The Upcoming knitr v1.44: More Compatible with Quarto, and Locking opts_current

Update on 2023-09-12

knitr v1.44 is on CRAN now and I realized that locking opts_current might be a nontrivial breaking change (sorry about that). If your code or package is affected by the locked opts_current object and you run into an error “The object is read-only and cannot be modified”, you can call opts_current$lock(FALSE) to unlock it before you call opts_current$set(). I assume that you are modifying opts_current for a legitimate reason.

After coming back from vacation, I mainly spent my time on the knitr package maintenance. I will make a new release soon, and want to quickly highlight a few things in this post. For the full list of changes, please read the NEWS.md in the GitHub repo.

Working better with Quarto

The last version of knitr (v1.43) broke HTML Widgets in Quarto, which seems to have affected several users (sorry about that). This version has fixed the problem.

Error in `add_html_caption()`:
! unused argument (xfun::grep_sub("^[^<]*<[^>]+aria-labelledby[ ]*=[ ]*\"([^\"]+)\".*$", "\\1", x))

Other relatively minor improvements are:

• spin() supports the qmd format now, which is essentially the same as Rmd.

• The correct type of progress bar will be used when rendering Quarto documents in RStudio’s background jobs or build pane.

• All dashes in known knitr chunk option names will be automatically normalized to dots internally. Previously this job was done on Quarto’s side, but Quarto may miss certain chunk options. This change shouldn’t affect average users, but advanced users and developers may need to pay attention. For example, in knitr hooks, you should always use dots in chunk option names if the names are built-in in knitr. There are chunk options that are specific to Quarto, and these names will not be normalized, e.g., fig-responsive.

Locking opts_current

It has been documented for long that knitr::opts_current is assumed to be read-only, but some users still modify it via opts_current$set(). To prevent the accidental modification, this object will be locked when evaluating the code chunks. If you call opts_current$set() inside a code chunk, you will get an error.

I’d welcome any feedback on any of these changes. Thank you!