Number of colors with active sink

[gaborcsardi]

r-lib/crayon#120 also affects cli, not very surprisingly.

[gaborcsardi]

Reprex:

sink(tmp <- tempfile())
cat(crayon::red("This is bad"), "\n")
cat(cli::col_red("Also bad"), "\n")
sink()
readLines(tmp)

[DavorJ]

If one uses sink() to split the stream, then there are two or more connections (of which one is usually a file that doesn't support ANSI sequences). In that case the cli::num_ansi_colors defaults to 1, ignoring all ANSI sequences supported by the terminal. In such case the user should probably choose the behavior with R_CLI_NUM_COLORS, but it is not documented. Hence the following suggestion:

?cli::num_ansi_colors mentions: "If you want to turn off ANSI colors, set the NO_COLOR environment variable to a non-empty value."

I would add there: "On the other hand, if you want to enforce a specific number of ANSI colors, set the R_CLI_NUM_COLORS environment variable."