Code blocks with no language specified have `class="NA"` in generated HTML

[wch]

For example:

#' ```
#' r <- reactive({ compute(bigdata()) } %>%
#'   bindCache({ extract_most_recent_time(bigdata()) })
#' ```

https://github.com/rstudio/shiny/blob/6f46b847e2efb74a0cb82edee4d1c60658d8c9e1/R/bind-cache.R#L60-L63

turns into:

\if{html}{\out{<div class="sourceCode NA">}}\preformatted{r <- reactive(\{ compute(bigdata()) \} \%>\%
  bindCache(\{ extract_most_recent_time(bigdata()) \})
}\if{html}{\out{</div>}}

https://github.com/rstudio/shiny/blob/6f46b847e2efb74a0cb82edee4d1c60658d8c9e1/man/bindCache.Rd#L66-L68

(Note that in the linked code above, it was generated with roxygen2 7.1.1 and does not have the sourceCode class, but the NA issue is still present.)

If ```R is used to open the code block, then it (correctly) turns into class="sourceCode R".

Update: Are curly braces (like ```{r, eval=FALSE}) needed for syntax highlighting?

[gaborcsardi]

Would you prefer dropping the NA or using R instead?

[wch]

I'm conflicted -- I think in most cases, people would want R, but there are many cases where you might want to display non-R text (like tabular data), and then how would you do that? I suppose you could use something like txt, but that's very non-obvious to users.

[maelle]

FWIW pkgdown will assume code blocks with no language specified are R blocks. (or maybe it shouldn't, then 🙂 ) r-lib/pkgdown#1724

[hadley]

I think we should drop the class = "NA" and not imply R.

pkgdown can continue guessing that all unmarked code blocks are R because it will try to parse them, and if they're not valid R code they don't get R syntax highlighting.

[hadley]

Ok, this problem was more subtle than I thought. It only appears if the first character in the code is "r":

library(roxygen2)

out <- roc_proc_text(rd_roclet(), "
#' Title
#'
#' ```
#' r <- 1:10
#' ```
#' @md
foo <- function() {}")[[1]]
out$get_section("description")
#> \description{
#> \if{html}{\out{<div class="sourceCode NA">}}\preformatted{r <- 1:10
#> }\if{html}{\out{</div>}}
#> }

^{Created on 2022-07-10 by the reprex package (v2.0.1)}
vs

library(roxygen2)

out <- roc_proc_text(rd_roclet(), "
#' Title
#'
#' ```
#' x <- 1:10
#' ```
#' @md
foo <- function() {}")[[1]]
out$get_section("description")
#> \description{
#> \if{html}{\out{<div class="sourceCode">}}\preformatted{x <- 1:10
#> }\if{html}{\out{</div>}}
#> }

^{Created on 2022-07-10 by the reprex package (v2.0.1)}