Quarto R chunks do not display a consistent order when printing warnings

[ColinFay]

Bug description

The standard behaviour for R function is to print the warning after everything in the function is computed:

hello_then_warn <- function(){
  warning("Warning")
  print("Hello world")
}
hello_then_warn()

If I put this function in a Qmd and render it, the warning is before the "Hello world"

If I use the option chunk_output_type: console in the notebook, the order is correct

If I use the option chunk_output_type: inline, the order is different

Steps to reproduce

Create a qmd with the following function in an R chunk

hello_then_warn <- function(){
  warning("Warning")
  print("Hello world")
}
hello_then_warn()

Actual behavior

The warning message is before the print

Expected behavior

The warning message is after the print

Your environment

• RSTUDIO server 2025.05.1 Build 513

[cscheid]

I don't quite understand if this is an issue with RStudio or quarto-cli. (@cderv, can you help?)

In any case, if the issue is with quarto-cli, then it should go to https://github.com/quarto-dev/quarto-cli. If it's with RStudio, it should go to https://github.com/rstudio/rstudio

[ColinFay]

@cscheid fwiw I've got the same behavior when rendering a qmd in VSCode so I suppose that's not linked to RStudio itself?

[cscheid]

This is a bit clearer, thanks. I'll still leave it to Christophe to make a call whether this is a bug or not, but it's clearly something for quarto-cli. I'll transfer the issue.

[mcanouil]

That's a knitr behaviour.
The same thing will happen in RMarkdown.

And results: hold won't work for warnings/messages/errors.

[mcanouil]

That's actually how evaluate works:

evaluate(), which evaluates each expression produced by parse_all(), tracking all output, messages, warnings, and errors as their occur, and interleaving them in the correct order with the original source and value of the expression.

evaluate::evaluate(c(
  'hello_then_warn <- function() { warning("Warning"); print("Hello world") }',
  'hello_then_warn()'
))

<evaluation>
Source code: 
  hello_then_warn <- function() { warning("Warning"); print("Hello world") }
Source code: 
  hello_then_warn()
Condition: 
  Warning in hello_then_warn():
  Warning
Text output: 
  [1] "Hello world"

The only way to change this behaviour I can think of is to define a new hook for warnings to hold on them until the end.

• https://bookdown.org/yihui/rmarkdown-cookbook/output-hooks.html