crayon:::has_color() returns FALSE when an output sink is active about crayon

[gaborcsardi]

The idea is that you will print those strings to stdout ASAP, and if stdout does not support color, then we don't use the ANSI escape codes. So this is as designed.

Most programs work the same way, e.g. just try

ls -G
ls -G > /tmp/x

If you want to force the ANSI sequences, use the crayon.enabled. and crayon.colors options. E.g.

withr::with_options(
  c(crayon.enabled = TRUE, crayon.colors = 256),
  red("I am red")
)

[HenrikBengtsson]

I see; makes sense.

Then a follow up, shouldn't there be test against stderr() if you "plan" to print to stderr? I understand this is not easy to detect / support automatically; maybe an argument output = "stdout"?

FYI, I bumped into this when trying to conditionally display yellow("1 output sink") to a customized prompt function. I did find the workaround where I do if (crayon:::has_color()) options(crayon.enabled = TRUE) when I first set up the prompt during .Rprofile startup (where I can safely assume no sinks are active).

[gaborcsardi]

maybe an argument output = "stdout"?

argument to what function?

Maybe it could be an option, e.g. crayon.output, but that will be cumbersome to change every time...

[HenrikBengtsson]

maybe an argument output = "stdout"?

argument to what function?

agree == "maybe" ;) In worst case, it's needed for all functions calling has_color() ... very tedious to use.

Could such an option be encapsulated in a convenient for_stderr() wrapper, e.g. for_stderr(red("foo"))? (not sure if with_stderr() is good here).

[gaborcsardi]

for_stderr is a good idea. How about calling it color_stderr ?

We could also have with_color to shorten the with_options call above.

[HenrikBengtsson]

color_stderr() is better, but like with_color() even more. Not sure what the argument / option name should be, e.g. target, type (cf. sink()), ...?

For the output target, can see something like the following use cases:

• with_color(..., target = "stdout"))
• with_color(..., target = "stderr"))
• with_color(..., target = c("stdout", "stderr"))) - outputting to both(?)
• with_color(..., target = "prompt")) - neither stdout nor stderr, but prompt and readline-ish output (non-sinkable)
• with_color(..., target = "none")) - disable coloring
• with_color(..., target = "always")) - enable coloring regardless of support(?)

[gaborcsardi]

Yeah, sg. like that.

[gaborcsardi]

OK, I decided not to do this for the next patch release. It is probably not commonly needed, and I am not yet sure what would be the right way to do. For now, please force color as a workaround.