Tweak language in warning for bad fenced divs

[cwickham]

In 1.7, missing newlines before code cells produce a warning about :::. This is the correct behavior, code cells should be prefaced by a newline. However, since the warning may be unexpected for documents that didn't previously generate a warning, we might consider tweaking the language to help people find the problem.

Example

Consider the following document:

---
title: "Untitled"
format: html
---

This does it:
```{r}
1 + 1
```

In 1.6, it is rendered without warning. Intermediate markdown:

---
title: "Untitled"
format: html
keep-md: true
---




This does it:


::: {.cell}

```{.r .cell-code}
1 + 1
```

::: {.cell-output .cell-output-stdout}

```
[1] 2
```


:::
:::

In 1.7, the missing newline before the code chunk, propagates to the markdown:

---
title: "Untitled"
format: html
keep-md: true
---

This does it:
::: {.cell}

```{.r .cell-code}
1 + 1
```

::: {.cell-output .cell-output-stdout}

```
[1] 2
```


:::
:::

An results in the warning:

WARNING (/Users/charlottewickham/Documents/posit/quarto-cli/src/resources/filters/./normalize/astpipeline.lua:341) 
The following string was found in the document: :::

This usually indicates a problem with a fenced div in the document. Please check the document for errors.

[cderv]

So I wanted to find why this change between 1.6 and 1.7.

This is the commit 9cb7ccd part of

• Don't add stray spaces in breakQuartoMd #11442

initially to solve

• Too many line breaks around shortcodes #11441

We were indeed adding a lot of newlines, which were hiding the problem: This works ok without warning when using Jupyter engine

---
title: "Untitled"
format: html
keep-md: true
---

This does it:
```{python}
1 + 1
```

and Julia

---
title: "Untitled"
format: html
keep-md: true
engine: julia
---

This does it:
```{julia}
1 + 1
```

So yes if possible, we could try improving the error message but, here this is a problem with knitr engine, that should probably add a newline as done by Jupyter engine: It adds one after each block

quarto-cli/src/core/jupyter/jupyter.ts

Lines 816 to 817 in e14d224

	// newline
	md.push("\n");

It feels bad to know that 1.7 will trigger many warnings in documents because quarto inserts some divs without adding the necessary newlines in knitr so I think this should be fixed.

I mean Pandoc does not require an empty line between Paragraph and a CodeBlock

❯ quarto pandoc -t native -f markdown
This does it 
```r
1+1 
```
^Z
[ Para
    [ Str "This" , Space , Str "does" , Space , Str "it" ]
, CodeBlock ( "" , [ "r" ] , [] ) "1+1"

So, I think the Jupyter engine does the right thing.

I'll make a fix for that for the knitr engine so it behave the same

[cderv]

I'll make a fix for that for the knitr engine so it behave the same

I have made the fix I had in mind:

• knitr, markdown - Add new lines before creating cell output div #12370

This makes engine: knitr add the new lines before output cell div, like engine: jupyter and engine: julia. engine: knitr being the only one to throw the warning, I think this is good to avoid it for 1.7

Though, I understand this could be up for debate so I did not merge.

In 1.7, missing newlines before code cells produce a warning about :::. This is the correct behavior, code cells should be prefaced by a newline.

Personally, I think that until we don't have a good formatter for .qmd document (something like air for R), enforcing rules like this newline by breaking all existing document is a bit much, especially as this is not yet a all-engine rule.

[cderv]

So, I have merged the PR but am leaving this open as it concerns the message improvement.