Usign `lst-label` and `lst-cap` breaks `output-location` for `revealjs` format

[lrossouw]

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

IF you use lst-label and lst-cap in code chinks then output-location for revealjs format stops working. It is ignored.

Steps to reproduce

---
title: "Show Issue"
format: revealjs
---

## This does not show in columns

```{r}
#| echo: true
#| lst-cap: "Plot iris data in a column"
#| lst-label: lst-plot-iris
#| output-location: column

plot(x=iris$Sepal.Length, y=iris$Sepal.Width)
```


## This does not show in next slide

```{r}
#| echo: true
#| lst-cap: "Plot iris data on next slide"
#| lst-label: lst-plot-iris-2
#| output-location: slide

plot(x=iris$Sepal.Length, y=iris$Sepal.Width)
```

## This works

```{r}
#| echo: true
#| output-location: column

plot(x=iris$Sepal.Length, y=iris$Sepal.Width)
```

## And this too

```{r}
#| echo: true
#| output-location: slide

plot(x=iris$Sepal.Length, y=iris$Sepal.Width)
```

Actual behavior

The output-location is ignored.

An warning messages similar to this is printed:

WARNING (/opt/quarto/1.4.550/share/filters/main.lua:14101) output-location is only valid for cells that echo their code

Expected behavior

output-location should not be ignored, or maybe a warning about unsuported combinations. The current warning message is wrong.

Your environment

• IDE: RStudio Pro 2025.05.0 Build 496.pro5
• OS: Ubuntu 22.04

Quarto check output

Quarto 1.4.550
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.11: OK
      Dart Sass version 1.69.5: OK
      Deno version 1.37.2: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.4.550
      Path: /opt/quarto/1.4.550/bin

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

[✓] Checking LaTeX....................OK
      Using: Installation From Path
      Path: /usr/local/texlive/2024/bin/x86_64-linux
      Version: 2024

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

[✓] Checking Python 3 installation....OK
      Version: 3.10.12
      Path: /usr/bin/python3
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with python3 -m pip install jupyter

[✓] Checking R installation...........OK
      Version: 4.4.0
      Path: /opt/R/4.4.0/lib/R
      LibPaths:
        - /home/LRossou/splines_intercepts_wear_off_training/renv/library/linux-ubuntu-jammy/R-4.4/x86_64-pc-linux-gnu
        - /home/LRossou/.cache/R/renv/sandbox/linux-ubuntu-jammy/R-4.4/x86_64-pc-linux-gnu/3df92652
      knitr: 1.51
      rmarkdown: 2.30

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

[mcanouil]

@lrossouw You have to update your version of Quarto. 1.9 is about to be released and you are using 1.3.433. This version has almost 3 years.

[lrossouw]

Sorry ran the check on the wrong version of quarto. It was using 1.4.550 which I guess is still old. Updated the issue with the correct version. I don't control the installation but will ask if they can update it.

[mcanouil]

I can reproduce on latest development version, although your examples with only a plot is not similar as the conflict could be from cross-reference + output-location, once ruled out here is what is happening:

output-location is specifically designed for RevealJS presentations to control where cell output appears relative to the code.
It works by partitioning cells into separate code and output divs.

• quarto-cli/src/resources/filters/quarto-pre/output-location.lua

  Lines 25 to 45 in 7ba701c

  	-- note: assumes that outputLocationCellHasCode has been called
  	local function partitionCell(el, outputClass)
  	-- compute the code div, being sure to bring the annotations
  	-- along with the code
  	local code = { el.content[1] }
  	local outputIndex
  	if isAnnotationCell(el.content[2]) then
  	tappend(code, {el.content[2]})
  	outputIndex = 3
  	else
  	outputIndex = 2
  	end
  	local codeDiv = pandoc.Div(code, el.attr)
  	local outputDiv = pandoc.Div(tslice(el.content, outputIndex, #el.content), el.attr)
  	outputDiv.attr.identifier = ""
  	outputDiv.attr.classes:insert(outputClass)
  	return { codeDiv, outputDiv }
  	end

However, when you use lst- options (like lst-cap for listing captions), the cell is treated as a listing rather than a regular code cell. The filter checks if the cell has a code block using outputLocationCellHasCode(), and if not, it issues the warning "output-location is only valid for cells that echo their code".

• quarto-cli/src/resources/filters/quarto-pre/output-location.lua

  Lines 19 to 23 in 7ba701c

  	local function outputLocationCellHasCode(el)
  	return #el.content > 0 and
  	el.content[1].t == "CodeBlock" and
  	el.content[1].attr.classes:includes("cell-code")
  	end

• quarto-cli/src/resources/filters/quarto-pre/output-location.lua

  Lines 90 to 93 in 7ba701c

  	else
  	warn("output-location is only valid for cells that echo their code")
  	newBlocks:insert(block)
  	end

This design makes sense because output-location needs to physically separate code from output, but listings (lst- options) are meant to display code as a figure/listing without execution output.

AS a workaround, you can use the div syntax, but note that this will make both input/output part of the listing.

::: {#lst-plot-iris}

```{r}
#| echo: true
#| output-location: column
plot(x = iris$Sepal.Length, y = iris$Sepal.Width)
```

Plot iris data in a column

:::

[lrossouw]

Thanks for reproducing. I was about to do it on a system where I control the installation. And thanks for the workaround. I just removed the lst- options as they weren't important for the use case in question. Just took some time to figure out why the output-location wasn't working.

... but listings (lst- options) are meant to display code as a figure/listing without execution output.

I am not sure that I agree with this. I have documents (in other formats) where I have code to produce a figure and the code that produces the figure has a listing. In these other documents the code gets a listing reference and the figures get figure captions and everythign works. I.e. these are examples of lst- and output being used in documents that work.

In fact the documentation has this example which uses lst- options with code that has output.

```{python}
#| label: fig-plot
#| fig-cap: Figure caption
#| lst-label: lst-plot
#| lst-cap: Listing caption

plt.plot([1,23,2,4])
plt.show()
```

The code in @lst-plot produces the figure in @fig-plot.

I think I spotted more bugs in relation to this in revealjs but I will limit to this one. E.g. I think there was a case where a figure caption was not shown where a lst-cap was present.

[lrossouw]

As an additional point the newer quarto (1.6.42 in thsi case) hides the listing too. The output for the first block in my reproducible example does not even have the code block present anymore (despite having echo: true), but shows the listing caption. The image below shows this.

[mcanouil]

... but listings (lst- options) are meant to display code as a figure/listing without execution output.

I am not sure that I agree with this.

That's what the code for Reveal.js suggests. Other formats do not support output-location. The comment was targeted at Reveal.js specifically.
If you take the same example, it works in all formats.

I explained the logic with output-location and the logic with listing. None of your additional examples change that, so in this context it's expected. That does not mean the behaviour should remain like this, don't get me wrong.

And yes there are other issues with listing that you can find: https://github.com/quarto-dev/quarto-cli/issues

@lrossouw

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