Extract `setup` code chunk from `.qmd` file and execute (source) it

I am looking for a way to extract a code block / chunk named setup from a .qmd file and execute the code block (effectively sourcing it, I assume).

Is there a way of achieving this?

I am using rmarkdown::yaml_front_matter()$params to get the parameter, but looking into other functions in the knits package did not help.

Solution

Supposing you have foo.qmd like this:

---
output: revealjs
---

```{r setup}
library(tidyr)
library(stringr)
```

```{r}
iris
```

You can use parsermd to parse the file and extract the item you want (code chunks, headings, etc.). Then, remove the elements from the markdown syntax and evaluate the code:

library(parsermd)
  
rmd <- parse_rmd("foo.qmd")
  
setup_chunk <- rmd_select(rmd, "setup") |> 
  as_document()

setup_chunk <- setup_chunk[-grep("```", setup_chunk)]
setup_chunk
#> [1] "library(tidyr)"   "library(stringr)" ""                

eval(parse(text = setup_chunk))

An alternative is to write setup_chunk to a file and source() it.