!expr invalide with message in chunk option

[LBeaulaton]

Bug description

!expr in chunk option don't work for message while it works e.g. error.

Steps to reproduce

---
title: test knitr
# validate-yaml: false
---

```{r}
#| label: chunk1

show.message <- FALSE
```

```{r}
#| label: chunk2
#| error: !expr "show.message"

message("this works")
```

```{r}
#| label: chunk3
#| message: !expr "show.message"

message("this doesn't work")
```

Expected behavior

This should not produce an error message.
Note that with validate-yaml: false not commented I'm able to render the quarto file

Actual behavior

Produce the following error message:

ERROR: Validation of YAML cell metadata failed.
In file test.qmd
(line 21, columns 13--33) Field "message" has value !expr "show.message", which must instead be one of: `true`, `false`, `NA`

Your environment

Ubuntu 24.04
Quarto 16.04
VSCodium 1.92.2

Quarto check output

quarto check
Quarto 1.6.40
[✓] Checking environment information...
      Quarto cache location: /home/lbeaulaton/.cache/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.6.40
      Path: /opt/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (not installed)
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: Installation From Path
      Path: /usr/bin
      Version: 2023

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

[✓] Checking Python 3 installation....OK
      Version: 3.12.3
      Path: /usr/bin/python3
      Jupyter: 5.3.2
      Kernels: python3

(\) Checking Jupyter engine render....Traceback (most recent call last):
  File "/opt/quarto/share/jupyter/jupyter.py", line 21, in <module>
    from notebook import notebook_execute, RestartKernel
  File "/opt/quarto/share/jupyter/notebook.py", line 20, in <module>
    from nbclient import NotebookClient
ModuleNotFoundError: No module named 'nbclient'
[✓] Checking Jupyter engine render....OK

[cderv]

Thanks for opening the issue. !expr is tricky as this is only a knitr engine feature kept for backward compatibility.

First, I can't reproduce any rendering error. And there should not be, because the YAML field inside knitr cells are directly processed by knitr AFAIK. So this renders for me

---
title: test knitr
---

```{r}
#| label: chunk1

show.message <- FALSE
```

```{r}
#| label: chunk2
#| error: !expr "show.message"

message("this works")
```

```{r}
#| label: chunk3
#| message: !expr "show.message"

message("this doesn't work")
```

However, I get the validation linting error in RStudio IDE

And IMO this is because we added autocompletion for true, false, NA which are the fields supported - !expr being an edge case we don't validate againt.

I need to see how our validation system can correctly support official values for fields, while also supporting !expr if possible for knitr engine.

[cderv]

@cscheid I added some specific to message field for knitr at

• New knitr will support #| message: NA to suppress messages in the output and show in console #11312

I believe this now prevents the validation to accept a string and does the !expr specific exception

How can I tell the schema that these are the accepted values

quarto-cli/src/resources/schema/cell-textoutput.yml

Lines 72 to 76 in e4a8898

	- name: message
	tags:
	engine: knitr
	schema:
	enum: [true, false, NA]

and offers to auto complete them.

but also accept string so that !expr syntax does pass in knitr cells ?

I know this is not Quarto feature, but it would be good if we good have a way to accept !expr field in our validation. I don't know how to express this in our YAML schema.