This is another silly problem, but I'm sure I'm not the only one who has/will run into it! If you mess up your Quarto options and use = instead of : in the code chunk, you will get a pretty impenetrable (to me) error about YAML. For example:
---
title: "Untitled"
format: pdf
editor: visual
---
```{r}
#| label: math
#| echo = false
2 * 2
```
Gives the error
processing file: test.qmd
Error in yaml::yaml.load(meta, handlers = list(expr = parse_only)) :
Scanner error: while scanning a simple key at line 2, column 1 could not find expected ':' at line 3, column 1
Calls: .main ... FUN -> parse_block -> partition_chunk -> <Anonymous>
Execution halted
I spent way too much time looking for errors in my header YAML, forgetting that those #| comments are basically YAML now, too.
Not sure if it would be possible, but it would be awesome to have an error message that said something like Scanner error: while scanning the options in chunk 1, ... I was thinking of submitting a feature request on GitHub but wasn't sure if it would be a Quarto request, a knitr request, or something else.
Edit to add: I posted this on the Quarto discussion board on GitHub. That's probably the better place for this discussion.