Environment

• OS: NixOS 24.05.20240916.086b448 (Uakari)
• uutils version: 0.0.27
• Terminal: Alacritty
• Shell: zsh 5.9
• $TERM: alacritty
• $COLORTERM: truecolor

Issue

The ls command never shows colored output when TERM=alacritty.

Below is a screenshot comparing GNU coreutils 9.5 with uutils coreutils 0.0.27, both with option --color=always applied. Note how the output of the first is colored, while the latter is not.

To further prove the point, here is a comparison of the output (of a slightly different command, to keep it smaller) of the two utilities when passed to xxd.

❯ /nix/store/gvbxl47zf18ikwdii78pz2avaqizagk6-coreutils-full-9.5/bin/ls --color=always -l | xxd
00000000: 746f 7461 6c20 3132 0a64 7277 7872 2d78  total 12.drwxr-x
00000010: 722d 7820 3220 7369 6d6f 6e65 2075 7365  r-x 2 simone use
00000020: 7273 2034 3039 3620 5365 7020 3231 2031  rs 4096 Sep 21 1
00000030: 313a 3333 201b 5b30 6d1b 5b30 313b 3334  1:33 .[0m.[01;34
00000040: 6d50 6963 7475 7265 731b 5b30 6d0a 6472  mPictures.[0m.dr
00000050: 7778 722d 7872 2d78 2033 2073 696d 6f6e  wxr-xr-x 3 simon
00000060: 6520 7573 6572 7320 3430 3936 2053 6570  e users 4096 Sep
00000070: 2032 3120 3131 3a33 3320 1b5b 3031 3b33   21 11:33 .[01;3
00000080: 346d 5363 7269 7074 731b 5b30 6d0a 6472  4mScripts.[0m.dr
00000090: 7778 722d 7872 2d78 2033 2073 696d 6f6e  wxr-xr-x 3 simon
000000a0: 6520 7573 6572 7320 3430 3936 2053 6570  e users 4096 Sep
000000b0: 2032 3120 3131 3a30 3320 1b5b 3031 3b33   21 11:03 .[01;3
000000c0: 346d 5379 6e63 1b5b 306d 0a              4mSync.[0m.
❯ /nix/store/mi6rsqkw2w03mh56sfm9hjkis5c2bi5i-uutils-coreutils-0.0.27/bin/ls --color=always -l | xxd
00000000: 746f 7461 6c20 3132 0a64 7277 7872 2d78  total 12.drwxr-x
00000010: 722d 7820 3220 7369 6d6f 6e65 2075 7365  r-x 2 simone use
00000020: 7273 2034 3039 3620 5365 7020 3231 2031  rs 4096 Sep 21 1
00000030: 313a 3333 2050 6963 7475 7265 730a 6472  1:33 Pictures.dr
00000040: 7778 722d 7872 2d78 2033 2073 696d 6f6e  wxr-xr-x 3 simon
00000050: 6520 7573 6572 7320 3430 3936 2053 6570  e users 4096 Sep
00000060: 2032 3120 3131 3a33 3320 5363 7269 7074   21 11:33 Script
00000070: 730a 6472 7778 722d 7872 2d78 2033 2073  s.drwxr-xr-x 3 s
00000080: 696d 6f6e 6520 7573 6572 7320 3430 3936  imone users 4096
00000090: 2053 6570 2032 3120 3131 3a30 3320 5379   Sep 21 11:03 Sy
000000a0: 6e63 0a                                  nc.

Moreover, enforcing TERM=xterm-256color (or any value like TERM=xterm*) shows a colored output, although colors are not the same as those of GNU coreutils ls. See the screenshot below.

Analysis

Premise: I am not very familiar with Rust (not yet, alas).

Looking around for a root cause in the codebase, I've identified that the extract_color function is responsible for getting the value of the --color option. The first thing the function does is invoking is_color_compatible_term which looks up if the value of $TERM is in this list here. The list does not include alacritty which indeed seems to be the root cause.

To make a comparison, I quickly installed and tried also with Kitty. Since Kitty sets TERM=xterm-kitty, i.e. a xterm* type of value for $TERM, the colors do indeed appear (because of this match in the list).

Suggested solution

Since Alacritty do support colors (see its terminfo), I think it's totally safe, and desirable, to simply add alacritty to the list of compatible terminals. I clearly see that the list is taken directly from dircolors --print-database (or equivalent) but I do think it's fine to diverge in a sensible way like this. Actually, I'd suggest including alacritty*, instead of simply alacritty, so that alacritty-direct and alacritty+common are also supported.

If this simple change it's fine, I'll happily do a PR myself. Just let me know.