use comma and pregenerated nix-index

common/shell.nix

@@ -1,34 +1,24 @@
-{ config, pkgs, ... }:
+{ config, lib, pkgs, ... }:
 
 # Improvements to the default shell
-# - use nix-locate for command-not-found
+# - use nix-index for command-not-found
 # - disable fish's annoying greeting message
 # - add some handy shell commands
 
-let
-  nix-locate = config.inputs.nix-locate.packages.${config.currentSystem}.default;
-in {
-  programs.command-not-found.enable = false;
-
-  environment.systemPackages = [
-    nix-locate
+{
+  environment.systemPackages = with pkgs; [
+    comma
   ];
 
+  # nix-index
+  programs.nix-index.enable = true;
+  programs.nix-index.enableFishIntegration = true;
+  programs.command-not-found.enable = false;
+
   programs.fish = {
     enable = true;
 
-    shellInit = let
-      wrapper = pkgs.writeScript "command-not-found" ''
-        #!${pkgs.bash}/bin/bash
-        source ${nix-locate}/etc/profile.d/command-not-found.sh
-        command_not_found_handle "$@"
-      '';
-    in ''
-      # use nix-locate for command-not-found functionality
-      function __fish_command_not_found_handler --on-event fish_command_not_found
-          ${wrapper} $argv
-      end
-
+    shellInit = ''
       # disable annoying fish shell greeting
       set fish_greeting
     '';
@@ -43,4 +33,18 @@ in {
     io_rand_read = "nix run nixpkgs#fio -- --name TEST --eta-newline=5s --filename=temp.file --rw=randread --size=2g --io_size=10g --blocksize=4k --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=32 --runtime=60 --group_reporting; rm temp.file";
     io_rand_write = "nix run nixpkgs#fio -- --name TEST --eta-newline=5s --filename=temp.file --rw=randrw --size=2g --io_size=10g --blocksize=4k --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=1 --runtime=60 --group_reporting; rm temp.file";
   };
+
+  nixpkgs.overlays = [
+    (final: prev: {
+      # comma uses the "nix-index" package built into nixpkgs by default.
+      # That package doesn't use the prebuilt nix-index database so it needs to be changed.
+      comma = prev.comma.overrideAttrs (old: {
+        postInstall = ''
+          wrapProgram $out/bin/comma \
+            --prefix PATH : ${lib.makeBinPath [ prev.fzy config.programs.nix-index.package ]}
+          ln -s $out/bin/comma $out/bin/,
+        '';
+      });
+    })
+  ];
 }