Chunk options in bash visible under jupyter engine

[dmi3kno]

Description

When using Jupyter as engine, the chunk options in the bash chunk are rendered visible

---
title: "Untitled"
format: html
engine: python
---

Install using pip

```{bash}
#| eval: false

pip install uv
```

Switching the engine to knitr makes the chunk options disappear (and syntax highlighting enabled)

What am I doing wrong?

[cscheid]

You're doing nothing wrong. Our output is not currently equivalent across engines, and that's something we need to fix. We have an issue open for a slightly different situation, but this is quite related.

[cscheid]

Good point. I still understand the confusion, though. Maybe we should instead be warning users about the situation when {...} cells are not executed?

[mcanouil]

Does Jupyter kernels allow to know that a code cell cannot be executed because the language is unknown to the kernel?

[cscheid]

I believe so, yes - the way Jupyter execution works is that we only send code cells to the kernel if the kernel claims that it's one of the languages it executes. Then Pandoc sees a code block with class {bash} and doesn't know what to do with it, so it's simply written out as is.

[mcanouil]

In that case, I believe Quarto could raise a warning and convert {language} into language (to improve output display), but I don't think that code cell options of an invalid code cell should be evaluated/trimmed anyway.

I don't know if knitr does the same bare code block for "unknown" languages.

[mcanouil]

The behaviour is consistent across engines Jupyter/Julia, but differs for knitr which raises a warning and trims the code cells options.

---
title: "Quarto Playground"
format: html
---

```{fake}
#| eval: false
whatever command you want to run
```

Warning message:
In get_engine(options$engine) :
  Unknown language engine 'fake' (must be registered via knit_engines$set()).

Input	Output
quarto render index.qmd --metadata "engine:knitr"	Warning message: In get_engine(options$engine) : Unknown language engine 'fake' (must be registered via knit_engines$set()).
quarto render index.qmd --metadata "engine:jupyter"
quarto render index.qmd --metadata "engine:julia"

Should we convert this into an enhancement New feature or request issue?