Output colored red in `callr::r()`

[pwseo]

When using cli:: functions inside a callr::r invocation, output is always colored red (first noticed this using W Landau's targets package).
I'm not really sure this is even cli's fault, but I'm not experienced enought to debug this on my own.

Here's a screenshot of the problem:

[gaborcsardi]

cli uses message() which outputs to the standard error, and RStudio colours the standard error red.

When not using callr, cli figures out that it is in RStudio, so it outputs to the standard output to avoid this. But in the callr subprocess we have no way to tell if the output will be eventually in RStudio or not, so we cannot do that.

So there is not much we can do about this, apart from hoping that the red default will change.

[pwseo]

Oh, I see. Thank you for the clarification. I have a follow-up question though: Is there a way to configure cli to use stdout instead of stderr, then?

[gaborcsardi]

cli uses base::message() for its messages. I don't know if it is possible to make message() print to stdout.

[wlandau]

cli uses message() which outputs to the standard error, and RStudio colours the standard error red.

I also see the red text executing callr::r(\() cli::cli_text("abc"), show = TRUE) in an R process launched in a regular terminal outside the RStudio IDE. Am I missing something?

[wlandau]

I can remove the red if I redirect stderr to stdout, but I lose other colors as well. In the reprex below, I expect the check mark to be green, but it is white (both in the terminal and in RStudio Desktop.) How do I preserve the colors I would see outside the callr process? options(cli.color = TRUE) does not seem to work on my end.

tmp <- callr::r(
  \() {
    options(cli.color = TRUE)
    cli::cli_alert_success('abc')
  },
  show = TRUE,
  stderr = "2>&1"
)

✔ abc

I am using cli 3.6.2 and callr 3.7.3

[bakaburg1]

Hi! also messages colored with {crayon} lose the color information...

[wlandau]

I think I figured out why stderr = "2>&1" alone doesn't work: callr underestimates the number of colors that the terminal is capable of supporting:

cli::num_ansi_colors()
#> [1] 256
callr::r(\() cli::num_ansi_colors())
#> [1] 1

To preserve colors in text from callr, we need to:

1. Set stderr = "2>&1".
2. Set the cli.num_colors option to the correct number of colors.

This two-part solution works well, both in ordinary terminals and RStudio. When I try:

out <- callr::r(
  \() {
     options(cli.num_colors = 256)
     cli::ansi_palette_show()
  },
  show = TRUE,
  stderr = "2>&1"
)

I get the expected result:

I'm really happy about this because now I can preserve pretty colors in messages from targets. But I wonder if there is something either cli or callr can do to make the colors align by default.

[wlandau]

I just posted r-lib/callr#297. I think aligned color schemes (between parent and child) would be the most intuitive and expected default outcome from a user perspective.