Provide a syntax definition file with updated support for R new syntax

[cderv]

First issue has been reported in rstudio/bookdown#1157. See discussion there for details. In a nutshell:

• Pandoc's highlighting uses KDE XML syntax file
• the KDE XML syntax file for R language does not correctly handles the new R syntax.

Current fix in rmarkdown is for html_document_base() only as a post processing - see 99df4e7 . This fixes the issue rstudio/bookdown#1157

Proper fix should be:

• Push upstream correct support for Pandoc for later Pandoc's version.
• Use the XML definition file directly in rmarkdown for previous pandoc version that won't have the updated support, using --syntax-definition flag.

[cderv]

From a report in tidyverse/reprex#389, let's acknowledge that the current fix is not working for github_document() HTML preview

---
title: "Minimal Example"
output: 
  github_document: default
  html_document:
    highlight: pygments
---

```{r}
library(magrittr)
1.23 %>% round()
1.23 |> round()
```

[cderv]

Waiting for this to be completely fixed, I published a gist with a patched xml file one could use: https://gist.github.com/cderv/079b78caefbe45da6d1c03d737970b55

It can be downloaded then used by adding pandoc_args in YAML header. e.g with pdf_document()

output: 
  pdf_document:
    pandoc_args: "--syntax-definition=r.xml"

See comment here for more detail and example on how to set a font for having the ligature in PDF

rstudio/bookdown#1157 (comment)

[yihui]

Could you submit a PR to KDE? I guess this is the file to edit: https://invent.kde.org/frameworks/syntax-highlighting/-/blob/master/data/syntax/r.xml The earlier we submit a PR, the better, since it will take time for the upstream change (if merged) to propagate to Pandoc.

[cderv]

I wanted to try add support for new syntax to define function too

(\(x) x + 1)(2)
#> [1] 3

But I still haven't done the KDE file update for this.

You're right I should do it wit the current addition.

[cderv]

PR opened in KDE repo: https://invent.kde.org/frameworks/syntax-highlighting/-/merge_requests/295

[cderv]

PR has been merged - they dealt with the KDE specific compilation. This means that next Pandoc version should have the new file included as they pull from the KDE repo in https://github.com/jgm/skylighting to be included in Pandoc.

[yihui]

It seems skylighting has picked up the changes: jgm/skylighting@8bb0095#diff-250158d7bb3fc1cdf086670cbd7ea7fe8ccb68f6004b3739b36960d574372e35

I guess we should also submit a PR to KDE with 5514393, right?

[cderv]

Yes it has picked up the change and also Pandoc (jgm/pandoc@2a70d9c) but not yet in a release. Next one should have it.

I have still a PR in skylighting for markdown.xml from Quarto but not sure it will be merged.

PR for KDE with last change is ready but not yet online. I have prepare that yesterday with the changes in the PR.

[yihui]

Yes it has picked up the change and also Pandoc (jgm/pandoc@2a70d9c) but not yet in a release. Next one should have it.

It seems to be shipped in Pandoc 2.18. The RStudio IDE uses Pandoc 3.x now, so perhaps we can drop r.xml in the #2290? (which means we just don't support syntax highlighting the pipe operators for Pandoc < 2.18 users)

[cderv]

Yes it seems ok to do that.