option to hide child code warning

[jwijffels]

Hello,

I would like to be able to have the option to remove this warning at

knitr/R/block.R

Lines 59 to 62 in ff3d767

	if (!is_blank(params[['code']])) warning(
	"The chunk '", params$label, "' has the 'child' option, ",
	"and this code chunk must be empty. Its code will be ignored."
	)

which generates something like this:

Warning message:
In call_block(x) :
  The chunk 'xyz' has the 'child' option, and this code chunk must be empty. Its code will be ignored.

Reason of this is I would like to have the possibility to have a chunk which looks as follows

```{r, label=xyz, child = "children/kind.Rmd"}
f  <- knitr::purl(input = "children/kind.Rmd", output = tempfile(fileext = ".R"), quiet = TRUE)
sc <- paste(readLines(f), collapse = "\n")
source(exprs = parse(text = sc), print.eval = TRUE)

My children/kind.Rmd generates a table (flextable::flextable) which is printed to html. It looks like this

```{r}
library(flextable)
tab <- flextable(head(iris))
tab

If I render this, it will remove the R code in the chunk but still execute the children/kind.Rmd. While if I don't include the 3 lines to extract the R code from the child Rmd and evaluate it, the RStudio Visual editor will not show it. Only if I include the 3 lines of code.

Would you be open to have a small pull request which basically adds something like this: !is_blank(params[['code']]) && getOption("knitr.hide.child.code.warning", default = FALSE)

If so, what would be the preferred option name that I can use in this pull request? knitr.hide.child.code.warning?

thanks

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[yihui]

I guess you can put the code in another chunk with options eval = FALSE, include = FALSE, and leave the chunk with child empty. That way, you won't get the warning, and you can still run the code in RStudio.

[jwijffels]

That's also true of course but making it 2 chunks just to be able to show it in RStudio as the RStudio Visual Editor does not execute the child documents when you click on that run button creates code duplication.

[yihui]

Essentially what you really want is the ability to run a code chunk with the child option in the RStudio IDE. Ideally that should be supported by the IDE, but the IDE doesn't support the child option well currently, e.g., rstudio/rstudio#12208.

That said, I'm open to adding a global option to suppress this warning (perhaps a shorter option name like getOption('knitr.child.warning', TRUE)?). Please feel free to send a PR. Thanks!

[jwijffels]

Essentially what you really want is the ability to run a code chunk with the child option in the RStudio IDE.

Indeed, and I had the impression by skimming a bit online that this will not be supported in the near future. So that's why I ended up here.

Thanks. I'll create a pull request to add knitr.child.warning and keep the current default behaviour

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