From 02c61763876323e609a0f0706f51d630e39aafe4 Mon Sep 17 00:00:00 2001
From: John Bowdre <john@bowdre.net>
Date: Mon, 26 Feb 2024 16:24:58 -0600
Subject: [PATCH] fish: adjust prompt when inside a nix-shell

---
 home/features/cli/fish.nix | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/home/features/cli/fish.nix b/home/features/cli/fish.nix
index 885af5c..48b689d 100644
--- a/home/features/cli/fish.nix
+++ b/home/features/cli/fish.nix
@@ -27,6 +27,44 @@
     functions = {
       # Disable greeting
       fish_greeting = "";
+      fish_prompt = ''
+        set -l last_pipestatus $pipestatus
+        set -lx __fish_last_status $status # Export for __fish_print_pipestatus.
+        set -l normal (set_color normal)
+        set -q fish_color_status
+        or set -g fish_color_status red
+
+        # Detect if we're in a nix-shell
+        set -l nix_shell_info (
+          if test -n "$IN_NIX_SHELL"
+            echo -n "[nix-shell] "
+          end
+        )
+
+        # Color the prompt differently when we're root
+        set -l color_cwd $fish_color_cwd
+        set -l suffix '>'
+        if functions -q fish_is_root_user; and fish_is_root_user
+          if set -q fish_color_cwd_root
+            set color_cwd $fish_color_cwd_root
+          end
+          set suffix '#'
+        end
+
+        # Write pipestatus
+        # If the status was carried over (if no command is issued or if `set` leaves the status untouched), don't bold it.
+        set -l bold_flag --bold
+        set -q __fish_prompt_status_generation; or set -g __fish_prompt_status_generation $status_generation
+        if test $__fish_prompt_status_generation = $status_generation
+          set bold_flag
+        end
+        set __fish_prompt_status_generation $status_generation
+        set -l status_color (set_color $fish_color_status)
+        set -l statusb_color (set_color $bold_flag $fish_color_status)
+        set -l prompt_status (__fish_print_pipestatus "[" "]" "|" "$status_color" "$statusb_color" $last_pipestatus)
+
+        echo -n -s (prompt_login)' ' (set_color $color_cwd) (prompt_pwd) $normal (fish_vcs_prompt) $normal " "$nix_shell_info $prompt_status $suffix " "
+      '';
       ssh = "TERM=xterm command ssh $argv";
       # Rebuild home-manager
       switch-home = "home-manager switch -b backup --flake ${config.home.homeDirectory}/.dotfiles#$USER@$(hostname -s)";