Folding occurs on result code blocks that have specific language classes

[atusy]

Currently, application of code folding depends on whether code blocks have specific language classes (r, python, bash, sql, cpp, stan, julia)

https://github.com/rstudio/rmarkdown/blob/d4b7bf18b95371cb57e5f54aff579d70a6651396/inst/rmd/h/navigation-1.1/codefolding.js#L20

Thus, code folding is applied for result code blocks if they have the above classes. This can be an unexpected behavior for users.

---
output:
  html_document:
    code_folding: show
---

```{r, class.output='r', comment=''}
identity
```

xfun::session_info('rmarkdown')

R version 3.6.1 (2019-07-05)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 9 (stretch), RStudio 1.2.1335

Locale:
  LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8     LC_MONETARY=en_US.UTF-8    LC_MESSAGES=C             
  LC_PAPER=en_US.UTF-8       LC_NAME=C                  LC_ADDRESS=C               LC_TELEPHONE=C             LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

Package version:
  base64enc_0.1.3  digest_0.6.20    evaluate_0.14    glue_1.3.1       graphics_3.6.1   grDevices_3.6.1  highr_0.8        htmltools_0.3.6  jsonlite_1.6    
  knitr_1.23       magrittr_1.5     markdown_1.0     methods_3.6.1    mime_0.7         Rcpp_1.0.1       rmarkdown_1.14.1 stats_3.6.1      stringi_1.4.3   
  stringr_1.4.0    tinytex_0.14     tools_3.6.1      utils_3.6.1      xfun_0.8         yaml_2.2.0      

Pandoc version: 2.7.3

---

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[cderv]

This has been now generalized by the PR #1835 but it did not fix this specific issue. folding is still apply also on the output code chunk if it has the language class (or foldable) and if source and results are not collapsed.

The related issue in yihui/knitr#1730 could help solve it to target source or output only.

For now nothing differentiate source code block from output code block

[royfrancis]

So, it possible to fold an arbitrary piece of code block which is not assigned any language?

```
random code
```

Another option would be to assign any language to it, so that it folds, but skip syntax coloring.

sh seems to be an odd one. It is not in the list, but doesn't give an error. It renders fine with syntax coloring, but doesn't fold.

[atusy]

If you want to fold languages not on the list, add foldable class.

```{sh, class.source = "foldable"}
echo foo
```

This is done by https://github.com/rstudio/rmarkdown/pull/1835

[atusy]

BTW, I recommend open a new issue when the topic does not match exactly.

By doing so, you will also see an issue guide that suggests you ask questions on RStudio Community or Stack Overflow.

[cderv]

Thanks @atusy ! Class is foldable though, isn't it ?

Documentation is here: https://bookdown.org/yihui/rmarkdown-cookbook/fold-show.html

[atusy]

Oops, my typo. Thanks @cderv