Function for printing color formatted Stan code in Quarto

[avehtari]

How about adding a helper function to make it easier to have color formatted Stan code in Quarto files?

I've been recently been using something like the following

print_stan_file <- function(file, fold = FALSE, summary = "Stan model code") {
  code <- readLines(file)
  if (isTRUE(getOption("knitr.in.progress")) &
        identical(knitr::opts_current$get("results"), "asis")) {
    if (fold) {
      cat("<details><summary>", summary, "</summary>\n\n", sep = "")
    }
    cat("```stan\n")
    cat(code, sep = "\n")
    cat("\n```\n")
    if (fold) {
      cat("\n</details>\n")
    }
  } else {
    writeLines(code)
  }
}

Which is used in Quarto as

#| output: asis
print_stan_file(stan_model_file_path)

If the function is called outside of rendering or without output: asis, it will write the plain code. If the function is called when rendering and Quarto block option output: asis is used, the output will be color formatted.

Additional argument fold makes the code to be folded with title provided by argument summary

[jgabry]

We have a print method for CmdStanModel objects (model$print()) that prints the Stan code. What about updating that method to optionally handle this too instead of introducing an additional new function?

[avehtari]

model$print() requires first compiling a complete model and separate function could be used to print also parts of code that is actually never compiled alone, e.g., blocks that are included with #include

model$print() could get the same functionality, but there would be benefits of being able to call such function separately

[jgabry]

Oops, I accidentally edited your comment when I meant to quote it in my response! Working on too many things at one! I'll edit it back to your original comment.

[jgabry]

Oops, I accidentally edited your comment when I meant to quote it in my response! Working on too many things at one!

Fixed. I reverted my edits to your comment. I'll add my responses below.

model$print() requires first compiling a complete model

You can set compile = FALSE in cmdstan_model(), but yeah it does at least require creating a model object, regardless of whether or not you do compilation.

separate function could be used to print also parts of code that is actually never compiled alone, e.g., blocks that are included with #include

Yeah that could be useful

there would be benefits of being able to call such function separately

Ok yeah then I think a good place to put this new function would be with write_stan_file(). Right now write_stan_file() is defined in example.R with the example models, but we could move that to its own file and add the print_stan_file() function there too. Once we have the new function we can decide whether or not to add the same functionality to model$print() (maybe it's best to leave it the way it is).