nix - increase compatibility for command-not-found

- fallback to `nix-index` on darwin
- also simulate `command-not-found` with alias

nix/home/programs/default.nix

@@ -1,7 +1,7 @@
 { config, pkgs, ... }:
 
 let
-  shells = import ./shells.nix { config = config; };
+  shells = import ./shells.nix { config = config; pkgs = pkgs; };
   terminals = import ./terminals.nix { pkgs = pkgs; };
 in
 {

nix/home/programs/shells.nix

@@ -1,4 +1,4 @@
-{ config, ... }:
+{ config, pkgs, ... }:
 
 let
   env-vars = config.home.sessionVariables;
@@ -20,7 +20,7 @@ in
   # I don't like that these goes after $PATH not before - let me think about a workaround
   # and of course the related issues can be found here! - https://github.com/nix-community/home-manager/issues/3324
   home.sessionPath = [
-    "$XDG_CONFIG_HOME/dfs-rhc/bin/path/default"
+    ''''${XDG_CONFIG_HOME}/dfs-rhc/bin/path/default''
   ];
 
   # only the super basic ones that should be shared across shells
@@ -30,7 +30,15 @@ in
     printpath = ''echo ''${PATH} | tr ":" "\n"'';
   };
 
-  programs.command-not-found.enable = true;
+  programs.command-not-found = {
+    enable = ! pkgs.stdenv.isDarwin;
+  };
+
+  # fallback to nix-index on darwin in place of command-not-found
+  # https://github.com/bennofs/nix-index#usage-as-a-command-not-found-replacement
+  programs.nix-index = {
+    enable = pkgs.stdenv.isDarwin;
+  };
 
   programs.bash = {
     # https://nix-community.github.io/home-manager/options.html#opt-programs.bash.enable

zsh/my_addons/aliases

@@ -442,3 +442,6 @@ inspect-home-manager ()
 }
 
 alias inspect-bash='/bin/bash -lixc exit 2>&1 | sed -n "s/^+* \(source\|\.\) //p"' # via https://stackoverflow.com/a/65922714/1570165
+
+# mimic `command-not-found` via `nix-index` shell hook when it's not available
+test -z "${commands[command-not-found]}" && alias command-not-found='bash -ic '