactor chunk hook to handle verbatim-like engine better

[cderv]

WIP: needs #4732 to be merged before this is then merged in main. The current diff is compared the branch in #4732

This is a draft PR and should not be merged yet. Opened for discussion and sharing work.

verbatim and embed knitr's engine should not be exception and their lang option needs to be used correctly.

• refactor handling of block attributes
• create backticks enclosing dynamically according to code content. This is to correctly handle potential block code content using backticks already like fenced.echo in Quarto or verbatim-like engine in knitr to show markdown content.
• Add more comments to remember why and how it works
• exclude some engine from chunk hook .cell-code related processing

Probably require some specific review to decide if this is worth doing in 1.3 or later.

Warning: if we don't want to move knitr min requirement to 1.38, we need to copy create_fence() for its logic into our R code.

[eitsupi]

@cderv Hi, I tried Quarto 1.3 today and noticed that prql code blocks by prqlr is not rendering as expected. (PRQL/prqlc-r#109)
I also noticed that the lang option is ignored.

I am planning a new release of prqlr, do I need to switch here to use the engine option instead of the lang option to change the language of the rendered code blocks?

[cderv]

Thanks for reaching out @eitsupi.

Yes quarto is not perfect for custom engine yet. lang option support is part of this PR on hold.

quarto-cli/src/resources/rmd/hooks.R

Line 393 in 5f88417

lang <- tolower(options$lang %||% knitr:::eng2lang(options$engine))

This is currently missing in 1.3 where we have

quarto-cli/src/resources/rmd/hooks.R

Line 388 in 94a815f

lang <- tolower(options$engine)

This is not the only issue hence this refactoring PR.

We are "freezing" changes for now as we are preparing for 1.3 release - that is why this PR is on hold. However, I'll see with the team if I can cherry-pick this change into main before 1.3 release.

Otherwise, you'll need some workaround in your custom engine yes. Using options$engine will be one for now.

I wonder if there are other issues with custom engine like yours and maybe we need special attributes in knitr so that Quarto can know which is the type of engine and how it should behave.

I'll try your engine and report on your repo.

[eitsupi]

@cderv Thank you for your immediate reply!
I also tried the glue sql engine by the glue package and that one worked fine. (glue sql uses the engine option to convert output to sql)

Another problem I found was that the code annotations did not work for prql code block (Should be related to #4823).

[cderv]

• To check with this PR:
  This

```{r}
#| output: asis
#| echo: false
file <- readLines("assets/why-shiny.shinylive")
cat(paste0(file, collapse = "\n"))
``` 

should be possible to write

```{asis}
#| file: why-shiny.shinylive
``` 

I think it needs special handling in Quarto.