execution is attempted on document without executable code

[aronatkins]

Bug description

Using Quarto 1.3.340 on macOS.

Given an index.qmd file containing the following content, Quarto attempts to run the embedded R Markdown document.

# Simple Markdown

This is a simple Markdown document containing an embedded R Markdown document.

````markdown
---
title: "making a GET"
---

This shows you how to perform an HTTP connection to some server.

```{r setup, echo = FALSE, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

```{r libraries, echo = FALSE, message = FALSE}
library(httr)
```

```{r fetch, echo = FALSE}
serverURL <- "http://localhost:3939/"

res <- httr::GET(serverURL, httr::write_memory())
if (httr::http_error(res)) {
  err <- sprintf(
    "%s request failed with %s",
    res$request$url,
    httr::http_status(res)$message
  )
  message(capture.output(str(httr::content(res))))
  stop(err)
}
```
````

The resulting error:

quarto preview index.qmd
#> 
#> 
#> processing file: index.qmd
#>   |..................................................        |  86% [fetch]
#> Quitting from lines 21-33 [fetch] (index.qmd)
#> Error in `curl::curl_fetch_memory()`:
#> ! Failed to connect to localhost port 3939 after 1 ms: Couldn't connect to server
#> Backtrace:
#>  1. httr::GET(serverURL, httr::write_memory())
#>  2. httr:::request_perform(req, hu$handle$handle)
#>  4. httr:::request_fetch.write_memory(req$output, req$url, handle)
#>  5. curl::curl_fetch_memory(url, handle = handle)
#> 
#> Execution halted

This document was not meant to be executed.

quarto inspect index.qmd | jq .engines
#> [
#>   "knitr"
#> ]

Checklist

• Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.
• Please provide the output of quarto check so we know which version of quarto and its dependencies you're running.

[aronatkins]

Closely related to #5602.

[aronatkins]

[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.1: OK
      Dart Sass version 1.55.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.3.340
      Path: /Applications/RStudio.app/Contents/Resources/app/quarto/bin

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

[✓] Checking Python 3 installation....OK
      Version: 3.9.6
      Path: /Library/Developer/CommandLineTools/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: 3.6.3
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/3.6/Resources/library
      knitr: 1.42.8
      rmarkdown: 2.20

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

[aronatkins]

Workaround: Add the following YAML to the document:

---
execute:
  eval: false
---

[aronatkins]

The execute>eval trick still requires knitr, which means that R and knitr need to be available to Quarto.

[machow]

Just to add an additional case here. In python it executes and quartos guts are showing.

example.qmd:

---
format: gfm
keep-md: true
jupyter:
  kernelspec:
    display_name: Python 3 (ipykernel)
    language: python
    name: python3
---

# example

```{python}
doc = """
    ```{python}
    1 + 1
    ```
"""
```

example.md:

# example

doc = ““”

    ::: {.cell execution_count=1}
    ``` {.python .cell-code}
    1 + 1
    ```

    ::: {.cell-output .cell-output-display execution_count=6}
    ```
    2
    ```
    :::
    :::

““” \`\`\`

(same result if you change the outermost {python} to python)

[cscheid]

@machow I agree that this is a truly ugly part of our stack. We're not going to have a good solution for you in the short term. I think this is the same behavior on knitr (which is similarly awful wrt this).

I think the recommended workaround is to use double curly brackets there.

This will produce the output you want:

---
format: gfm
keep-md: true
jupyter:
  kernelspec:
    display_name: Python 3 (ipykernel)
    language: python
    name: python3
---

# example

```python
doc = """
    ```{{python}}
    1 + 1
    ```
"""
```

# example

```` python
doc = """
    ```{python}
    1 + 1
    ```
"""
````

(I personally think this is terrible! But the proper fix is super annoying and hard to do right.)