SAS code cells do not render correctly

[michaelwalshe]

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Bug Reports guide

Bug description

SAS code cells do not render as code, despite being supported with comment chars for e.g. eval options and being a knitr execution engine

Steps to reproduce

---
title: "Test SAS Code Cells"
engine: "knitr"
format: html
---

SAS as execution engine, properly parses comment chars but does not display as a code cell.

```{sas}
*| eval: false;
data _null_;
    putlog "Hello from SAS";
run;
```

SAS as CSS class.

```{.sas}
data _null_;
    putlog "Hello from SAS";
run;
```

SAS as markdown.

```sas
data _null_;
    putlog "Hello from SAS";
run;
```

Example with e.g. stata for what should happen.

```stata
display "Hello from Stata"
```

Actual behavior

The above renders to HTML as:

Expected behavior

Should instead render like (produced by setting all to default):

Your environment

• IDE: Positron 2026.03.0
• OS: Windows 11, also tested on WSL Ubuntu 24.04

Quarto check output

> quarto check
Quarto 1.8.27
[>] Checking environment information...
      Quarto cache location: C:\Users\Michael.Walshe\AppData\Local\quarto
[>] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.3.1: OK
      Typst version 0.13.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.8.27
      Path: C:\Program Files\Quarto\bin
      CodePage: 1252

[>] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: (not installed)

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\Users\Michael.Walshe\AppData\Roaming\TinyTeX\bin\windows\
      Version: 2024

[>] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: C:\Program Files\Google\Chrome\Application\chrome.exe
      Source: Windows Registry

[>] Checking basic markdown render....OK

[>] Checking Python 3 installation....OK
      Version: 3.14.0
      Path: C:/Users/Michael.Walshe/AppData/Roaming/uv/python/cpython-3.14.0rc2-windows-x86_64-none/python.exe
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with py -m pip install jupyter

[>] Checking R installation...........OK
      Version: 4.5.2
      Path: C:/PROGRA~1/R/R-45~1.2
      LibPaths:
        - C:/Users/Michael.Walshe/source/personal/scratch/renv/library/windows/R-4.5/x86_64-w64-mingw32
        - C:/Users/Michael.Walshe/AppData/Local/R/cache/R/renv/sandbox/windows/R-4.5/x86_64-w64-mingw32/ebc25411
      knitr: 1.51
      rmarkdown: 2.30

[>] Checking Knitr engine render......OK

[mcanouil]

It can only have syntax-highlighting if the upstream Skylighting library knows "sas".

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[michaelwalshe]

Hi - thanks for the quick reply! I'm not expecting syntax highlighting, I'm expecting the code block to render with a background, copy button, etc similarly as if I'd used the default style:

These should display the same in HTML output, no syntax highlighting but be recognised as a code block. The options are correctly parsed and not rendered for the `{sas}` block when using the knitr engine, but it displays as plain text with no background.

```default
data _null_;
    putlog "Test";
```

```{sas}
*| eval: false;
data _null_;
    putlog "Test";
```

[mcanouil]

Again, if skylighting does not know about the language, that's how the code block is formatted.

quarto pandoc --list-highlight-languages

See:

• https://github.com/jgm/skylighting

Use a clearly unknown language, which "default" is not.

```whateverlanguage
data _null_;
    putlog "Test";
```

You can also set syntax-highlighting: none (new/current name of highlight-style) to see that the background and everything comes from syntax highlighting.

[cderv]

There is several interesting things here:

First, this is true that pandoc does not support highlighting SAS cell with its higlighter. I see no issue about adding to https://github.com/jgm/skylighting. This is probably because KDE itself does not have one: https://github.com/KDE/syntax-highlighting/tree/master/data/syntax

However, those files can be created, and if you search the web you can find some contributions. For example in https://github.com/mcaceresb/highlight-sas-stata there is one. It is old but it is a start: https://github.com/mcaceresb/highlight-sas-stata/blob/master/skylighting/sas.xml
Maybe there are others. You could even try to write one yourself following KDE syntax reference.

Anyhow to use this one I found, download the file

xfun::download_file("https://raw.githubusercontent.com/mcaceresb/highlight-sas-stata/refs/heads/master/skylighting/sas.xml")

then set it in config

---
title: "SAS highlight"
format: html
syntax-definitions: 
  - sas.xml
---

SAS as markdown.

```sas
data _null_;
    putlog "Hello from SAS";
run;
```

Then, regarding your idea of setting default for unknown language, I like this idea. Though this would be good highlighting I think for everything, and pandoc does not fallback. So to have it you need yourself to use

```default
data _null_;
    putlog "Hello from SAS";
run;
```
or 
```{.default}
data _null_;
    putlog "Hello from SAS";
run;
```

However, we know in Quarto we have a theming problem in the sense that you get no code background at all when not using pandoc's highlighting. This is among other styling improvement (for inline for example).

We'll see in future version how we could change that, so this no background code block is no more the default

But this can break style for others, so this is never easy decision.

Hope it helps understand, and give you hints on what to search for and how to tweak for your case.

[michaelwalshe]

Thanks so much for the info & pointers - I knew highlighing was provided upstream from KDE via skylighting, but did not realise that this also powered which languages were treated as code blocks. I'll use that sas.xml in the meantime and will try to update it to get a MR into kSyntaxHighlighting.

In the meantime would agree that updating so unknown languages (or even languages without syntax highlighting support but that do have comment character support like SAS) get default styling would be a good enhancement.