Please give the output of locale

locale
LANG=C
LC_CTYPE="C"
LC_NUMERIC="C"
LC_TIME="C"
LC_COLLATE="C"
LC_MONETARY="C"
LC_MESSAGES="C"
LC_PAPER="C"
LC_NAME="C"
LC_ADDRESS="C"
LC_TELEPHONE="C"
LC_MEASUREMENT="C"
LC_IDENTIFICATION="C"
LC_ALL=

That's your issue. Please set the locale to something that can handle unicode, like one of the ".UTF-8" locales.

See https://wiki.archlinux.org/index.php/Locale. Most likely you need to generate one, then configure it in /etc/locale.conf.

This is still not a great failure mode - what it's supposed to do is to replace the unknown characters with "?", which is also what happens in my prompt, but for some reason the sorin prompt's

function fish_prompt; echo -n (set_color red)'❯'(set_color yellow)'❯'(set_color green)'❯ '; end

doesn't.

Thank you @faho indeed that was the issue. Changing the locale to en_US.UTF-8 solved it.

Should I close the issue or do you prefer to keep it open to track the failure mode not changing the unknown characters with "?" ?

Let's keep it open, I'm bisecting.

Bisects to 5134949. Well, I say that. Unfortunately it had a crash bug with a C locale which was only fixed by 2b0b3d3, but cherry-picking that on top makes it not crash yet fail to output.

cc @ridiculousfish Mind taking a look? The issue is that

function fish_prompt; echo 😃; end

or other non-ascii chars causes no visible output with a C locale.

Okay, it's actually 2b0b3d3.

Fixed in master with 6237a24, 3.1.1 with 1a063fe.

(I forgot to include the magical "fixes" comment)